Laser Beam Machining

Abstract Abstrak

An overview is given of the state of the art of laser beam machining in general with special emphasis on applications of short andGambaran yang diberikan dari keadaan seni mesin sinar laser secara umum dengan penekanan khusus pada aplikasi pendek dan ultrashort lasers.ultrashort laser. In laser welding the trend is to apply optical sensors for process control. Dalam pengelasan laser tren adalah untuk menerapkan sensor optik untuk pengendalian proses. Laser surface treatment is mostly used to apply Laser pengobatan permukaan sebagian besar digunakan untuk menerapkan corrosion and wear resistant layers, but also for repair of engine and machine parts.korosi dan keausan lapisan tahan, tetapi juga untuk perbaikan mesin dan bagian mesin. In micro-machining, shorter pulses reduce heat-affected Dalam mikro-mesin, pulsa pendek mengurangi panas yang terkena dampak damage of the material and opens new ways for nanometer accuracy.kerusakan material dan membuka cara-cara baru untuk akurasi nanometer. Even 40 years after the development of the laser there is a lot of Bahkan 40 tahun setelah pengembangan laser ada banyak effort in developing new and better performing lasers.usaha dalam mengembangkan laser dengan performa dan lebih baik. The driving force is higher accuracy at reasonable cost, which is realised by compact Kekuatan pendorong adalah akurasi yang lebih tinggi dengan biaya murah, yang diwujudkan dengan kompak systems delivering short laser pulses of high beam quality.sistem memberikan pulsa laser pendek berkualitas balok tinggi. Another trend is the shift towards shorter wavelengths, which are better absorbed Kecenderungan lain adalah pergeseran ke arah panjang gelombang yang lebih pendek, yang lebih baik diserapby the material and which allows smaller feature sizes to be produced. oleh material dan ukuran yang memungkinkan fitur yang lebih kecil untuk diproduksi. Examples of new products, which became possible by this technique, Contoh produk baru, yang menjadi mungkin dengan teknik ini are given.diberikan. The trends in miniaturisation as predicted by Moore and Taniguchi are expected to continue over the next decade too thanks to Tren dalam miniaturisasi seperti yang diperkirakan oleh Moore dan Taniguchi diperkirakan akan terus selama dekade berikutnya terlalu berkat short and ultrashort laser machining techniques.pendek dan teknik mesin laser ultrashort.

© 2004 Elsevier BV All rights reserved. © 2004 Elsevier BV All rights reserved.

Keywords: Laser beam machining (LBM); Welding; Surface treatment; Micro-machining; Ablation Keywords: mesin Laser beam (LBM); Pengelasan, pengobatan Permukaan; Micro-mesin; Ablation

1. 1. Introduction Pengenalan

Photons are in this century. Foton dalam abad ini. They are replacing electrons Mereka menggantikan elektron

as the favourite tool in modern industry. sebagai alat favorit dalam industri modern. Light is used for Cahaya yang digunakan untuk

everything from eye surgery to telephone technology and segala sesuatu dari operasi mata dengan teknologi telepon dan

materials processing. bahan pengolahan. Photons are applied in an increasing Foton diterapkan dalam meningkatkan

number of topics addressed by this ISEM 14. jumlah topik yang dibahas oleh ISEM 14. An important Yang penting

property of light is that it has no volume, photons have no properti cahaya adalah bahwa ia memiliki volume tidak, foton tidak memiliki

charge, so when concentrated into a very small space, they biaya, jadi ketika terkonsentrasi dalam ruang yang sangat kecil, mereka

do not repulse each other like negative charged electrons do. tidak memukul mundur satu sama lain seperti elektron bermuatan negatif lakukan.

This is an important property especial for ultrashort machin- Ini adalah sifat penting utama untuk ultrashort Machin-

ing. ing. Light moves through space as a wave, but when it en- Cahaya bergerak melalui ruang sebagai sebuah gelombang, tetapi ketika en-

counters matter it behaves like a particle of energy, a photon. counter peduli itu berperilaku seperti sebuah partikel energi, foton.

Not all photons have the same amount of energy. Tidak semua foton memiliki jumlah energi yang sama. The visi- The-Visi

ble part of the spectrum contains wavelengths from 400 to bel bagian dari spektrum panjang gelombang dari 400 berisi untuk

750 nm. 750 nm. Radiation below 400 nm includes the harmful fre- Radiasi di bawah 400 nm termasuk berbahaya fre-

quencies of UV and X-rays, while above 750 nm the invisi- quencies UV dan sinar-X, sementara di atas 750 nm invisi-

ble infrared, microwave and radio frequencies are included. ble inframerah, microwave dan frekuensi radio yang disertakan.

The energy of photons is E = hν . Energi dari foton adalah E = hν. For the visible 500 nm Untuk 500 nm terlihat

wavelength this is 4 × 10 panjang gelombang ini adalah 4 × 10

−19 -19

J or 2.5 eV per photon, which J atau eV 2,5 per foton, yang

is not enough to break the chemical bonds in the material, tidak cukup untuk memecahkan ikatan kimia dalam materi,

which requires 3–10 eV. yang membutuhkan 3-10 eV. In the laser materials processing Dalam pengolahan bahan laser

this can be overcome in different ways. hal ini bisa diatasi dengan cara yang berbeda. The first solution is Solusi pertama adalah

E-mail address: [email protected] (J. Meijer). E-mail: j.meijer @ utwente.nl (J. Meijer).

simply heating the material by absorption of laser energy, hanya pemanasan bahan oleh penyerapan energi laser,

which is a thermal or pyrolytic process. yang merupakan proses termal atau pirolitik. Secondly higher Kedua tinggi

energy photons (UV) can be used with photon energies of energi foton (UV) dapat digunakan dengan energi foton

3–7 eV, which is used to break the chemical bonds directly 3-7 eV, yang digunakan untuk memecahkan ikatan kimia secara langsung

(especially plastics). (Terutama plastik). This is a photolytic process. Ini adalah proses photolytic. For met- Untuk bertemu-

als even more energy is required (up to five times the sub- als energi bahkan lebih diperlukan (sampai lima kali sub-

limation energy of about 4 eV for most metals). limation energi sekitar 4 eV untuk sebagian besar logam). The third Ketiga option is using lasers that deliver so many photons on a timepilihan adalah menggunakan laser yang memberikan begitu banyak foton pada suatu waktu

that electrons are hit by several photons simultaneously. bahwa elektron yang terkena foton secara bersamaan. Ab- Ab-

sorption of multi-photons has the same result as single high penyerapan multi-foton memiliki hasil yang sama seperti tinggi tunggal

energetic photons. foton energik. In this case the photon energy, thus the Dalam hal ini energi foton, sehingga

wavelength, is less important because energy is transferred panjang gelombang, kurang penting karena energi yang ditransfer

by multi-photons simultaneously. oleh multi-foton secara bersamaan. This is a reason that such Ini adalah alasan bahwa seperti

lasers are preferable operated in the visible part of the spec- laser lebih disukai dioperasikan di bagian yang terlihat dari spec-

trum with relatively simple optics. spektrum dengan optik relatif sederhana. In this paper, some com- Dalam tulisan ini, beberapa com-

ments are made about developments in welding and surface supplemen adalah dibuat tentang perkembangan dalam pengelasan dan permukaan

treatment and deals in more detail with the challenges of pengobatan dan penawaran di lebih rinci dengan tantangan

applications using short and ultrashort pulsed lasers. aplikasi yang menggunakan laser berdenyut pendek dan ultrashort.

2. 2. Laser welding Laser welding

After the maturation of laser cutting also welding is be- Setelah pematangan pemotongan laser juga pengelasan adalah menjadi-

coming everyday technology. datang teknologi sehari-hari. For 10 years people said 'we Selama 10 tahun orang mengatakan 'kita

can weld any material, as long as it is stainless steel'. dapat mengelas bahan apapun, asalkan itu adalah stainless steel '. Now Sekarang

indeed almost all materials can be laser welded. memang hampir semua bahan dapat laser dilas. Challenges Tantangan

0924-0136/$ – see front matter © 2004 Elsevier BV All rights reserved. 0924-0136 / $ - melihat hal depan Elsevier BV © 2004 All rights reserved.

doi:10.1016/j.jmatprotec.2004.02.003 doi: 10.1016/j.jmatprotec.2004.02.003

Page 2 Halaman 2

J. Meijer / Journal of Materials Processing Technology 149 (2004) 2–17 J. Meijer / Jurnal Teknologi Pengolahan Bahan 149 (2004) 2-17

3 3

Fig. Gambar. 1. 1. Laser welded parts for a TV electron gun (Philips CFT). Laser dilas bagian untuk TV elektron gun (Philips CFT).

are found in the area of beam and product handling. ditemukan di daerah balok dan penanganan produk. In the Dalam

high volume market, eg in the electronics industry special volume tinggi pasar, misalnya di industri elektronik khusus

machines are built around one product for just a few welds mesin dibangun sekitar satu produk untuk hanya beberapa las

( . ( Gambar. 1) . In such applications, the required accuracy for laser Dalam aplikasi tersebut, akurasi yang diperlukan untuk laser

welding is built-in in the machine. pengelasan adalah built-in dalam mesin.

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The same is seen in welding of tailor made blanks, which Hal yang sama terlihat dalam pengelasan kosong dibuat khusus, yang

become more and more popular in car manufacturing. menjadi lebih dan lebih populer di bidang manufaktur mobil. It is Hal ini

the production of blanks of steel used to press sheet metal produksi kosong baja digunakan untuk menekan lembaran logam

parts like doors, hoods, suspensions, etc. The sheet elements bagian-bagian seperti pintu, kerudung, suspensi, dll elemen lembar

are chosen of different thickness or different strength to meet dipilih dari ketebalan yang berbeda atau kekuatan yang berbeda untuk memenuhi

the requirements of the composed part. persyaratan bagian terdiri. Here the welds are Berikut lasan yang

mostly linear while the accuracy is obtained by the design sebagian besar linear sedangkan akurasi diperoleh dengan desain

of the machine and the clamping tools. dari mesin dan alat klem. In this area there is Di daerah ini ada

trend to inspect each weld by CCD cameras directly after tren untuk memeriksa mengelas masing-masing oleh kamera CCD langsung setelah

welding and even to observe the seam before in order to pengelasan dan bahkan untuk mengamati jahitan sebelum dalam rangka untuk

correct for instance for uneven cutting edges. yang benar misalnya untuk memotong tepi yang tidak rata. In automotive Dalam otomotif

applications, in special in bodywork, it is hard to meet the aplikasi, dalam khusus di bodywork, sulit untuk memenuhi

tolerances. toleransi. This problem is often solved by the construction, Masalah ini sering diselesaikan dengan konstruksi,

using overlap seams, which are more faults tolerant. menggunakan lapisan tumpang tindih, yang lebih toleran kesalahan. The Para

effects of some errors in are shown in efek dari beberapa kesalahan dalam ditunjukkan dalam Gambar. Gaps should be 2. Kesenjangan harus

restricted to 10–20% of the sheet thickness. dibatasi untuk 10-20% dari ketebalan lembar. The process is Proses ini

more tolerant for displacement tolerances. lebih toleran untuk toleransi perpindahan. Aluminium is less Aluminium kurang

sensitive for adjustment errors, probably due to the better sensitif untuk kesalahan penyesuaian, mungkin karena lebih baik



heat conductivity. konduktivitas panas.

A new area is welding of dissimilar materials like steel and Sebuah daerah baru adalah pengelasan bahan berbeda seperti baja dan

aluminium, which is known to be impossible in conventional aluminium, yang dikenal menjadi mustahil di konvensional

welding. pengelasan. Gambar. shows an overlap weld of a 1 mm thick 3 menunjukkan las tumpang tindih dari 1 mm tebal

steel plate to aluminium. pelat baja dengan aluminium. For a good wettability the material Untuk keterbasahan baik materi

Fig. Gambar. 2. 2. Effect of tolerances in laser welding of aluminium. Pengaruh toleransi dalam pengelasan laser dari aluminium.

Fig. Gambar. 3. 3. Laser welding of steel (top) on aluminium. Laser pengelasan baja (atas) pada aluminium.

Fig. Gambar. 4. 4. Sensors can be fully integrated in a laser-robot welding system. Sensor dapat sepenuhnya terintegrasi dalam sistem pengelasan laser-robot.

should be free from oxides before welding and the speed and harus bebas dari oksida sebelum pengelasan dan kecepatan dan

temperature should be balanced to reduce the intermetallic suhu harus seimbang untuk mengurangi intermetalik

layer (less than 5 m). lapisan (kurang dari 5 m). It is shown that the aluminium flows Hal ini menunjukkan bahwa aluminium mengalir

nicely over the steel. baik dari baja. This type of welds are of growing Jenis las yang tumbuh

interest in shipbuilding and automotive applications. kepentingan dalam pembuatan kapal dan aplikasi otomotif.

The high welding speeds in laser welding, eg 100 mm/s Kecepatan pengelasan yang tinggi dalam pengelasan laser, misalnya 100 mm / s

and the small tolerances require a high degree of automa- dan toleransi kecil membutuhkan tingkat tinggi automa-

tion. tion. In particular robots are applied more and more. Secara khusus robot diterapkan lebih dan lebih. De- De-

velopments are ongoing on real time process sensing and velopments sedang berlangsung pada penginderaan proses real time dan

control as well as on-line quality inspection. kontrol serta on-line pemeriksaan mutu. Postma et al. Postma et al.



[1] have developed a system for measuring and control the telah mengembangkan suatu sistem untuk mengukur dan mengendalikan

welding process by sensing the plume radiation optimising proses pengelasan dengan merasakan radiasi membanggakan mengoptimalkan

the welding speed. kecepatan pengelasan. Such a systems can be fully integrated Seperti sistem dapat terintegrasi

in laser-robot welding systems with the sensor measuring di laser-robot las dengan sistem pengukuran sensor

through the same optical fibre as used for beam delivery melalui serat optik yang sama seperti yang digunakan untuk pengiriman balok

( ( Gambar. 4).

3. 3. Laser cladding and alloying Laser cladding dan paduan

Lasercladden is used to improve the surface quality by Lasercladden digunakan untuk meningkatkan kualitas permukaan dengan

applying a hard or a corrosion resistant layer on a product of menerapkan keras atau lapisan tahan korosi pada produk

cheap or better to machine material. murah atau lebih baik untuk bahan mesin. The common technique Teknik umum

is to create a shallow melt pool by a defocussed laserbeam adalah untuk membuat kolam lelehan dangkal oleh laserbeam defocussed

and supply metal powder in that pool using an inert gas flow. dan pasokan serbuk logam dalam kolam menggunakan aliran gas inert.

Examples are shown in Contoh ditunjukkan pada Gambar. left the cladding of a roller 5, meninggalkan kelongsong dari roller

wheel for sheet metal forming, centre cross section of the roda untuk membentuk lembaran logam, bagian tengah silang dari

wheel and right a diesel engine crankshaft. roda dan hak crankshaft mesin diesel.

The last application restoring (costly) products by ap- Aplikasi terakhir memulihkan (mahal) produk dengan ap-

plying fresh material on worn out or corroded products is plying bahan segar pada produk aus atau berkarat adalah

applied on diesel engine parts like cylinder heads, valves, diterapkan pada bagian-bagian mesin diesel seperti kepala silinder, katup,





Halaman 3

4 4


Fig. Gambar. 5. 5. Examples of laser cladding. Contoh cladding laser.

shafts, etc. Further applications are for the chemical indus- shaft, dll aplikasi lebih lanjut untuk kimia indus-

try, mining, marine and military applications. mencoba, aplikasi pertambangan, kelautan dan militer.

This technique can be applied also to form new prod- Teknik ini dapat diterapkan juga untuk bentuk baru prod-

ucts (prototypes) directly from a CAD file By varying ucts (prototipe) langsung dari file CAD [2]. Dengan memvariasikan

the powder composition material properties can be changed sifat komposisi serbuk material dapat diubah

continuously during the build-up. terus menerus selama membangun-up. In this way products made Dengan cara ini produk yang dibuat

from graded materials are obtained. dari bahan bergradasi diperoleh.

As well in laser welding as in laser cladding CO Seperti juga dalam pengelasan laser sebagai kelongsong Laser CO

2 2

-lasers -Laser

are used because of their high power better efficiency and digunakan karena efisiensi daya tinggi lebih baik dan

good beam quality. baik kualitas balok. Nowadays more and more Nd:YAG Saat ini lebih dan lebih Nd: YAG

lasers are used because they are easily combined with laser digunakan karena mereka mudah dikombinasikan dengan

robots. robot. Further also YAG lasers become available at higher YAG laser lebih lanjut juga tersedia pada lebih tinggi

power levels. tingkat daya. The reason for a poor beam quality of high Alasan untuk kualitas yang buruk balok tinggi

power Nd:YAG lasers is the thermal load of the laser rod daya Nd: YAG laser adalah beban termal batang Laser


resulting in thermal expansion of the rod, in the centre more mengakibatkan ekspansi termal batang, di pusat lebih

than at the peripheral which causes optical aberrations in daripada di perifer yang menyebabkan penyimpangan optik di

the laser cavity. rongga laser. The laser industry is solving that by differ- Industri laser adalah memecahkan bahwa dengan berbeda-

ent ways. ent cara. The first solution was using diode lasers to pump Solusi pertama adalah dengan menggunakan dioda laser untuk memompa

the laser, as a next step the laser rod is shortened to just a laser, sebagai langkah berikutnya batang laser disingkat menjadi hanya

thin disk which can be effectively cooled over the whole tipis disk yang dapat secara efektif didinginkan atas seluruh

diameter. diameter. This has resulted in the Nd:YAG disk laser which Hal ini telah mengakibatkan Nd: YAG laser disk yang

in power ranges up to 4 kW is coming on the market. dalam rentang daya hingga 4 kW yang datang di pasar. An- An-

other promising solution is the opposite way by stretching solusi yang menjanjikan lainnya adalah cara yang berlawanan dengan peregangan

the rod into a long thin fibre. batang menjadi serat tipis panjang. Techniques as multimode Teknik seperti multimode

fibre coupling of diode pump light into the active (single kopling serat cahaya dioda pompa ke aktif (tunggal

Fig. Gambar. 6. 6. Overview of laser machining processes. Sekilas proses mesin laser. The 'conventional' laser processes are found around the line of 1 kJ/cm The 'konvensional' proses laser ditemukan di sekitar garis 1 kJ / cm

2 2

. . The dotted line indicates the Garis putus-putus menunjukkan

melt boundary of metal. lelehan batas logam. Ultrashort processes require less energy per square centimetre in general. Proses ultrashort membutuhkan energi lebih sedikit per sentimeter persegi pada umumnya.

mode) fibre, which originates from the telecom industry, modus) serat, yang berasal dari industri telekomunikasi,

enables multi-kilowatt input by thousands of (few Watts) memungkinkan multi-kilowatt masukan oleh ribuan (Watt sedikit)

diode lasers. dioda laser. Now industrial fibre lasers up to 10 kW output Sekarang industri serat laser hingga 10 kW keluaran

and 25% efficiency are coming on the market. dan efisiensi 25% yang datang di pasar. It is expected Diharapkan

that such systems which require less floor space (≈0.5 m bahwa seperti sistem yang membutuhkan ruang lantai kurang (≈ 0,5 m

2 2

for a 4 kW system) will cause a breakthrough in high power untuk sistem kW 4) akan menyebabkan terobosan dalam daya tinggi

applications like laser welding and laser cladding. aplikasi seperti pengelasan laser dan cladding laser.

4. 4. Laser–material interactions, short and ultrashort Laser-materi interaksi, pendek dan ultrashort

Since the invention of the laser there has been a constant Sejak penemuan laser telah ada konstan

development to shorter pulse times. pengembangan untuk kali pulsa lebih pendek. Only a few years ago Hanya beberapa tahun yang lalu

10 ns pulses were the shortest obtainable but now femtosec- 10 ns pulsa adalah terpendek diperoleh tapi sekarang femtosec-

ond lasers are applied and even shorter pulses can be ob- Metode kedua laser diterapkan dan bahkan pulsa pendek dapat ob-

tained in the lab. dipertahankan di laboratorium. Therefore, we will discuss first what is Oleh karena itu, kita akan membahas terlebih dahulu apa yang

short from the viewpoint of the laser. singkat dari sudut pandang laser.

Like very long distances can be expressed in light-years Seperti jarak yang sangat jauh dapat dinyatakan dalam tahun cahaya

we can express very short times in light-distances, that is kita dapat mengekspresikan kali sangat pendek dalam terang-jarak, yaitu

the distance a light wave or a photon travels during that jarak gelombang cahaya atau foton perjalanan selama

short time. waktu singkat. This distance is for 100 fs pulse only 30 m. Jarak ini adalah untuk 100 fs pulsa hanya 30 m.

In Dalam Gambar. these light-distances are shown in relation to 6, cahaya-jarak yang akan ditampilkan dalam kaitannya dengan

the laser machining processes. mesin laser memproses. For very short femtosecond Untuk femtosecond sangat singkat



pulses this distance is in the order of the wavelength of the pulsa jarak ini dalam urutan panjang gelombang

light! cahaya!

Page 4 Halaman 4


5 5

The question how short is short enough can also be ap- Pertanyaan betapa singkat cukup pendek juga dapat ap-

proached from the viewpoint of the applications. proached dari sudut pandang aplikasi. Chen and Chen dan

Liu ompared different pulse widths and concluded that Liu [3] c ompared lebar pulsa yang berbeda dan menyimpulkan bahwa

shorter pulses produce better quality but at higher cost. pulsa lebih pendek menghasilkan kualitas yang lebih baik tetapi dengan biaya yang lebih tinggi. The Para

question what is short and what is ultrashort can be discussed pertanyaan apa yang pendek dan apa yang ultrashort dapat dibahas

also from the viewpoint of the material. juga dari sudut pandang materi. The material is sub- Materi yang adalah sub-

jected to a beam of photons coming from outside which is diproyeksikan untuk seberkas foton yang datang dari luar yang

absorbed in a skin layer . diserap di lapisan kulit. The photons are absorbed in that Foton diserap dalam

skin layer by the free electrons, in about 1 fs (10 lapisan kulit oleh elektron bebas, sekitar 1 fs (10

−15 -15

s). s). The Para

relaxation time of the electrons is about 1 ps (10 waktu relaksasi elektron sekitar 1 ps (10

−12 -12

s). s). Dur- Dur-


ing that time the energy is stored in the electrons, after the ing waktu itu energi disimpan dalam elektron, setelah

relaxation time it is converted into heat. waktu relaksasi itu dikonversi menjadi panas.

The intensity of the incoming beam is expressed by I Intensitas sinar yang masuk dinyatakan oleh I

0 0

. .

The decrease of the laser intensity in the depth is given by Penurunan intensitas laser secara mendalam diberikan oleh

I Aku

x x

= I = Aku

0 0

e e

− αx - Αx

where α the optical absorptivity of the material di mana α absorptivitas optik bahan

and x the depth into the material. dan x kedalaman ke dalam bahan. An important quantity is Kuantitas penting adalah

the penetration depth δ ( δ = 2 /α ) in which almost all laser kedalaman penetrasi δ (δ = 2 / α) di mana hampir semua Laser

energy is absorbed. energi diserap. This optical penetration depth is for Ini kedalaman penetrasi optik adalah untuk

metals in the order of 10 nm. logam di urutan 10 nm. It means that the laser energy Ini berarti bahwa energi laser

heats a 10 nm thick layer of metal in 1 ps. memanaskan lapisan tebal 10 nm logam di 1 ps. This heat will Panas ini akan

diffuse from that skin layer to the bulk. berdifusi dari bahwa lapisan kulit untuk bulk. The diffusion depth Kedalaman difusi

is expressed by d = dinyatakan dengan d =

√ √

4 at with a as the thermal diffusivity 4 pada dengan sebagai difusivitas termal

and t the diffusion time. dan t waktu difusi. In case of steel we obtain in 10 fs Dalam kasus baja yang kita peroleh dalam 10 fs

a diffusion depth of 1 nm while during a 1 ps pulse the heat kedalaman difusi 1 nm sementara selama 1 id pulsa panas

diffuses over 10 nm. berdifusi lebih dari 10 nm. Taking the results together than we see Mengambil hasil bersama-sama daripada yang kita lihat

that: bahwa:

• it takes 1 ps to convert laser energy into heat, • butuh 1 ps untuk mengubah energi laser menjadi panas,

• this takes place in a 10 nm thick skin layer, • ini terjadi dalam lapisan kulit 10 nm tebal,

• the diffusion depth for 1 ps is also 10 nm. • kedalaman difusi untuk 1 ps juga 10 nm.

From these results we consider a pulse as ultrashort when Dari hasil ini kita anggap sebagai ultrashort pulsa saat

the (thermal) diffusion depth during the pulse is in the same tersebut (panas) difusi mendalam selama denyut nadi di sama

order or less than the skin layer depth (optical penetration rangka atau kurang dari kedalaman lapisan kulit (penetrasi optik

depth). kedalaman). The optical penetration depth depends on the mate- Kedalaman penetrasi optik tergantung pada pasangan-

rial and the laser wavelength. Rial dan panjang gelombang laser. The diffusion depth depends Kedalaman difusi tergantung

on the material properties. ives some numbers for pada sifat materialnya. Tabel 1 g Ives beberapa nomor untuk

different materials. bahan yang berbeda. Since especially for glass and plastics the Karena terutama untuk kaca dan plastik yang

material can be more or less transparent for certain wave- material dapat lebih atau kurang transparan untuk gelombang tertentu

lengths this is just a rough indication. panjang ini hanyalah sebuah indikasi kasar. Detailed information Informasi rinci

is given by Bosman In general we will consider pulses Bosman diberikan oleh [4]. Secara umum kita akan mempertimbangkan pulsa

shorter than 1 ps as ultrashort. lebih pendek dari 1 ps sebagai ultrashort.




Based on physical considerations a removal rate of Berdasarkan pertimbangan fisik tingkat penghapusan

10 nm/pulse at F = 1 J/cm 10 nm / pulsa di F cm = 1 J /

2 2

is expected on steel, while an diharapkan pada baja, sementara

excess of laser fluence is spilled. kelebihan fluence laser tumpah. Experiments at Lawrence Percobaan di Lawrence

Livermore however, show higher yields of 50 nm/pulse at Livermore bagaimanapun, menunjukkan hasil yang lebih tinggi dari 50 nm / denyut nadi di

F = 4 J/cm F = 4 J / cm

2 2

up to 350 nm/pulse at F = 14 J/cm sampai 350 nm / pulsa di F = 14 J / cm

2 2

which is yang

the saturation limit according to Semak These results are batas saturasi sesuai dengan Semak [5]. Hasil ini

explained by the interaction with the hot solid plasma that is dijelaskan oleh interaksi dengan plasma padat panas yang

Table 1 Tabel 1

Ultrashort pulses times for some materials Ultrashort pulsa kali untuk beberapa bahan

Material Materi

Pulse length Pulse panjang

Metals Logam

1 ps 1 ps

Ceramics Keramik

10 ps 10 ps

Plastics Plastik

1 ns 1 ns

Fig. Gambar. 7. 7. Ablation of silicon by a 200 fs, 5 × 10 Ablasi silikon oleh fs 200, 5 × 10


10 10

W/cm W / cm

2 2

laser pulse. pulsa laser. The Para

5 nm thick layer is released from the surface within 3 ps 5 nm lapisan tebal dilepaskan dari permukaan dalam 3 id [7].

formed during the pulse and which is expected to evaporate terbentuk selama pulsa dan yang diharapkan menguap

metal even after the pulse has been finished. logam bahkan setelah pulsa telah selesai. According to Menurut

Semak, there is no detailed knowledge about the real inter- Semak, tidak ada pengetahuan rinci tentang nyata antar-

action processes during femtosecond laser pulses up to now. tindakan proses selama pulsa laser femtosecond sampai sekarang.

Computer simulations however, based on three-dimensional Namun simulasi komputer, berdasarkan tiga dimensi

molecular dynamics, will give some insight in the interac- dinamika molekuler, akan memberikan beberapa wawasan dalam interaksi-

tion phenomena. tion fenomena. Ohmura et al. Ohmura dkk. [6-9] have simulated the memiliki simulasi

interaction and ablation behaviour of aluminium, copper interaksi dan perilaku ablasi dari aluminium, tembaga

and silicon at 266 nm wavelength ( . dan silikon pada panjang gelombang 266 nm ( Gambar 7.) . The optical Optik

penetration depth was 7, 12 and 5 nm, respectively. kedalaman penetrasi adalah 7, 12 dan 5 nm, masing-masing.

The applied power density was in the range of ( 5–50 ) × Kepadatan daya yang digunakan berada dalam kisaran (50-50) ×

10 10

9 9

W/cm W / cm

2 2

. . It was found that the material evaporates as Ditemukan bahwa materi menguap sebagai




small particles (0.3–10 nm), most of them smaller than 1 nm. kecil partikel (0,3-10 nm), kebanyakan dari mereka lebih kecil dari 1 nm.

The average velocity of the particles is several kilometres Kecepatan rata-rata partikel adalah beberapa kilometer

per second or more, but there are also particles whose veloc- per detik atau lebih, tetapi ada juga partikel yang veloc-

ities are in opposite direction. ities berada dalam arah yang berlawanan. They return to the substrate Mereka kembali ke substrat

causing some deposition of debris. menyebabkan beberapa deposisi dari puing-puing. Another effect found by Efek lain yang ditemukan oleh

simulation was the generation of dislocation slip planes and simulasi adalah generasi bidang slip dislokasi dan

vacancies due to shock waves acting until 50 nm below the karena gelombang kejut bertindak sampai 50 nm di bawah lowongan

surface. permukaan.

4.1. 4.1. Generation of short laser pulses Generasi pulsa laser pendek

The mechanism for generating laser pulses lies in the Mekanisme untuk menghasilkan pulsa laser terletak pada

nature of the active laser medium and the corresponding sifat dari media laser yang aktif dan yang sesuai

lifetimes of the atomic energy levels. tahan dari tingkat energi atom. By using different Dengan menggunakan berbagai

pulse generation techniques generasi pulsa teknik [10] the pulse duration, pulse durasi pulsa, pulsa

energy and reproducibility can be modified over wide ranges. energi dan reproduktifitas dapat dimodifikasi atas rentang luas.

• Gain switching . • Keuntungan switching. It can be regarded as the most direct Hal ini dapat dianggap sebagai yang paling langsung

method to generate laser pulses. metode untuk menghasilkan pulsa laser. After the pumping pro- Setelah memompa pro-

cess has been started, the population inversion builds cess telah dimulai, inversi populasi membangun

up. up. The laser starts to oscillate when the critical inversion Laser mulai berosilasi ketika inversi kritis


is reached, ie the gain becomes larger than losses. tercapai, yaitu mendapatkan menjadi lebih besar dari kerugian. This Ini

continues until the pumping process is switched off, or terus sampai proses pemompaan dimatikan, atau

until the losses become higher than the amplification. sampai kerugian menjadi lebih tinggi dari amplifikasi. The Para

reproducibility and stability are stochastic. reproduktifitas dan stabilitas stokastik. Pulse duration Durasi pulsa

available from flash lamp-pumped solid-state lasers by tersedia dari lampu flash-dipompa solid-state laser dengan

gain switching can vary from 10 s to 10 ms. beralih keuntungan dapat bervariasi dari 10 s sampai 10 ms.

• Q-switching . • Q-switching. The output of a gain switched, pulsed solid- Output dari mendapatkan diaktifkan, berdenyut-padat

state laser is generally a train of irregular pulses. negara laser umumnya kereta api pulsa tidak teratur. It is pos- Ini adalah pos-

sible to remove these irregularities and at the same time jawab untuk menghapus penyimpangan dan pada saat yang sama

increase the peak power by Q -switching. meningkatkan daya puncak oleh Q-switching. Such lasers emit Seperti laser memancarkan

one giant pulse per operational cycle. salah satu raksasa pulsa per siklus operasional. The pulse length Panjang pulsa

is less than a microsecond down to several nanoseconds kurang dari satu mikrodetik ke beberapa nanodetik

Page 5 Halaman 5

6 6


Fig. Gambar. 8. Q -switching techniques. 8. Q-switching teknik.

with peak powers between 10 dengan kekuatan puncak antara 10

6 6

and 10 dan 10

9 9

W. This technique W. Teknik ini

can also be applied to continuously pumped lasers in or- juga dapat diterapkan untuk laser terus menerus dipompa dalam atau-

der to produce a train of Q -switched pulses with regular der untuk menghasilkan sebuah kereta Q-switched pulsa dengan teratur

duration, peak power, and repetition rate. durasi, puncak kekuasaan, dan tingkat pengulangan. The energy is Energi yang

stored in the laser material during pumping in the form of disimpan dalam bahan laser selama pemompaan dalam bentuk

excited atoms and then released in a single, short burst. atom gembira dan kemudian dilepaskan dalam ledakan, tunggal pendek.

This is done by changing the optical quality of the laser Hal ini dilakukan dengan mengubah kualitas optik laser

cavity. rongga. The quality factor Q is defined as the ratio of the Faktor Kualitas Q didefinisikan sebagai rasio dari

energy stored in the cavity to the energy loss per cycle. energi yang tersimpan dalam rongga hilangnya energi per siklus.

During pumping the high reflectivity (HR) mirror is ef- Selama memompa reflektifitas tinggi (SDM) cermin ef-

fectively removed from the system preventing laser emis- fectively dihapus dari sistem laser yang mencegah EMIS-

sion and a large amount of energy is stored in the active Sion dan sejumlah besar energi yang tersimpan dalam aktif

medium. menengah. When the HR mirror is returned to proper align- Ketika cermin HR kembali ke tepat menyelaraskan-

ment most of the stored energy emerges in a single short pemerintah sebagian besar energi yang tersimpan muncul dalam pendek tunggal

pulse A Q -switch is essentially a shutter placed be- pulsa [11]. Sebuah T-saklar pada dasarnya adalah sebuah rana ditempatkan menjadi-

tween the active medium and the HR mirror. tween media aktif dan cermin SDM. With this Dengan

shutter closed, the HR mirror is blocked preventing oscil- rana tertutup, cermin HR diblokir mencegah oscil-


lation. lation. When the amplifier gain reaches a predetermined Ketika gain penguat mencapai yang telah ditetapkan

value, the shutter is opened to increase the cavity qual- nilai, rana dibuka untuk meningkatkan rongga qual-

ity. ity. Several techniques can be used for Q -switching lasers Beberapa teknik dapat digunakan untuk Q-switching laser

( ( Gambar. 8).

◦ Spinning reflectors are used quite frequently in Q - ◦ reflektor berputar yang digunakan cukup sering dalam Q -

switched systems where it is not necessary to closely beralih sistem di mana tidak perlu untuk dekat

synchronise the output to some other event. sinkronisasi output ke beberapa acara lainnya. Usually Biasanya

the high reflecting mirror is rotated so that the mirror cermin mencerminkan tinggi adalah diputar sehingga cermin

is tilted out of alignment. dimiringkan keluar dari keselarasan. The system is Q -switched Sistem ini adalah Q-switched

when the mirror rotates back into alignment (it is in ketika cermin berputar kembali ke keselarasan (itu adalah di

alignment once each revolution). keselarasan ketika revolusi masing-masing). Switching time is Waktu switching

typically a few nanoseconds. biasanya beberapa nanodetik.

◦ Electro-optic Q-switching uses a polarisation filter and ◦ Elektro-optik Q-switching menggunakan filter polarisasi dan

rotator placed into the reflecting cavity between the rotator ditempatkan ke dalam rongga mencerminkan antara

laser rod and the reflecting mirror. Laser batang dan cermin yang memantulkan. Rotating the polari- Memutar polarisasi

sation vector of the laser beam inside the cavity results personalisasi vektor dari sinar laser dalam rongga hasil

in low cavity feedback so that it cannot pass through dalam umpan balik rongga rendah sehingga tidak dapat melewati

the polarisation filter. filter polarisasi. When this polarisation rotation is Ketika ini rotasi polarisasi


terminated, the cavity reflectivity is high and the sys- dihentikan, rongga reflektifitas tinggi dan sys-

tem will produce a giant pulse. tem akan menghasilkan pulsa raksasa. Two of the electro-optic Dua dari elektro-optik

devices used in this application are Kerr cells and Pock- perangkat yang digunakan dalam aplikasi ini adalah sel-sel Kerr dan bintik-

els cells. els sel. The Pockels effect is a linear electro-optical Efek Pockels adalah linier elektro-optik

effect, ie the refraction index change in the parallel efek, yaitu perubahan indeks bias di paralel

and orthogonal direction is proportional to the applied dan arah ortogonal sebanding dengan yang diterapkan

voltage. tegangan. The Kerr effect is a non-linear electro-optical Efek Kerr adalah non-linier elektro-optik

effect dependent on a square function of the applied tergantung pada fungsi kuadrat diterapkan efek

voltage. tegangan. Switching time is fast, less than a nanosecond. Waktu switching cepat, kurang dari nanodetik.

◦ Acousto-optic Q-switches have a transparent element ◦ acousto-optik Q-switch memiliki unsur transparan

placed in the cavity. ditempatkan dalam rongga. This element, when excited with Elemen ini, ketika gembira dengan

intense standing acoustic waves by a piezoelectric crys- intens akustik gelombang berdiri oleh piezoelektrik Crys-

tal, exhibits a diffraction effect on the intracavity laser tal, pameran efek difraksi pada laser intrakaviter

beam and diffracts part of the beam out of the cavity balok dan diffracts bagian dari balok keluar dari rongga

alignment. keselarasan. This results in a low feedback. Hal ini menghasilkan umpan balik yang rendah. When the Ketika

acoustic wave is over, the diffraction disappears and the gelombang akustik berakhir, difraksi menghilang dan

system emits a giant pulse. sistem memancarkan pulsa raksasa. Switching time is slow at Waktu switching lambat

100 ns or greater. 100 ns atau yang lebih besar.

◦ Saturable absorbers are available as thin films on glass ◦ peredam saturable tersedia sebagai film tipis pada kaca

substrates or as liquids in glass cells. substrat atau sebagai cairan dalam sel kaca. For Q -switching, Untuk Q-switching,

a dye cell is placed in the laser cavity. sel pewarna ditempatkan dalam rongga laser. The dye absorbs Pewarna menyerap

the laser wavelength presenting a very high cavity loss panjang gelombang laser menyajikan kehilangan rongga yang sangat tinggi

to the laser, and preventing lasing until the amplifier ke penguat laser, dan mencegah sampai penguat

has been pumped to a high gain state. telah dipompa ke negara gain tinggi. When the irradi- Ketika irradi-

ance from the active medium becomes intense enough, Ance dari media aktif menjadi cukup kuat,

the energy that is absorbed by the dye optically pumps energi yang diserap oleh pewarna optik pompa

the dye material, causing it to be transparent at the bahan pewarna, menyebabkan ia menjadi transparan di

laser wavelength. panjang gelombang laser. The dye cell is bleached and causes Sel pewarna dikelantang dan menyebabkan

no longer high cavity losses, ie the quality of the res- tidak lagi kerugian rongga tinggi, yaitu kualitas res-

onator increases. onator meningkat. The absorption change of the dye is Perubahan penyerapan pewarna

the equivalent of Q -switching in the laser, and it can setara Q-switching dalam laser, dan dapat

occur in less than a nanosecond. terjadi dalam waktu kurang dari satu nanodetik. The switching time is Waktu switching

fast. cepat.

• Mode-locking . • Mode-locking. While Q -switching can be used to generate Sementara Q-switching dapat digunakan untuk menghasilkan

pulses with high intensities in the ns-range, mode-locking pulsa dengan intensitas tinggi di ns-jangkauan, modus penguncian-

is used to generate ultrashort laser pulses with pulse du- digunakan untuk menghasilkan laser ultrashort pulsa dengan pulsa du-

ration in the ps- to fs-range. ransum dalam kisaran fs-ps-ke. Pulses in the ps-range were Pulsa di ps jarak yang

generated for the first time by passive mode-locking of dihasilkan untuk pertama kalinya oleh modus-penguncian pasif

a ruby laser shortly after its discovery by Mocker in the ruby laser yang tak lama setelah penemuannya oleh pencemooh di

mid-1960s Mode-locking can be used very effec- pertengahan 1960-an [12]. Mode penguncian dapat digunakan sangat efektivitas

tively for lasers with a relatively broad laser transition tively untuk laser dengan transisi laser yang relatif luas

bandwidth, and thus for lasers with a broad amplification bandwidth, dan dengan demikian untuk laser dengan amplifikasi yang luas

profile, in which numerous longitudinal modes can oscil- profil, di mana mode longitudinal yang banyak dapat oscil-

late simultaneously. akhir secara bersamaan. For achieving the mode-locking con- Untuk mencapai modus-penguncian con-

dition, active and passive mode-locking techniques can be dition, aktif dan pasif mode-penguncian teknik dapat

used. digunakan.

Active mode-locking implies that the resonator is Aktif mode-mengunci menyiratkan bahwa resonator

equipped with a modulator, which is triggered by an exter- dilengkapi dengan modulator, yang dipicu oleh Exter-

nal signal in such a way that a sinusoidal modulation of the nal sinyal sedemikian rupa sehingga modulasi sinusoidal dari

losses in the optical resonator takes place. kerugian dalam resonator optik terjadi. The frequency is Frekuensi

equal to the frequency distance of the longitudinal modes. sama dengan jarak frekuensi modus longitudinal.

Initially, this loss modulation represents an amplitude mod- Awalnya, ini merupakan kerugian modulasi amplitudo mod

ulation with the frequency of the mode, which starts to modulasi dengan frekuensi mode, yang mulai

oscillate first at a maximum amplification at the frequency. berosilasi pertama pada amplifikasi maksimum pada frekuensi.


This modulation then induces the neighbouring modes with Modulasi ini kemudian menginduksi mode tetangga dengan

the frequencies, which experience an amplitude modula- frekuensi, yang mengalami modulasi amplitudo

tion as well. tion juga. This process continues until all longitudinal Proses ini berlanjut sampai semua membujur

modes within the amplification bandwidth of the laser are mode dalam bandwidth amplifikasi laser adalah

coupled and synchronised. digabungkan dan disinkronisasi. Flash lamp-pumped solid-state Lampu flash-dipompa solid-state

lasers typically produce pulse durations of 100 ps, with laser biasanya menghasilkan jangka waktu yang pulsa 100 ps, dengan

Page 6 Halaman 6


7 7

Table 2 Tabel 2

Short pulsed lasers Pendek berdenyut laser

Laser Laser

Wavelength (nm) Panjang gelombang (nm)

Pulse length Pulse panjang

Frequency (kHz) Frekuensi (kHz)

TEA CO TEA CO

2 2

10600 10600

200 s 200 s

5 5

Nd:YAG Nd: YAG

1060, 532, 355, 266 1060, 532, 355, 266

100 ns 10 ns 100 ns 10 ns

50 50

Excimer Excimer

193–351 193-351

20 ns 20 ns

0.1–1 0.1-1

Copper vapor Tembaga uap

611–578 611-578

30 ns 30 ns

4–20 4-20

Ti Sapphire Ti Sapphire

775 775

100 fs 100 fs

1–250 1-250

Nd:YAG and 30 ps with Nd:YLF using active mode-locking. Nd: YAG dan 30 ps dengan Nd: YLF menggunakan modus penguncian-aktif.

Diode-pumped Nd:YLF lasers with active mode-locking Dipompa dioda-Nd: YLF laser dengan mode-penguncian aktif

are even able to provide laser pulses below 10 ps. bahkan mampu memberikan pulsa laser di bawah 10 ps.

Passive mode-locking is based on the same principle as Modus penguncian-pasif didasarkan pada prinsip yang sama seperti

active mode-locking, which is a temporal modulation of the modus penguncian-aktif, yang merupakan modulasi temporal

resonator losses. resonator kerugian. In contrast to active mode-locking, the laser Berbeda dengan modus-penguncian aktif, laser

system itself determines the point in time at which the losses sistem itu sendiri menentukan titik dalam waktu di mana kerugian

are at their minimum berada di minimum mereka [13].

5. 5. Overview of lasers and application fields Sekilas laser dan bidang aplikasi

The passively Q -switched micro-lasers pen new Secara pasif Q-switched laser mikro [14,15] o pena baru



ways for micro-machining. cara untuk mikro-mesin. A continuous wave diode laser Sebuah dioda laser gelombang kontinyu

of about 1 W is used to pump a laser material with a sat- dari sekitar 1 W digunakan untuk memompa bahan laser dengan duduk-

urable absorber on the output window. urable absorber pada jendela output. When this solid-state Saat ini solid-state

Q -switch reaches the threshold it becomes transparent within Q-switch mencapai batas itu menjadi transparan dalam

a nanosecond and a short pulse (0.3–1.5 ns) is delivered. nanodetik dan pulsa pendek (0,3-1,5 ns) yang disampaikan.

Repetition rates are between 2 and 50 kHz. Tingkat pengulangan adalah antara 2 dan 50 kHz. An overview of Ikhtisar

lasers and micro-machining applications is given in laser dan mikro-mesin aplikasi diberikan dalam Tabel 2

dan 3.

Table 3 Tabel 3

Laser micro-machining applications Laser mikro-mesin aplikasi [16]

Laser Laser

Applications Aplikasi

Material Materi

Micro-electronics packaging Mikro-elektronik kemasan

Excimer Excimer

Via drilling and interconnect drilling Via pengeboran dan pengeboran interkoneksi

Plastics, ceramics, silicon Plastik, keramik, silikon

Lamp-pumped solid-state Lampu-dipompa solid-state

Via drilling and interconnect drilling Via pengeboran dan pengeboran interkoneksi

Plastics, metal, ceramics, silicon Plastik, logam, keramik, silikon

Diode-pumped solid-state Dioda-dipompa solid-state

High volume via drilling, tuning quartz oscillators Volume tinggi melalui pengeboran, tuning osilator kuarsa




Plastics, metal, inorganic Plastik, logam, anorganik

CO CO

2 2

sealed or TEA tertutup atau TEH

Excising and scribing of circuit devices, large panel via drilling Excising dan memotong perangkat sirkuit, panel besar melalui pengeboran

Ceramics, plastics Keramik, plastik

Semiconductor manufacturing Manufaktur semikonduktor

Excimer Excimer

UV-lithography IC repair, thin films, wafer cleaning UV-litografi IC perbaikan, film tipis, membersihkan wafer

Resist, plastics, metals, oxides silicon Resist, plastik, logam, oksida silikon

Solid-state Solid-state

IC repair, thin films, bulk machining resistor and capacitor trimming IC perbaikan, film tipis, mesin resistor dan kapasitor massal pemangkasan

Plastics, silicon, metals, oxides Plastik, silikon, logam, oksida

silicon, thick film silikon, film tebal

CO CO

2 2

or TEA atau TEH

Excising, trimming Excising, pemangkasan

Silicon Silicon

Data-storage devices Data-perangkat penyimpanan

Excimer Excimer

Wire stripping air bearings, heads micro via drilling Kawat bantalan udara pengupasan, kepala mikro melalui pengeboran

Plastics, glass silicon ceramics plastics Plastik, kaca silikon keramik plastik

Diode-pumped solid-state Dioda-dipompa solid-state

Disk texturing servo etching micro via drilling Disk texturing servo etsa mikro melalui pengeboran

Metal, ceramics metals, plastic Logam, keramik logam, plastik

CO CO

2 2

or TEA atau TEH

Wire stripping Kawat pengupasan

Plastics Plastik

Medical devices Perangkat medis

Excimer Excimer

Drilling catheters balloons, angioplasty devices. Pengeboran kateter balon, perangkat angioplasti. Micro-orifice drilling Micro-lubang pengeboran

Plastics, metals ceramics, inorganics Plastik, logam keramik, inorganics


Stents, diagnostic tools Stent, alat diagnostik

Metals Logam

CO CO

2 2

or TEA atau TEH

Orifice drilling Lubang pengeboran

Plastics Plastik

Communication and computer peripherals Komunikasi dan peripheral komputer

Excimer Excimer

Cellular phone, fiber gratings, flat panel annealing, ink jet heads Selular telepon, grating serat, panel datar anil, tinta jet kepala

Plastics, silicon, glass, metals, inorganics Plastik, silikon, kaca, logam, inorganics


Via interconnect coating removal tape devices Melalui perangkat interkoneksi penghapusan lapisan pita

Plastics, metals, oxides, ceramics Plastik, logam, oksida, keramik

CO CO

2 2

or TEA atau TEH

Optical circuits Optik sirkuit

Glass, silicon Kaca, silikon

Table 4 Tabel 4

Roadmap for solid-state laser systems for industrial applications Roadmap untuk solid-state sistem laser untuk aplikasi industri

6. 6. Solid-state pulsed lasers Solid-state laser berdenyut

The most important parameters for the laser performance Yang paling penting parameter untuk kinerja laser

are shown in pulse energy E ditunjukkan dalam Tabel 4: pulsa energi E

p p

(mJ), repetition rate (MJ), tingkat pengulangan

v v

rep reputasi

, pulse duration t , Durasi pulsa t

p p

, and beam quality M , Dan balok kualitas M

2 2

. . For the high- Untuk high-

est beam quality ( M est balok kualitas (M

2 2

= 1) beam is diffraction limited. = 1) berkas difraksi terbatas. The Para

key properties are beam quality and output power as well as properti kunci balok kualitas dan daya output serta

compact design. desain kompak. The combination of enhanced capabilities Kombinasi kemampuan ditingkatkan

for tailoring the optical energy density with new laser sys- untuk menjahit kepadatan energi optik dengan laser baru sistem-

tems and improved processing strategies using the advanced U raian dan strategi peningkatan pengolahan menggunakan canggih


picosecond and femtosecond lasers eads to further im- picosecond dan femtosecond laser [17] l EADS untuk lebih im-

provement. provement.

Actual developments enable new applications like mark- Perkembangan aktual memungkinkan aplikasi baru seperti mark-

ing inside transparent materials as well as polishing of metal ing di dalam bahan transparan serta polishing logam

parts ( micro-machining of transparent material with bagian ( Gambar. 10), mikro-mesin material yang transparan dengan

Page 7 Halaman 7

8 8


high form accuracy and also generation of EUV radiation at bentuk tinggi akurasi dan juga generasi radiasi EUV di

13 nm wavelength for next generation lithography. 13 nm panjang gelombang untuk litografi generasi berikutnya. Beyond Luar

metals and ceramics also materials like diamond and semi- logam dan keramik juga bahan seperti berlian dan semi-

conductors as well as very weak materials like silicon and konduktor serta sangat lemah seperti bahan silikon dan

rubber can be processed. karet dapat diproses.

Tailoring the laser performance is balancing the funda- Menjahit kinerja laser yang menyeimbangkan Funda-

mental phenomena involved in the laser action and taking terlibat dalam tindakan laser dan mengambil jiwa fenomena

full advantage of the diode laser as excitation source for penuh keuntungan dari dioda laser sebagai sumber eksitasi untuk

the laser crystal. kristal laser. The mechanisms of excitation, amplifica- Mekanisme eksitasi, amplifica-

tion and saturation in the crystal, depending on spectral and tion dan saturasi dalam kristal, tergantung pada spektral dan



spatial matching of diode pump volume to the volume of spasial pencocokan volume dioda pompa dengan volume

the desired laser mode, influence efficiency and beam qual- mode laser yang diinginkan, efisiensi pengaruh dan balok qual-

ity. ity. In conventional side pumped laser designs for example Di sisi desain konvensional dipompa laser untuk misalnya

thermo-optical effects introduce thermal lensing and bire- termo-optik efek memperkenalkan lensa termal dan bire-

fringence which reduce beam quality and stable laser op- fringence yang mengurangi kualitas balok dan laser stabil op-

eration. timbangkan. As consequence of thermal induced birefringence Sebagai konsekuensi dari birefringence diinduksi termal

the polarisation is changed and optical losses are intro- polarisasi berubah dan kerugian optik intro-

duced. diproduksi. Successful resonator design depends on knowledge Resonator desain yang sukses tergantung pada pengetahuan

about the physical phenomena. tentang fenomena fisik. Currently applied designs Saat ini diterapkan desain

are yang

• Rod end pumped . • Rod akhir dipompa. The output power is limited by thermo Output daya dibatasi oleh termo

mechanical damage of the crystal even for high strength kerusakan mekanik kristal bahkan untuk kekuatan tinggi

YAG-material. Yag-materi. The beam quality and scalability of output Kualitas balok dan skalabilitas output

power is limited by thermal lensing. daya dibatasi oleh lensa termal.

• Rod side pumped . • sisi Rod dipompa. The beam quality is limited by bire- Kualitas balok dibatasi oleh bire-

fringence, since the thermal lens becomes polarisation de- fringence, karena lensa termal menjadi polarisasi de-

pendent. independen. In spite of these limitations actual development Terlepas dari keterbatasan pembangunan yang sebenarnya

of industrial solutions for robust and economical power solusi industri untuk kekuasaan yang kuat dan ekonomis

amplifier for next generation EUV-Lithography are based penguat untuk EUV Litografi-generasi berikutnya didasarkan

on rod side pumped modules. di sisi batang dipompa modul.

• Slab side pumped ( conventional, almost the whole slab • Slab dipompa sisi (konvensional, hampir seluruh lempengan

volume is excited ). volume bersemangat). The amplifier gain is limited by par- Gain amplifier dibatasi oleh par-

asitic modes. asitic mode. The laser emission is not gain guided and Emisi laser tidak mendapatkan dipandu dan

therefore additional, parasitic modes are amplified out- Oleh karena itu tambahan, parasit mode diperkuat keluar-

side the fundamental mode volume. volume sisi modus mendasar. The output power is Daya output

limited by thermo mechanical damage of the crystal. dibatasi oleh kerusakan termo mekanis dari kristal. In Dalam

particular excitation and heating at the corners and edges khususnya eksitasi dan pemanasan pada sudut dan tepi

of the crystal are critical. kristal adalah penting.

• Innoslab end pumped . • Innoslab akhir dipompa. The scalability of the laser power at Skalabilitas dari kekuatan laser pada

high beam quality is limited by the spatial homogeneity of kualitas balok tinggi dibatasi oleh homogenitas spasial

the pump radiation in the scaling direction. pompa radiasi dalam arah skala. Shaping of the Membentuk dari

diode laser beam by optical integrators is the challenge. sinar laser dioda oleh integrator optik adalah tantangan.

• Disc end pumped . • Disc akhir dipompa. The thin (100 m) disc concept The (100 m) disk tipis konsep [18]

relies on multi-pass excitation and high regenerative am- bergantung pada multi-pass eksitasi dan regeneratif yang tinggi am-

plification in order to compensate the small crystal vol- plification dalam rangka untuk mengkompensasi kristal kecil vol-

ume. ume. The optical arrangement of multi-pass excitation is Susunan optik multi-pass eksitasi


crucial for the beam quality. penting bagi kualitas balok. In comparison to the end Dibandingkan dengan akhir

pumped slab laser the heat exchange and reflection of the Laser dipompa lempengan pertukaran panas dan refleksi dari

laser light is at the mounted surface of the disc. sinar laser pada permukaan mount dari disk.

New laser sources like diode-pumped solid-state lasers Laser baru sumber-sumber seperti dioda-dipompa solid-state laser

and diode lasers lead to improved beam quality, effi- dan laser dioda menyebabkan kualitas balok ditingkatkan, efisiensi-

ciency and compactness compared to conventional CO ciency dan kekompakan dibandingkan dengan CO konvensional

2 2

and dan

lamp-pumped lasers. lampu-dipompa laser. In the past 4 years the first generation Dalam 4 tahun terakhir generasi pertama

of diode laser-based new laser sources have been introduced dioda sumber berbasis laser laser baru telah diperkenalkan

into industrial production. ke dalam produksi industri. First prototypes of the second Pertama prototipe kedua

Fig. Gambar. 9. 9. The Innoslab concept takes advantage of gain-guided generation Konsep Innoslab mengambil keuntungan dari keuntungan-dipandu generasi

of laser radiation. radiasi laser. Homogeneous excitation by beam shaping of the diode Homogen eksitasi dengan sinar membentuk dioda

laser is a key feature. laser adalah fitur utama.

generation of diode-pumped solid-state lasers are ready for generasi dioda-dipompa solid-state laser yang siap untuk

use. digunakan. Beside improvements in efficiency and beam quality Selain perbaikan dalam efisiensi dan kualitas balok

these laser sources provide short (ns) and ultrashort (ps and sumber laser ini memberikan ps pendek (ns) dan ultrashort (dan

fs) pulses with very high pulse powers, leading to improved fs) pulsa dengan kekuasaan pulsa sangat tinggi, yang menyebabkan peningkatan

process efficiencies and new fields of laser application. proses efisiensi dan bidang baru dari aplikasi laser.

Disc lasers and end pumped slab lasers allow average Disc laser dan akhirnya dipompa laser memungkinkan rata-rata slab

powers up to the kilowatt regime and beam qualities compa- kekuasaan atas kepada rezim kilowatt dan kualitas balok compa-

rable to a CO rable kepada CO yang

2 2

-laser. -Laser. While disk lasers have been proven to Sementara laser disk yang telah terbukti

provide good CW performance, pulse performance is lim- memberikan kinerja yang baik CW, kinerja pulsa lim-

ited by comparable low pulse energy and low gain, leading ited oleh energi pulsa sebanding rendah dan keuntungan yang rendah, terkemuka

to 100 ns pulses in Q -switched operation. sampai 100 ns pulsa di Q-switched operasi. Mode-locked os- Mode-terkunci os-

cillators generating ps pulses at more than 100 W average cillators menghasilkan pulsa ps di lebih dari 100 W rata-rata

output power have been demonstrated. output daya telah dibuktikan.

Slab lasers provide highest beam quality at kilowatt out- Slab laser memberikan kualitas balok tertinggi pada kilowatt keluar-

put level and the ability of short pulse generation (5–10 ns) menempatkan tingkat dan kemampuan generasi pulsa pendek (ns 5-10)

in Q -switch mode. Q-beralih modus. High gain lead to efficient single pass Gain tinggi menyebabkan single pass yang efisien

amplification for example amplification of a 4 W signal at amplifikasi misalnya amplifikasi sinyal W 4 pada

7 ps pulse duration and 100 MHz repetition rate to about 7 ps pulsa durasi dan 100 MHz tingkat pengulangan sampai sekitar

50 W average power with a single amplifier stage are avail- 50 W rata-rata listrik dengan tahap penguat tunggal memanfaatkan-

able already. sudah mampu.

Based on the end pumped slab laser concept ( Berdasarkan akhirnya dipompa konsep laser slab ( Gambar. the 9) yang



Fraunhofer Institute ILT and the Company EdgeWave have Institut Fraunhofer ILT dan EdgeWave Perusahaan telah

developed an electro-optically Q -switched laser delivering mengembangkan sebuah elektro-optik Q-switched laser memberikan

50 W output power at 45 kHz. 50 W output daya di 45 kHz. The pulse length is about Panjang pulsa adalah tentang

5 ns. 5 ns. The pulse energy reaches 5 mJ at 5 kHz. Energi pulsa mencapai 5 mJ pada 5 kHz. The pulse Pulsa

peak power is 800 kW at almost diffraction limited beam daya puncak adalah 800 kW pada hampir balok difraksi terbatas

quality. kualitas. This high peak power and beam quality is used Kekuatan puncak tinggi dan kualitas balok digunakan

for engraving inside transparent materials ( gener- untuk ukiran di dalam bahan transparan ( Gambar. 10) un-

ating three-dimensional pictures. Ating gambar tiga dimensi. A new application is laser Sebuah aplikasi baru adalah laser

polishing; remelting with CW-lasers and finishing by short polishing; hasil peleburan kembali dengan CW-laser dan finishing dengan singkat

pulse lasers. pulsa laser.

Processing of dielectric materials generally requires ultra- Pengolahan bahan dielektrik biasanya membutuhkan ultra-

violet radiation because of the low absorption of the infrared. ungu radiasi karena penyerapan rendah dari inframerah.

Therefore, excimer lasers and frequency-tripled Nd:YAG Oleh karena itu laser excimer, dan frekuensi-tiga kali lipat Nd: YAG

lasers are used because of their good optical absorption laser digunakan karena penyerapan yang baik optik mereka

and high ablation efficiency. dan efisiensi yang tinggi ablasi. Short pulse lasers, especially Pendek pulsa laser, khususnya

frequency-tripled, diode-pumped Nd:YAG lasers with a high frekuensi-tiga kali lipat, dioda-dipompa Nd: YAG laser dengan tinggi

beam quality offer the possibility to ablate these materials kualitas balok menawarkan kemungkinan untuk mengikis bahan-bahan

with high quality. dengan kualitas tinggi. With a spot size of about 10 m, high Dengan ukuran spot sekitar 10 m, tinggi


fluence (>100 J/cm fluence (> 100 J / cm

2 2

) is achieved, so that the materials are ) Tercapai, sehingga bahan-bahan yang

vapourised with small amounts of molten material. vapourised dengan sejumlah kecil bahan cair. This Ini

technique is applicable for drilling small holes with diame- Teknik ini berlaku untuk pengeboran lubang kecil dengan diame-

ters ≥5 m (aspect ratio up to 60) and cutting of thin ceramic ters ≥ 5 m (aspek rasio hingga 60) dan pemotongan keramik tipis

substrates (thickness 0.5 mm). substrat (ketebalan 0,5 mm). The edges are sharp and the Tepi yang tajam dan

surface roughness can be reduced to R kekasaran permukaan dapat dikurangi untuk R

a sebuah

≤ 0 . 1 m. ≤ 0 1 m.. Low ab- Rendah ab-

lation rates (0.05 g per pulse) are in favour of controlled lation tingkat (0,05 g per pulsa) yang mendukung dikendalikan

Page 8 Halaman 8


9 9

Fig. Gambar. 10. 10. Left: engraving inside transparent material at 400 GW/cm Kiri: ukiran dalam material transparan pada 400 GW / cm

2 2

generates optical breakdown causing visible micro deformations and laser polishing by menghasilkan kerusakan optik menyebabkan deformasi mikro terlihat dan polishing laser dengan

remelting with CW-lasers and finishing by short pulse lasers. hasil peleburan kembali dengan CW-laser dan finishing dengan laser gelombang pendek. Right: surface roughness of WC-embossing tool after laser micro-structuring ( λ = 355 nm, Kanan: kekasaran permukaan WC-alat embossing setelah penataan mikro-laser (λ = 355 nm,

f f

p p

= 5 kHz, E = 5 kHz, E

p p

= 0 . 26 mJ). = 0 26 mJ.).

micro-machining and high precision. mikro-mesin dan presisi tinggi. The achieved removal Penghapusan dicapai

depth per pulse has a maximum at a material specific en- mendalam per pulsa memiliki maksimum pada bahan tertentu en-

ergy density and decreases for higher values. ergy kepadatan dan menurun untuk nilai yang lebih tinggi. The thickness Ketebalan

of the recast layer can be reduced to < 5 m depending on dari lapisan merombak dapat dikurangi menjadi <5 m, tergantung pada

energy per pulse and pulse length. energi per pulsa dan panjang pulsa.

Precise products are produced by 30–50% overlap. Precise produk diproduksi oleh tumpang tindih 30-50%. Out Keluar

of this range the roughness increases steeply As an kisaran ini kekasaran meningkat tajam [19,20]. Sebagai

example, the pyramid made of WC as part of an embossing Misalnya, piramida yang terbuat dari WC sebagai bagian dari suatu embossing

tool has a surface roughness, comparable to EDM ( alat memiliki kekasaran permukaan, sebanding dengan EDM ( Gambar. 10).

The ablation removes around 1 m per step without thermal Ablasi menghilangkan sekitar 1 m per langkah tanpa termal

damage. kerusakan. The adhesion of the removed debris is very weak, Adhesi dari puing-puing dihapus sangat lemah,

the structures are cleaned easily in an ultrasonic bath. struktur dibersihkan dengan mudah dalam penangas ultrasonik.

6.1. 6.1. Examples of applications Contoh aplikasi

6.1.1. 6.1.1. Laser cleaning Laser membersihkan

Pulsed Nd:YAG lasers are also used in the cleaning Berdenyut Nd: YAG laser juga digunakan dalam membersihkan

and recycling area. dan daur ulang daerah. Spur Spur [21] has developed a process for telah mengembangkan suatu proses untuk




de-coating compact disks, made of Ø120 mm × 1 . 2mm de-lapisan kompak disk, terbuat dari Ø120 mm x 1. 2mm

polycarbonate discs coated with 50 nm aluminium and polikarbonat cakram aluminium dilapisi dengan 50 nm dan

10 m varnish. 10 m pernis. The industry is seeking solutions for an Industri ini mencari solusi untuk

economical and efficient recycling process due to the EU ekonomis dan efisien proses daur ulang karena Uni Eropa

waste law for information technology. limbah hukum bagi teknologi informasi. It is estimated that Diperkirakan bahwa

of the 10 billion disks annually 3 billion pieces will be dari 10 miliar per tahun disk 3 miliar bagian akan

collected for recycling. dikumpulkan untuk didaur ulang. The applied laser is a 50 W, 8 ns Laser diterapkan adalah 50 W, 8 ns

Q -switched Nd:YAG laser delivering 2 J pulses, which chip Q-switched Nd: YAG laser pulsa memberikan 2 J, mana chip

the aluminium and varnish, and does not influence the trans- aluminium dan pernis, dan tidak mempengaruhi-trans

parent polycarbonate. orangtua polikarbonat. The removal rate at 50 Hz is 22 cm Tingkat penghapusan pada 50 Hz adalah 22 cm

2 2

/s / S

which results in a de-coating time of 5 s and cost (including

handling and labour) of $ 0.04 per disk. This is in the same

order as the production costs of a new disk! [22] .

Another cleaning application is surface cleaning of sil-

icon wafer by 'laser sparking' which is a gas breakdown

caused by an intense laser pulse focussed in the air above

the wafer surface. It was shown by Lee et al. [23] that an

airborne plasma shock wave above the surface successfully

removes small particles (∼1 m diameter) such as tungsten,

copper and gold from the silicon surface. This contactless



cleaning technique is an efficient, fast and damage-free pro-

cess. cess. It has superior characteristics compared with conven-

tional laser cleaning employing direct interactions between

the laser pulse and the particles. In conventional laser clean-

ing a fourth harmonic Q -switched Nd:YAG laser (266 nm,

10 ns) is directed on the Si substrate. The small tungsten

particles are removed by a rapid thermal expansion of the

particle resulting from the laser absorption. This requires Hal ini membutuhkan

fluencies above 0.65 J/cm

2 2

to overcome the strong adhesion

force for smaller particles. The short wavelength is neces-

sary because of the better absorptivity of W, Cu and Au for

this wavelength. The fluency, however, must be kept below

the threshold fluency of Si damage (0.3 J/cm

2 2

). ). This is not Hal ini tidak

enough for efficient particle removal in the conventional way.

In the new contactless method the striking incoming beam

is focussed 2 mm above the surface at around 10

11 11

W/cm W / cm

2 2

causing an optical breakdown of the air resulting in a shock

wave of several hundreds of megapascals [24,25] d epending

on the distance to the origin. This is well above the adhesion

forces of 1 MPa for 1 m or 3 MPa for 0.1 m tungsten par-

ticles. ticles. Once the bond between the particle and the substrate


surface is broken, the detached particles are accelerated to

high velocity and blown away by the expansion following

the shock wave ( Gambar. 11 ). In this application, the fundamental

1064 nm wavelength of the 10 ns Q -switched Nd:YAG laser

can be applied because there is no direct interaction with

the particles. The cleaned area per shock is around 2 cm

2 2

, ,

which is one order above the conventional technique.

Fig. Gambar. 11. 11. Optical micrographs of the silicon surface, (left) before and (right)

after the laser shock treatment for the removal of a mixture of submicron

W, Cu and Au particles adhered on the surface, Lee et al. [23] .

Page 9 Page 9

10 10

J. Meijer / Journal of Materials Processing Technology 149 (2004) 2–17

Fig. Gambar. 12. 12. Laser fine adjustment of an audio head. Laser heating at L rotates

the head clockwise at R counter-clockwise. A pulse at M, moves the head

downwards and at L + R upwards [27] .

Fig. Gambar. 13. 13. Laser adjustment of reed contacts. The distance between the Jarak antara

metal reeds determines the strength of the magnetic field where the switch

closes.

6.1.2. 6.1.2. Adjustment Pengaturan

Pulsed lasers are applied successfully to adjust micro-

electro mechanical assemblies. This opens new ways to

optimise the design of actuators according to Geiger et al.





[26] . Pulsed Nd:YAG as well as excimer lasers are applied

to adjust (and bend) various materials as stainless steel,

copper alloys or lead frame materials like FeNi42. Hoving

[27] describes the adjustment of audio heads mounted on a

dedicated adjustment frame ( Fig. 12 ). Laser pulses on the in-

dicated positions result in a micrometer accuracy fine adjust-

ment. pemerintah. Another application is the adjustment of reed contacts.

The intensity of the adjustment pulse is based on the mea-

sured magnetic field to open/close the contacts ( Fig. 13 ) . A Sebuah

special requirement for this application is that the laserbeam

has to pass the green glass enclosure of the reed contacts.

Laser adjustment is a flexible alternative for micro-bending

by sparks. Otsu et al. [28] found the latter more advanta-

geous for highly reflecting materials like copper.

7. 7. Excimer lasers Excimer laser

Excimer lasers are a family of pulsed lasers operating in

the ultraviolet by a fast electrical discharge in a high-pressure

mixture of rare gas (krypton, argon or xenon) and a halogen

gas (fluorine or hydrogen chloride). The combination of rare

gas and halogen determines the output wavelength. Typical Khas

pulse energies are a few hundred millijoules to one joule.

Table 5 Tabel 5

Photon energies obtained from different laser sources [29]

Laser Laser

Wavelength (nm) Panjang gelombang (nm)

Photon energy (eV)

XeF XeF

351 351







3.53 3.53

XeCl

308 308

4.03 4.03

KrF

248 248

5.00 5.00

KrCl

222 222

5.50 5.50

ArF

193 193

6.42 6.42

F F

2 2

157 157

7.43 7.43

The average power is in the range of 10 W to 1 kW. The Para

pulse length is typical in the 10–20 ns range resulting in peak

powers of tens of megawatts. These lasers offer a variety of

photon energies ( Table 5 ) . Application areas are: ablation,

lithography, micro-fabrication.

7.1. 7.1. Ablation

Two ablation mechanisms are distinguished: photolytic

and pyrolytic processes. In photolytic processes the photon

energy is directly applied to overcome the chemical bonding

energy of (macro) molecules. In case of polymers they are

broken into smaller often gaseous monomers. The photon Foton


energy of the KrF laser is sufficient for most cases ( Tables 5

and 6 ).

When all laser energy is used to overcome the chemical

binding energy, the ideal case, it is known as “cold ablation”.

In case of metals, however, the laser energy is first absorbed

by electrons, then transferred to heat, which melts and evap-

orates the metal, just like other lasers do. Fig. 14 s hows how

in photolytic processes the molecules are taken away, while

pyrolytic processes melt the material first and evaporates

from the melt surface.

The material removal of organic polymers consists of

three steps. First the UV photons are absorbed in the top

layer of typical 0.2 m thickness, then the long chain

molecules in this layer are broken into parts and finally

they are removed from the processing area in the form of

vapour and small particles. Photons with more than 5.1 eV

will break oxygen molecules in its path. This is demon-

strated by the characteristic ozone smell of a 193 nm ArF

beam passing through air. The threshold fluence for a wide

variety of plastics is about 120 mJ/cm

2 2

. . At low fluence the

walls become tapered from about 2

◦ ◦

at 500 mJ/cm

2 2

to 20 sampai 20

◦ ◦




at 150 mJ/cm

2 2

. . Useful fluences are given in Table 7 .

Table 6 Tabel 6

Chemical bonding energies

Chemical bond Ikatan kimia

Bond energy (eV)

Si–Si, Cl–Cl

1.8–3

C–N, C–C

3–3.5

C–H, O–H

4.5–4.9

C=C

7 7

Page 10 Halaman 10


11 11

Fig. Gambar. 14. 14. Interaction of excimer laser radiation with solids. Right: PVC, photolytic ablation. Left: metal, melt. Middle: Al

2 2

O O

3 3

ceramic, combined photolytic

and pyrolytic process. Lambda Physik [30] .

7.2. 7.2. Lithography Litografi

Lithography is a vital step in micro-electronics. The cost Biaya

of lithography is typical 35–40% of the wafer costs. Cur- Cur-



rently mostly the 248 nm KrF laser is applied in step and re-

peat cameras. Based upon trends over the last 20 years [31]

it is likely that 64 Gb DRAMS with 70 nm features will be

in production in 2010. This requires shorter wavelengths of

193 nm and further 157 nm which requires high performance

deep-UV optical components from materials like BaF

2 2

or atau

CaF CAF

2 2

which have to be developed under an tight time sched-

ule for the introduction of 157 nm that the industry is com-

mitted to achieve [32] .

7.3. 7.3. Laser LIGA

Excimer laser ablation is also used for the fabrication of

micro-electro mechanical systems (MEMS) by the LIGA

process. proses. As an alternative for the expensive X-ray LIGA the

laser LIGA process has been developed for the realisation of

three-dimensional micro-structures [33] . This process pro-

duces nickel structures of several hundred-micrometer thick-

nesses. nesses. By alternating deposition of metal and resin layers

complex multiplayer structures can be obtained by excimer

mask projection ablation [34] .

7.4. 7.4. Micro-fabrication

Micro-parts of almost any geometry can be produced by

mask projection. Drilling holes, however, is the key appli-

cation in micro-fabrication. Excimer lasers offer three sig-

nificant advantages for drilling applications over lasers that





emit in the visible and infrared. First, the short ultraviolet

Table 7 Tabel 7

Ablation thresholds for various materials

Material Materi

Fluency (mJ/cm

2 2

) )

Photo resist

30 30

Polycarbonate Polycarbonate

40 40

Polyimide Polimida

45 45

Silicon nitride Silikon nitrida

195 195

SiO SiO

2 2

350 350

Glass, metal oxide

700–1200

Metals Logam

4000–8000

light can be imaged to a smaller spot size than the longer

wavelengths. panjang gelombang. This is because the minimum feature size is

limited by diffraction, which depends linearly with the wave-

length. panjang. The second advantage is that due to the mechanism

of “photoablation” there is less thermal influence or melting

of the surrounding material. Finally, most materials show a

strong absorption in the ultraviolet region. This means that Ini berarti bahwa

the penetration depth is small and each pulse removes only a

thin layer of material, allowing precise control of the drilling

depth [35] .

In printed circuit board (PCB) fabrication many bridging

holes (via's) are produced to make electrical connections in

multi-layer PCBs. The holes are drilled in dielectric poly-

imide layer until the underlying copper layer is uncovered.

The drilling then stops automatically because of the higher

threshold (one order of magnitude) of copper. The conduct-

ing connection is made by a following chemical deposition

of copper on the via walls. The process has been developed

in 1990 by Bachmann [36] and is used for drilling small

≈10 m holes. For bigger holes of 100 m and above the

cheaper and faster CO

2 2

-lasers are currently used.

7.5. 7.5. Ink jet nozzles

Ink jet printers are widely used because they offer good

quality at low cost, based on a simple design. It consist of an

array of small orifices with precisely defined diameter and

taper, each located on top of a channel with resister heater.

Small bubbles are formed when the ink is heated; ejecting

small (3–80 pl) drops out of the nozzle. Riccardi et al. [37]

describes the fabrication of high-resolution bubble ink jet

nozzles, Fig. 15 . Depending on the design up to 300 holes

have to be drilled simultaneously in a 0 . 5mm×15 mm area.

This is obtained by 5× demagnification of a 400 mJ pulse





Fig. Gambar. 15. 15. Array of ink jet nozzles drilled in 50 m thick polyimide.

Page 11 Page 11

12 12


to 0.6–0.8 J/cm

2 2

fluency. kefasihan. About 300 pulses are applied to

obtain 55 m holes with 27

◦ ◦

taper. lancip. The total drilling time

is about 1 s, using a 300 Hz KrF laser. Recent developments Perkembangan terbaru

will require smaller holes below 25 m diameter.

7.6. 7.6. Others Lainnya

There are a lot of other applications of short pulsed ex-

cimer lasers like marking of eye glasses, medical devices,

aircraft cables and electronic devices, writing of fiber Bragg

gratings for telecom applications, medical applications in

surgery, etc. Two of them will be described in more detail,

ablation of diamond and laser cleaning.

7.7. 7.7. Laser ablation of diamond

Diamond is difficult to machine [38] b ecause it is trans-

parent in a wide wavelength range. At high power densi-

ties, however, the diamond is transited into graphite, which

absorbs the laser power and is removed by ablation subse-

quently. berkala. Diamond machining is currently done by microsec-

ond pulse Nd:YAG and nanosecond pulse excimer lasers

[39] .



Examples of applications are drilling holes in wire draw-

ing dies ( Fig. 16 ) and cutting of knife blades for eye surgery.

Thin layers of graphite or amorphous carbon are found on

the surface after laser machining which requires an extra

polishing operation to remove the graphite. An alternative Alternatif

(new) technique is the use of ultrashort femtosecond lasers.

No evidence of graphite was found [40] because the ther-

mal diffusion depth is only 50 nm. Some processing data is

given in Table 8 .

7.8. 7.8. Excimer laser cleaning

Excimer lasers but also Q -switched Nd:YAG lasers are

applied for surface cleaning, particularly in the electronic

industry. industri. Examples are cleaning of silicon stencils (masks

Fig. Gambar. 16. 16. Diamond wire drawing die. Wire opening 50 m (Diamond Tools

Group).

Table 8 Tabel 8

Laser ablation of diamond

Laser Laser

Q -switched

Nd:YAG

Excimer laser

Femtosecond

laser laser

Wavelength Panjang gelombang

1.06 m

248 nm

248 nm

Pulse length




150 ns

20 ns 20 ns

500 fs

Diffusion depth

30 m 30 m

10 m 10 m

50 nm

Fluence (J/cm

2 2

) )

Removal rates per pulse

0.8 0.8

5 nm 5 nm

5 nm 5 nm

2 2

10nm 10nm

15nm

4 4

20nm 20nm

35nm 35nm

6 6

30nm 30nm

50nm

10 10

0.5 m 0,5 m

45 nm 45 nm

20 20

1.0 m

60 nm 60 nm

50 50

2.5 m 2,5 m

150 150

4.0 m 4,0 m

for e-beam lithography), magnetic head sliders and optical

components. komponen. Particles are preferably removed using a thin

liquid film of water or ethanol allowing low energy densities

for an explosive evaporation of the liquid, which blows away

all particles. Differences in ablation threshold are used to

remove printing residues from chromium plated rotogravure

cylinders. silinder. By scanning the whole surface at a fluency be-

low the ablation threshold for the chromium (≈5 J/cm

2 2

) all

contamination is removed in an environmental friendly way

[41] .

7.9. 7.9. Surface cleaning of art

Impressing results were achieved in the restoration of

paintings by 20 ns KrF excimer laser pulses ( Fig. 17 ) . The Para

ablation depth per pulse is about 1 m. Process monitoring

of the laser induced plasma by real time spectroscopy [42]

allows for precise control of the ablation depth and identifi-

cation of the different layers.

Fig. Gambar. 17. 17. Partial (left) and fully cleaned fine arts, Art-Innovation, NL [43] .

Page 12 Halaman 12






13 13

The market forecast for excimer lasers is more or less

stable. stabil. At the low power segment there is a shift from ex-

cimer lasers toward higher harmonic Nd:YAG lasers (green

532 nm and UV 355 or 266 nm), which become available for

low power micro-machining and for semiconductor materi-

als processing. The UV Nd:YAG lasers operate in the same

wavelength and pulse length domain as the excimer laser.

The average output is one to two orders less, but neverthe-

less the peak power intensity is high (10

7 7

to 10 sampai 10

8 8

W/cm W / cm

2 2

) )

because of the short pulse length and superior beam quality.

Another development are the very high power kilo-

watt excimer lasers, which are developed for simultaneous

drilling for huge amounts of small holes for instance for the

aerospace industry (holes for cooling of engine parts and

for boundary layer suction). One of the research efforts in

this area is the generation of longer pulses [44] . The driv-

ing force is an increased overall system efficiency, lower

stresses on the electrical components and better beam qual-

ity. ity. Longer pulses could also be more efficiently transmitted

in fiber delivery systems [45] .

7.10. Three-dimensional micro-machining



With normal mask projection techniques the homoge-

neous power density distribution will result in an equal abla-

tion over the whole area of the mask. For three-dimensional

structures different sets of mask are used. This gener-

ally results in a stepwise structure. Masuzawa et al. [46]

has developed the Hole Area Modulation method using a

semitransparent mask, consisting of series of small holes

enabling a continuous variable depth just by oscillating the

mask in pre-programmed patterns.

8. 8. Copper vapour lasers

Copper vapour lasers (CVL) belong to the family of

metal vapour lasers, which use mixtures of metal vapour

and rare gases to produce laser light. There are copper

vapour, helium–cadmium and gold vapour lasers. They op-

erate at temperatures of 200–1200

◦ ◦

C to keep the metal in

vapour state. The excitation is by electrical discharges in

the gas mixture. Copper vapour lasers produce green and

yellow light from a mixture of copper vapour and helium

Fig. Gambar. 18. 18. Hundred-micrometer holes for medical filters, middle close up of one hole, right blind hole.

or neon. They are excellent sources of short, high intensity

laser pulses at high repetition rate. The active medium,

copper, is contained in a ceramic tube 1 m length, 25 mm

diameter for 20 W output and up to 3 m ×60 mm for 300 W

and more. dan banyak lagi. The tube is contained in vacuum and heated by

a pulsed discharge to 1450

◦ ◦


C where the copper vaporises.

Laser action results from high-energy electrons and neutral

copper atoms. The neon at a pressure of 20–60 mbar starts

the discharge current when the tube is cold.

Copper vapour lasers are mainly applied to drill, cut and

micro-mill materials with a thickness up to 1.5 mm in metals,

silicon, diamond, ceramics and polymers. Typical applica- Khas applica-

tions are: inkjet nozzle drilling, diesel injector drilling, spin-

neret drilling and cutting, precision machining and writing

Fiber Bragg Gratings. Drilling, cutting and micro-milling

are the common applications for the green light [47] . Among

them simple “holes” are the most popular structures. These Ini

are found in medical flow controllers, micro-electronic con-

tacts and medical filters ( Fig. 18 ) . Holes are also used to

make plastics “breathable”, to calibrate leak testers and to

perforate foils.

The light of copper vapour lasers is more strongly ab-

sorbed in metals than that of IR lasers. This leads to Hal ini menyebabkan

deep holes with a small heat-affected zone. Aspect ratios Aspek rasio

of greater than 40 and surface roughness in the order of

1–2 m are reported by Allen et al. [48] .

In the automotive sector engineers are under consider-

ably regulatory pressure to reduce the emission level of

combustion engines. A major contributor to high emissions

is the fuel injector. The current technique of EDM pro-

duces excellent holes but at low processing speed. Hole Lubang

diameters less than 150 m become increasingly difficult.

Micro-machining by CVL has demonstrated the ability to




produce nozzles with diameters of 50–200 m without dross

on the exit side. The entry side has minimum dross, which

can be removed by light abrasion. Fig. 19 ( left) shows some

50 m holes.

Progress in drug discovery and analysis of the human

genome sequence require the development of micro-tools

and techniques to acquire and process vast amounts of data

looking at the behaviour of many thousands of genes to-

gether. gether. This corresponds with increased speed and automa-

tion in biomedical instrumentation like a pin-based picolitre

dispenser to take thousands of genetic samples for massive

Page 13 Halaman 13

14 14


Fig. Gambar. 19. 19. Left: section of diesel injection nozzle. Right: a micro-reservoir pin with a 15 m wide by 600 m long capillary and a reservoir 100 m wide

and 1000 m long [49] .

parallel testing. The critical component is a tapered pin with

a capillary slot [49] p roduced by CVL ( Fig. 19 , right).

Ink jet nozzles require accurate dimensions and smooth

surface finish to obtain laminar flow of ink and prevent

turbulence. turbulensi. Allen et al. [50] has fabricated ink jet noz-

zles of metal sheet by three different fabrication techniques

(micro-electrodischarge machining, micro-drilling and CVL

machining). He evaluated the characteristics of each tech-

nique while assessing the differences between them.

Micro-EDM is one of the few techniques that can be used






for micro-hole fabrication following Almond et al. [51] and dan

Masuzawa [52] . A single hole of 50 m diameter through

100 m thick stainless steel takes typical 3 min. With CVL

a single pulse will remove the material to a depth of 10 m,

which means that micro-holes are machined within seconds

by 30 ns pulses at 10 kHz. The short pulsewidth in CVL

reduces the heat-affected zone. Aspect ratios greater than 40

are reported for stainless steel, the surface roughness is of

the order of 1–2 m. Trepanning was used to improve the

quality of the holes. Results are given in Table 9 .

Although micro-EDM is an established process with ex-

cellent hole quality, its relative slowness is its main draw-

back. kembali. CVL is much faster but the improvement of surface

profile requires further investigation for direct writing of

complex micro-structures as applied in creating channels in

glass plates to control micro-fluid flow, engraving hard ma-

terials, micro-marking for security purposes etc. High preci-

sion micro-machining will be the key application that finally

will cause the industrial breakthrough.

Table 9 Tabel 9

Comparison of micro-hole fabrication methods

Process Proses

Advantages Keuntungan

Disadvantages Kekurangan

Micro-EDM

Surface finish, edge

profile profil

Slow Lambat




CVL CVL

Edge profile, fast

Flaked recast gives rougher

appearance penampilan

Micro-drilling

Fast Cepat

Burring of edges, tool

breakage

9. 9. Femtosecond lasers

The latest generation pulsed lasers delivering the shortest

pulses are the femtosecond lasers. In these systems, puls-

ing is mostly achieved by mode coupling of a broadband

laser source. Typically, the bandwidth exceeds several tens

of nanometer bandwidth, which allows pulse duration well

below 100 fs. Due to the short pulse duration, peak powers

of more than 15 GW can be reached, which gives access to

further ablation mechanisms, like multi-photon ionisation.

Due to the short interaction time, only the electrons within

the material are heated during the pulse duration. Once the Setelah

laser pulse has stopped, the lattice of the material experi-

ences the influence of the overheated electrons. This results Ini hasil

in two different ablation regimes, dependent on the pene-

tration depth of the overheated electrons, which at fluencies

over 500 mJ/cm

2 2

can exceed the optical penetration depth of

about 10 nm [53] . This enables ablation rates up to 250 nm

at 10 J/cm


2 2

. . Especially for low fluences, where the thermal

diffusion length is smaller than the optical penetration depth,

heat diffusion is be strongly suppressed, which allows high-

est precision and minimal heat influence within the material.

The intensity during such laser pulses initiates multi-photon

effects, which allows machining of literally any solid mate-

rial. Rial. Applications are limited to micro-machining processes,

where the total volume of ablated material is rather small

due to the limited average power output.

Most femtosecond lasers are based on titanium:sapphire,

due to its broad bandwidth. The short pulses are generated

within the oscillator, typically providing a pulse train of short

pulses at low pulse energy of some nanojoules per pulse.

As this energy is not sufficient for most micro-machining

applications, further amplification has to be provided. A Sebuah

direct amplification is not viable, as the intensity would

destruct beam profiles and the internal optics. Therefore, Oleh karena itu,

the intensity has to be reduced to sufficient values, which

is being done using the Chirped Pulse Amplification (CPA)

technique [54] . Typical commercial available systems show

average output powers of 1.5 W and up to 250 kHz repetition

Page 14 Page 14


15 15

Fig. Gambar. 20. 20. Prototypes of stents made of: (a) bio-resorbable polymer and (b)

tantalum.


rate. tingkat. This power output allows micro-machining processes,

but limits the amount of removed material per time. Nev- Nev-

ertheless, promising applications are found in the precise

machining of thermal sensitive materials.

Apart from direct use of fs-lasers in medicine for surgery,

for example the correction of myopia like laser assisted

in situ keratomileusis (LASIK), the structuring of medi-

cal implants, eg coronary stents, is a promising applica-

tion with growing industrial interest [55] . Coronary stents

are used as a minimally invasive treatment of arteriosclero-

sis, an alternative for bypass operations. The requirements Persyaratan

of medical implants (eg burr-freeness, X-ray opacity) are

very strict so just a few materials are commonly used. Typ- Typ-

ical materials used for stents are stainless steel or shape

memory alloys. Chemical post-processing techniques have

been developed to achieve the required properties. How- Bagaimana-

ever, these materials are not optimal in several medical as-

pects (eg risk of restenosis, limited bio-compatibility, etc.).

New approaches favour stents for temporary use, which ne-

cessitate bioresorbable materials like special bio-polymers

( Fig. 20a ).

Other materials, like tantalum, show improved X-ray

visibility ( Gambar. 20b ) . For these materials, no established

post-processing technique is available. Most of them show

strong reactions to thermal load. It is essential to avoid in-

fluences on the remaining material in order to keep the spe-

cific material properties. Femtosecond pulse laser material

processing meets these requirements.





9.1. 9.1. Cutting of silicon

Silicon is the most important material in the micro- and

semiconductor industry for the fabrication of micro-chips,

sensors, and actuators. Conventional lasers have not be ap-

plied for high precision structuring of semiconductors as

they cause thermal melting, cracks, and deposits but fem-

tosecond laser systems overcome these limitations, since

thermal and mechanical influences are minimised. Cutting Pemotongan

of silicon using fs-laser pulses shows high quality ( Gambar. 21 )

well suited for cutting thin wafers. In contrast to the conven-

tional dicing method, non-linear narrow cuts are performed

with a wear-free tool. The process quality is enhanced be-

cause there is no interaction between the expanding plasma

and the laser pulse (plasma shielding effect) as light absorp-

tion and ablation are separated in time.

Fig. Gambar. 21. 21. Examples of silicon cutting.

Although femtosecond lasers offer new and very promis-

ing ways of micro-machining almost any solid material, they

are not yet introduced into industrial service due to some

drawbacks. kelemahan. As the CPA-technique is fairly complex, the sys-

tem contains much more optical components than conven-

tional lasers. This might influence the stability of operation

by environmental conditions like temperature, vibrations,

etc. Up to today, those systems are mainly applied for sci-

entific purposes, which necessitates operating the laser by

highly trained staff. For industrial operation, such operators

are not available. tidak tersedia. Therefore, industrial service requires much

easier operations and less maintenance. The laser manufac-



turers have identified these problems, so the fs-lasers are

presently designed to match the requirements of industrial

service. layanan. fs-Lasers will be used for high quality applications,

which are not achievable by other means. Due to high in-

vestments, low-cost applications seem not to be economi-

cally by this kind of lasers. Future laser development will

increase the process speed by increasing repetition rate as

well as average output power. By reducing the costs for the

laser system as well, economical machining of several ap-

plications will be realised.

10. 10. Accuracy Ketepatan

Improvement of accuracy has been a central topic along 50

years of CIRP history as described by Peters et al. [56] , Mer-

chant [57] , McKeown [58] and many others. dan banyak lainnya. Short pulses

have great potential to obtain higher accuracies in dimen-

sional control because of the very small amounts of mate-

rial that can be removed per pulse, as well because the very

small damaged (heat-affected) zone at the surface. Another Lain

merit of using 'image tools' compared with solid tools (eg

EDM) is the wide space, available for release of debris. Ap- Ap-

plications are found in the semiconductor industry where the

demand for accuracy follows from the continuing miniatur-

isation in accordance with Moore's law developed in 1965

[59–61] and in the ultra precision machining following the

trend given by Taniguchi in 1983 [62] .

In 1965, Gordon Moore, the founder of Fairchild Semi-

conductor and Intel, observed only 6 years after the in-

troduction of the commercial planar transistor in 1959






an astounding trend; the number of transistors per chip

was doubling every year. In 1975 Moore updated his law

Page 15 Halaman 15

16 16


distinguishing three contributing components: (1) increas-

ing chip area (15% each year), (2) decreasing feature size

(11% per year, or 27% less area). Both factors resulted in

60% increase of the number transistors per chip; (3) the rest

of the improvement was because of better design. In the first Pada bagian pertama

15 years the chip complexity doubled each year and since

1975 when the design has reached its optimum, the increase

was still 60% per year. When we extrapolate current trends

to the year 2010, the minimum feature size will be 70 nm.

This sets the requirements for the future lasers. The feature Fitur

size depends on four factors; the beam quality should be

excellent ( M

2 2

≈ 1), the wavelength as short as possible in

the UV, the f number small ( f # ≈ 1) and the power density

just above the threshold intensity so that only the central part

of the beam is used. Currently, feature sizes of 30 nm have

been experimentally demonstrated [63] , but it is far from

production. produksi. Companies are assessing nano photolithography

with excimer wavelengths of 193 and 152 nm.

In the machine industry, Taniguchi published his famous

paper in 1983 [62] . From his graphs an increasing accuracy



of 10% per year is found, which is remarkable in balance

with the 11% predicted by Moore. Taniguchi expected in

2010 an ultimate accuracy of 1 nm by atom, molecule or ion

beam machining. He did not consider laserbeam processing

although photons are a much finer tool than atoms or ions.

Even electron beams are not considered because he says:

“it became clear that direct thermal machining using high

energy electron beams is not suitable for ultra precision

machining because the high energy electrons penetrate

the surface layers to depths of many microns or tens of

microns (at 50 kV typically 10 m in aluminium). The Para

energy is transferred to the atoms in the form of heat over

a relatively large zone of several microns”.

The reason that photons can perform better is because:

• photons are much smaller than electrons,

• they are electrical neutral so there are no repulsive forces,

• the optical penetration depth is only 10 nm for metals,

• the thermal penetration depth is of the same order.

Taniguchi could not consider this because there was

no idea of femtosecond machining at that time. Never- Jangan-

theless, some problems have to be solved before laser

micro-machining will be applied on industrial scale. Not Tidak

only the lasers should be more compact and robust but also

the reliability in process- and dimensional control is most

challenging. menantang.

Acknowledgements Ucapan Terima Kasih

Parts of this paper have been derived from the CIRP

keynote paper [10] : K. Du (EdgeWave GmbH, Aachen), A.


Gillner (Fraunhofer Institut für Lasertechnik ILT, Aachen),

D. Hoffmann (Fraunhofer Institut für Lasertechnik ILT,

Aachen), VS Kovalenko (National University of Ukraine,

Kiev), T. Masuzawa (University of Tokyo), A. Ostendorf

(Laser Zentrum Hannover), R. Poprawe (Fraunhofer Insti-

tut für Lasertechnik ILT, Aachen), W. Schulz (Fraunhofer

Institut für Lasertechnik ILT, Aachen).

References Referensi

[1] S. Postma, J. Meijer, RGKM Aarts, Method and device for mea-

suring and controlling a laser welding process, International Patent

WO 03/022508 A1 (2003).

[2] GN Levy, R. Schindell, JP Kruth, Rapid manufacturing and rapid

tooling with layer manufacturing technologies, state of the art and

future perspectives, Ann. CIRP 52 (2) (2003) 589–610.

[3] X. Chen, X. Liu, Short pulsed laser machining: how short is short

enough? cukup? J. Laser Appl. 11 (6) (1999) 268–272.

[4] J. Bosman, Laser engraving processes, Ph.D. Thesis, University of

Twente, in preparation.

[5] V. Semak, Laser drilling: from milli to femto, Laser solutions course,

in: Proceedings of the ICALEO 2001, Jacksonville, October 18,

2001, pp. 1–9.

[6] E. Ohmura, I. Miyamoto, Molecular dynamics simulation on laser

ablation of metals and silicon, Int. J. Jpn. J. JPN. Soc. Soc. Precis. Eng. Eng. 34 (4)

(1998) 248–253.

[7] Y. Ishizaka, K. Watanabe, I. Fukumoto, E. Ohmura, I. Miyamoto,

Three-dimensional molecular dynamics simulation on laser materi-

als processing of silicon, in: Proceedings of the ICALEO98, 1998,

pp. A55–A63.

[8] E. Ohmura, I. Fukumoto, I. Miyamoto, Molecular dynamics simula-

tion on laser ablation and thermal shock phenomena, in: Proceedings

of the ICALEO 1998, pp. A45–A54.

[9] E. Ohmura, I. Fukumoto, Study on fusing- and evaporating process

of fcc metal due to laser irradiation using molecular dynamics, Int.

J. Jpn. J. JPN. Soc. Soc. Precis. Eng. Eng. 30 (1) (1996) 47–48.

[10] J. Meijer, K. Du, A. Gillner, D. Hoffmann, VS Kovalenko, T.

Matsunawa, A. Ostendorf, R. Poprawe, W. Schulz, Laser machining

by short and ultrashort pulses, state of the art and new opportunities

in the age of the photons, Ann. CIRP 51 (2) (2002) 531–550.

[11] FJ McClung, RW Hellwarth, Characteristics of giant optical pul-

sations from ruby, Proc. IEEE 51 (1963) 46.

[12] HW Mocker, RJ Collins, Mode competition and self-locking effects

in a Q -switched ruby laser, Appl. Phys. Phys. Lett. Lett. (7) (1965) 270.

[13] F. Krausz, T. Brabec, C. Spielmann, Self-starting passive mode lock-

ing, Opt. Lett. Lett. 16 (1991) 235.

[14] D. Guillot, Microlasers, Photonics Spectra 32 (1998) 143–146.

[15] VS Kovalenko, Laser Technology, Vyscha Schola, Kiev, 1989, 280

pp. hlm

[16] G. Ogura, J. Angell, D. Wall, Applications test potential of laser

micromachining, Laser Focus World 34 (1998) 117–123.

[17] SM Klimentov, SV Garnov, TV Kononenko, VI Konov, PA

Pivovarov, F. Dausinger, High rate deep channel ablative formation

by picosecond–nanosecond combined laser pulses, Appl. Phys. Phys. A 69

(1999) 633–636.

[18] C. Stewen, K. Contag, M. Larionov, A. Giesen, H. Hügel, A 1 kW

thin disc laser, IEEE JSTQE 6 (4) (2000) 650–658.

[19] HK Tönshoff, J. Mommsen, Process of generating three-dimensional

microstructures with excimer lasers, in: Proceedings of the ECLAT92,

Göttingen, 1992.

[20] D. Hellrung, A. Gillner, R. Poprawe, Laser beam removal of

micro-structures with Nd:YAG lasers, in: Proceedings of the Lasers in

Material Processing Laser'97, Munich, SPIE 3097 (1997) 267–273.

[21] G. Spur, Industrial cleaning technologies for hard surfaces: dry ice

blasting and laser, in: Proceedings of the 40th International deter-

gency Conference IDC'01, 2001, pp. 156–165.

[22] W. Hoving, Philips, CFT, Private communication.

Page 16 Halaman 16


17 17

[23] JM Lee, KG Watkins, WM Steen, Surface cleaning of silicon

wafer by laser sparking, J. Laser Appl. 13 (4) (2001) 154–158.

[24] JF Ready, Effects of High Power Laser Radiation, Academic Press,

New York, 1971, p. 213. 213.

[25] RE Kidder, Nucl. Fusion 8 (1968) 3.

[26] M. Geiger, M. Kleiner, R. Eckstein, N. Tiesler, U. Engel, Micro-

forming, Ann. CIRP 50 (2) (2001) 445–462.

[27] W. Hoving, Laser fine adjustment, in: Proceedings of the ICALEO,

2001. 2001.

[28] M. Otsu, T. Wada, K. Osakada, Micro bending of thin spring by

laser forming and spark forming, Ann. CIRP 50 (1) (2001) 141–144.

[29] J. Meijer, in: JA McGeough (Ed.), Micromachining Materials, Mar-

cel Dekker, 2002, pp. 203–237.

[30] D. Basting, Excimer Laser Technology: Laser Sources, Optics, Sys-

tems and Applications, Lambda Physik AG, Göttingen (D), 2001.

[31] A. Hind, Spectrophotometry takes measure of deep UV lithography,

Photonics Spectra 35 (2001) 82–86.

[32] JH Burnett, ZH Levine, EL Shirley, Hidden in plain sight: can

lithographers design out the intrinsic birefringence of calcium fluo-

ride, or must they find a new material solution for 157 nm lithogra-

phy, Photonics Spectra 35 (2001) 88–92.

[33] http://www.cee.hw.ac.uk/microengineering/microsystems/uv-liga/ . .

[34] JA MacGeough, MC Leu, KP Rajurkar, AKM De Silva, Q.

Liu, Electroforming process and application to micro/macro manu-

facturing, CIRP Ann. 50 (2) (2001) 499–514.

[35] JF Ready, LIA Handbook of Laser Materials Processing, Magnolia

Publ. Publ. Inc., 2001, p. 491. 491.

[36] FG Bachmann, Industrial laser applications, Appl. Surf. Surf. Sci. Sci. 46 46

(1990) 254–263.

[37] G. Riccardi, M. Cantello, F. Mariotti, P. Giacosa, Micromachining

with excimer laser, Ann. CIRP 47 (1) (1998) 145–148.

[38] Lasers are diamond's best friend, Photonics Spectra 26 (1992)

40. 40.

[39] R. Windholz, P. Molian, Nanosecond pulsed excimer laser machining

of CVD diamond and HOPG graphite, J. Mater. Sci. Sci. 32 (1997)

4295–4301.

[40] MD Shirk, PA Molian, Ultrashort laser ablation of diamond, J.

Laser Appl. 10 (2) (1998) 64–70.

[41] R. Lotze, J. Birkel, K. Wissenbach, Entlacken mit Laserstrahlung,

Neue industrielle Anwendungen, JOT Journal für Oberflächentechnik,

1999/8.

[42] S. Klein, T. Stratoudaki, V. Zafiropoulos, J. Hildenhagen, K. Dick-

mann, Th. Lehmkuhl, Laser induced breakdown spectroscopy for on

http://translate.googleusercontent.com/translate_c?hl=id&prev=/search%3Fq%3Dlaser%2Bbeam%2Bmachining%26start%3D10%26hl%3Did%26sa%3DN%26biw%3D1360%26bih%3D637%26prmd%3Dimvnsb&rurl=translate.google.co.id&sl=en&u=http://www.cee.hw.ac.uk/microengineering/microsystems/uv-liga/&usg=ALkJrhhYvY-5FwyQiTRxrxt-pR-nXdq-JA

line laser cleaning of sandstone and stained glasses, Appl. Phys. Phys. A Sebuah

69 (1999) 441–444.

[43] http://www.art-innovation.nl .

[44] A. Schoonderbeek, CA Biesheuvel, RM Hofstra, K.-J. Boller, J.

Meijer, High speed drilling of metals with a long pulse XeCl excimer

laser, Proc. SPIE 4760 (2002).

[45] C. Fotakis, in: Handbook of the EuroLaser Academy, vol. 1, Chapman

& Hall, London, 1998, pp. 227–265.

[46] T. Masuzawa, J. Olde Benneker, JJC Eindhoven, A new method

for three dimensional excimer laser micromachining by hole area

modulation (HAM), Ann. CIRP 49 (2000) 139–142.

[47] V. Kovalenko, M. Anyakin, Y. Uno, Modeling and optimization of

laser semi conductor cutting, in: Proceedings of the ICALEO, Laser

Microfabrication, vol. 90, 2000, pp. 82–92.

[48] D. Allen, H. Almond, P. Logan, A technical comparison of

micro-electrodischarge machining, micro drilling and copper vapour

laser machining for the fabrication of ink jet nozzles, Proc. SPIE SPIE

4019 (2000) 531–540.

[49] S. Elmes, et al., Laser machining of micro reservoir pins for

gene analysis and high throughput screening, in: Proceedings of

the ICALEO Laser Micro Fabrication Conference M303, 2001.

ISBN0912035-73-0.

[50] DM Allen, HJA Almond, JS Bhogal, AA Green, P. Logan, XX

Huang, Typical metrology of micro hole arrays made in stainless

steel foils by two stage EDM, Ann. CIRP 48 (1) (1999) 127–130.

[51] H. Almond, J. Bhogal, DM Allen, A positional accuracy study of

a micro EDM machine, Proc. SPIE 3680 (1999) 1113–1124.

[52] T. Masuzawa, State of the art of micromachining, Ann. CIRP 49 (2)

http://translate.googleusercontent.com/translate_c?hl=id&prev=/search%3Fq%3Dlaser%2Bbeam%2Bmachining%26start%3D10%26hl%3Did%26sa%3DN%26biw%3D1360%26bih%3D637%26prmd%3Dimvnsb&rurl=translate.google.co.id&sl=en&u=http://www.art-innovation.nl/&usg=ALkJrhilPJ8yRe8r_Po537JILAqT1jQ8Lw

(2000) 473–488.

[53] S. Nolte, et al., Ablation of metals by ultrashort laser pulses, J. Opt.

Soc. Soc. Am. Am. B 14 (10) (1997) 2716–2722.

[54] D. Strickland, G. Mourou, Compression of amplified chirped optical

pulses, Opt. Commun. Commun. 56 (1985) 219.

[55] C. Momma, U. Knoop, S. Nolte, Laser cutting of slotted tube coro-

nary stents, State of the art and future developments, Biomed. Res. Res.

(1999) 39–44.

[56] J. Peters, et al., Contribution of CIRP to the metrology and surface

quality evaluation during the last fifty years, Ann. CIRP 50 (2)

(2001) 471–489.

[57] ME Merchant, Delphi forecast of future production engineering,

Ann. Ann. CIRP 20 (2) (1971) 205–213.

[58] PA McKeown, The role of precision engineering in manufacturing

of the future, Ann. CIRP 36 (2) (1987) 495–502.

[59] GE Moore, Cramming more components onto integrated circuits,

Electronics 38 (1965) 114–117.

[60] GE Moore, Progress digital integrated electronics, IEDM Techn.

Digest, Washington (1975) 11–13.

[61] The national Technology Roadmap for Semiconductors, 1994, Semi-

conductor Industry Association, San Jose, California.

[62] N. Taniguchi, Current status in, and future trends of, ultra precision

machining and ultra fine materials processing, Ann. CIRP 32 (2)

(1983) 573–580.

[63] J. Corbett, PA McKeown, GN Peggs, R. Whatmore, Nanotechnol-

ogy: international developments and emerging products, Ann. CIRP

49 (2) (2000) 523–545.

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