European Southern Observatory - TUM Physikdepartment ...

Large format science detectors and

high speed sub-electron noise sensors

for groundbased astronomy

Gert Finger, Domingo Alvarez, Derek Ives, Mark Downing, Olaf

Iwert, Leander Mehrgan, Manfred Meyer, Javier Reyes, Joerg

Stegmeier

European Southern Observatory

VLT on Cerro Paranal

• VLT is ESO

observatory on

Paranal in the

Atacama

dessert in Chile

• four 8 meter

telescopes each

having 3 foci

• four auxiliary

telescopes

• interferometer

CONICA CRIRESS

SINFONI FINITOVISIR

VINCI

VISTA

PRIMA

UVES NACO GIRAFFE

X-SHOOTER FORS

VIMOS OmegaCAM

EMMI

Instruments for VLT

controllers: IRACE: infrared FIERA: optical

Instruments for VLT

GRAVITY

SPHEREMUSE

Visible

AQUARIUS

MID-IR

NIR SAPHIRA

NIR WFS

MATISSE

MID-IR

NIR

VISIR

Visible

NIR

Visible WFS

GALACSI / GRAAL

AO

NGC

both IR and optical

• New General Detector Controller NGC used for all VLT and ELT

instruments

• NGC controller is platform: adaptable and modular design - like lego building blocks

with this?

1% volume

1% power

• ASIC needed for space, development cost is 2 -3 M€

• NGC is more flexible and has better performance than SIDECAR ASIC

because of newer components and no power constraints

NGC –New General detector controller

Backplane

FEB-4Ch

2MHz Module

AQ-32Ch

10MHz

Module

Transition

Module

Replace this

testing lc=2.5 mm 2Kx2K MBE

Hawaii-2RG arrays

Hawaii-2RG 2Kx2K HgCdTe array

• 32 channel package

• cryogenic opamps

• format 2Kx2K

• λc=2.5µm and 5.2 µm

• pixel size 18 µm

• reference pixels

• guide mode

• use cryogenic preamps

instead of ASIC

Hawaii-2RG arrays: workhorse for VLT

• work horse for the VLT at ESO

• 1 Hawaii2RG for SPIFFI

• 4 Hawaii2RG for HAWKI

• 1 Hawaii2RG for X-SHOOTER

• 1 Hawaii2RG for IRDIS in SPHERE

• 1 Hawaii2RG for IFS in SPHERE

• 1 Hawaii2RG for GRAVITY spectrometer

• 1 Hawaii2RG for GRAVITY acq. camera

• 1 Hawaii2RG for MATISSE

• 3 Hawaii2RG for CRIRES mosaic

• 1 Hawaii2RG for CRIRES slit viewer

• 1 Hawaii2RG for ERIS

• 1 Hawaii4RG bare multiplexer

• 4 Hawaii4RG for MOONS

QE comparison of KMOS science arrays

• KMOS is multiobject Integral

Field Spectrograph (IFS)

• three spectrometers fed by

8 pickoff arms with IFUs

• each spectrometer equipped with

one Hawaii-2RG

• QE of 3 KMOS science arrays:

Integral field unit IFU24 cryogenic pickoff arms

Dark current versus temperature

• H2RG λc=2.5μm array

(KMOS)

• generation-recombination

limited above 110K

• Idark exp(-Teff/T)

• surface leakage and

tunneling below 100K

• T=80 K is sufficient for

dark current,

but cosmetics improves

below 80K

• H2RG λc=5μm array

(CRIRES+) has dark

current of 6E-2 e/s/pixel

at 500mV bias

Noise of KMOS arrays for single DCS

• best noise for double correlated

sampling is 6.9 erms

• below 10 erms for all KMOS arrays

Readout noise with Fowler sampling

• increase number of

nondestructive

readouts to reduce

readout noise

• noise 2.8 erms with

64 Fowler pairs

Supernova emission

He I at λ=1083nm taken with IFU

K band: thermal

emission

OH emission lines

from the night sky

XSHOOTER spectrum of SN1987A

courtesy Jason Spyromilio

• cross dispersed echelle spectrograph

• wavelength range: 300 nm to 2.5 μm

• spectral resolution R ~10000

emission from the night sky.

It is very bright

continuum emission from a star

line emission from

the supernova

zoom in to the bottom of the frame

(J-band)



zero counts

sky-sky=0

1 photon every 20 seconds

most of the science contained

in weak signals

we work to get this clean

subtract sky from source



Persistence of Hawaii-2RG in XSHOOTER

• DIT=1.65s ThAr lamp on

• first dark exposure with DIT=128s after 2048s exposure with open slit

Persistence of Hawaii-2RG in XSHOOTER

Persistence of Hawaii-2RG in SINFONI and KMOS

• KMOS #211 and #212

from same lot but

#212 has 6 times higher

persistence

• KMOS #211 and #184 from

different lots but similar

persistence

• persistence device specific

• persistence has to be measured

also optically

• measurments at Teledyne are

not showing persistence as

measured in instrument

2004

2010

Hawaii-2RG mosaic Package

• larger format

with mosaics

• 2x2 mosaic

installed in

HAWK-I

• will also fly on

JWST

OmegaCAM

• Mosaic of 8x4

2Kx4K CCDs

in OmegaCAM

Espresso 9Kx9K CCD

• 9Kx9K e2v CCD

• 10µm pixels

• size 92.4 mm^2

• noise 3 erms

• radial velocity 10 cm/s

• needs thermal stability at

mK level

• λc=28 μm 1Kx1K Si:As BIB array

•VISIR upgrade

•1024 x 1024 pixels

• 64 outputs, from two sides

• Read from centre up and down

Readout

directions

• ESO mounting is in Aladdin-III package

• 124 pin LCC – PCB mounted socket

Manganin weave

development

mid-IR AQUARIUS array for VISISR upgrade

Difference of sums – low frequency noiseSum of differences – high frequency noise

Visual Evidence : 2000 frame data sequence, chopped at low and

high frequencies

Excess Low Frequency Noise (ELFN)

Old DRS detector at 0.25 Hz

AQUARIUS at 5 Hz – NEW

OPERATIONAL DEFAULT

instrument sensitivity as a function of

telescope chop frequency

• new wafer run with thin blocking layer

optimized for high flux of

ground based astronomy

Adaptive Optics (AO)

- removing the twinkle of the stars

Wavefronts from astronomical

objects are distorted by the Earth’s

atmosphere, reducing the spatial

resolution of large telescopes to

that of a 10 cm telescope

1

Wavefront Sensor

measures deviation of

wavefront from a flat

(undistorted) wave

2Control System

computes

commands for the

deformable mirror(s)

3

Deformable mirror

compensates the

distorted wavefront,

achieving diffraction-

limited resolution 4

OFF

ON

AO: open and closed loop

• Multi-Application Curvature

Adaptive Optics MACAO

• used in CRIRES, SPIFFI,

SINFONI

• control loop off /on

• Strehl ratio :

measured peak intensity

compared to diffraction limited

intensity: 60%

WFS for VLT: low noise high speed

add gain in the serial register

Rf1 Rf2 Rf3

If1

If2

If3

Rf2HV

• Achieves lower read noise by adding electron multiplication register before the amplifier.

Electron

Multiplication

Register

e2v L3Vision:

• CCD220 240x240 24 µm pixel

• << 1 e- RON at 16 Mpix/sec

• 1,200 fps with 8 outputs.

e2v CCD220 for GALACSI and GRAAL

e2v CCD220 in AOWFS camera• deployed in SPHERE

• 14 cameras delivered to

GALACSI and GRAAL

• Will be deployed in ERIS and MAORY

•noise of λc=2.5 μm NIR CMOS sensors scaled to

speed of 5 MHz: RON ~ 70 erms (PICNIC,H2RG)

how to achieve noise of <<3 erms at 5 MHz in NIR?

•APD:

•me<<mh : pure electron multiplication

•HgCdTe is direct semiconductor (unlike Si)

noiseless amplification inside infrared pixel

Avalanche Photo Diode:

band diagram of MOVPE heterojunction

• heterojunction

• widen bandgap at junction

• narrow bandgap in gain region

to boost APD gain

• for low excess noise

take care that all photons are

absorbed in p-type absorber region

• electrons experience

full APD gain

• solid state engineering !

hv

Potential energy

Wide depletion (3.5um) for:

reduced field across jn

max gain for late absorbed photons

Jn

Graded

region

1.0um

Jn in wide bandgap

material (2.0µm)

For reduced g.r. current

and TAT defects

Avalanche in narrow

bandgap material (3.0µm)

Must ensure no

barrier here

Wide bandgap heavily

doped contact region

credit:

Ian Baker SELEX

SAPHIRA ROIC and window topology

• preload regions of interest

• reset region lager than window region to avoid edge effects

window reset

• 320x256 pixels

24μm pitch

• 32 outputs at 5MHz

• Outputs organized in 32

adjacent pixels

• full multiplex advantage

for readout of windows

• readout noise reduced by

Fowler sampling

SAPHIRA unit cell

• unit cell source follower per detector SFD

30fF

EXTREF

• symmetric cryogenic preamp

off chip on focal plane

symmetric cryogenic preamplifiers

cryogenic opamps for 32 channels: OPA354

• cryogenic symmetric preamplifier:

well proven design with Aladdin,

VIRGO and H2RG arrays

• OPA 354:

gain bandwidth 250MHz

noise: 6.5nV/Hz

• Preamp gain 3

• 320 x256 SAPHIRA SELEX eAPD in LCC package

additional cooling plane

for preamplifiers

• standard 2-slot NGC system: front-end basic board (sequencer, clock &bias )

new 32-channel 10 MHz ADC board & preprocessor in FPGA

SAPHIRA readout electronics

ADC

SAPHIRA detector mount for GRAVITY WFS

• science grade array mounted in GRAVITY WFS

lenslet array

is moveable to select

window of 72x72 pixels

on best part

of 320x256 pixel array

IRATEC test camera

test rig:

• Offner relay f/11

• clod filter wheel with

bandpass filters: J,H,K

• test pattern with grid of holes

in image plane illuminated

by extended blackbody

Offner relay

filter wheel

CCC

detector

NIR HgCdTe eAPD: calibrated test pattern

• Offner relay f/11

• clod filter wheel with bandpass filters:

J,H,K

• test pattern with ESO logo in image plane

illuminated by extended blackbody

subelectron sensitivity

• filter H-band

• single double correlated clamp

• chop frequency 10 Hz

• blackbody temperature : on 70C

off 20C

• optics: Offner relay f/11

• fluence

1.5 photons / pixel / integration time

1 electrons / pixel / integration time

for integration time of 1.4 msec

• readout mode:

Fowler 2

• bias voltage 14.4V

Stability of SAPHIRA eAPD

• flatfield in H-band

difference of

TBB=123C and 70C

APD gain = 102

bias=12.6V

T=90K

DIT=8.5ms

• date:

2015-02-08


• flatfield in H-band

difference of

TBB=123C and 70C

APD gain = 102

bias=12.6V

T=90K

DIT=8.5ms

• date:

2015-03-05


• after one month of

continuous cryogenic

operation operability

decreased from

99.6% to 99.5%

at an APD gain of 51

• if array degrades

operability can be

cured by baking array

under vacuum at 60C

SAPHIRA window topology for GRAVITY

• full array 320x256 pixel

frame time 512 μs

• Wavefront sensor:

96x72 pixels needed

3x72 conversion strobes

frame time: 43 μs

Fowler-12 possible

for DIT=1ms

• fringe tracker:

48 spectra to be read

with 24 windows each

having 32x1 pixel

separation 5 rows

24 conversion strobes

frame time: 4.8 μs

Fowler-90 possible for DIT

of 1 ms

subelectron noise with Fowler sampling

• windowed readout 96x72 pixel

• GRAVITY has 9x9

subapertures with 8x8 pixels

(72x72 pixels needed)

• frame time for window 70 µs

• temperature 90K

• at APD gain of 299 and

DIT=140 μs with Fowler-2

the readout noise is

0.14 electrons rms

• for long integration times and

high APD gain readout noise is

dominated by detector dark

current

1 2 324 648 12816 Fowler pairs

APD gain of Mark14

• at bias 19.1V

APD gain = 421

• still well behaved

with excellent

cosmetic quality

excess noise factor F of Mark14

• signal to noise not increased by

avalanche gain

• signal and noise amplified by the

same gain factor

• Excess noise factor F = 1

• APD gain in direct

semiconductor HgCdTe is

noiseless up to gain of 16

Signal-to-noise histogram with & without APD gain

0 100 200 300signal to noise ratio

0

500

1000

1500

2000

2500

Num

ber

of P

ixels

APD agin =16.27

APD agin = 1.00

FILTER K

TBB=125C

DIT=20 ms

excess noise factor F of Mark14

• signal to noise not increased by

avalanche gain

• signal and noise amplified by the

same gain factor

• Excess noise factor F = 1

• APD gain in direct

semiconductor HgCdTe is

noiseless up to gain of 421

Signal-to-noise histograms: SNR with APD gain=16 & SNR with APD gain =421

0 5 10 15signal to noise ratio

0

500

1000

1500

2000

2500

Num

ber

of P

ixels

APD agin =16.27

APD agin = 421.24

FILTER K

TBB=80C

DIT=718 microsec

sensitivity demonstration detecting single photons

• if APD gain is sufficiently high that the

number of electrons generated by one

photon ≫ 𝐾𝑇𝐶 it is not necessary to

use double correlated sampling

• C=56fF T=90K 𝐾𝑇𝐶=52 e- rms

1 photon generates 421 e- at maximum

APD gain which is >> than 𝐾𝑇𝐶

• uncorrelated readout allows to double the

frame rate

• with rolling reset on the new ME1000

SAPHIRA ROIC the duty cycle is 100%

• raw uncorrelated readout achieves

sensitivity to detect signals ~ one

photon/pixel/dit

• H-band, blackbody temperature = 70C,

f/11 camera, frame rate: 1083 fps

single photons detected with uncorrelated readout

• single uncorrelated exposure

• bias: 19.1 V APD gain: 427• integration time : 923 μs

• flux: 1 photon/DIT/pixel

• average of 266 single frames

• chopper frequency: 10 Hz

• cosmetic quality superb

at APD gain of 427 !!

experimental setup for spectral QE measurement

• illuminate entrance slit

of monochromator with

cavity blackbody which

can be heated to 1200C

• calibrate efficiency of

monochromator with

pyroelectric detector

• reimage exit slit of

monochromator to plane

in front of cryostat

window conjugate to

the detector

blackbody

lens

order sorting filter

monochromator

lens

Cryostat

window

Offner cameraNGC

controller

LN2 precooling

QE versus λ of Mark14 eAPD

• QE defined as

Nele/APDgain/Nphot

• at APD gain of 1

λc=3.5 μm

• at high APD gain

λc=2.5 μm

• only photons with

λ<2.5 μm experience

full APD gain

• photons with

λ>2.5 μm get only

partial APD gain

SAPHIRA multiplexer

silicon

AR coating

CdTe substrate transparent for

λ>0.8 μm

λc=2.5 μm HgCdTe

absorber layer

λc=3.5 μm HgCdTe

gain region

MOVPE diode structure

• photons with λ>2.5μm are absorbed in gain region and only get

partial APD gain

• only photons with λ<2.5μm are absorbed in absorber layer and get full APD

λ=3μm

SAPHIRA multiplexer

silicon

AR coating

CdTe substrate transparent for

λ>0.8 μm

λc=2.5 μm HgCdTe

absorber layer

λc=3.5 μm HgCdTe

gain region

MOVPE diode structure

λ=1.5μm

Dark current Mark14

• at high APD gain dark

current does not depend

on temperature

• only process which does

not depend on

temperature is trap

assisted tunneling (TAT)TAT

on-chip temperature diode

• on-chip temperature diode emits light

• light emission limits dark current measurements

• dark current measurement has to be repeated with on-chip temperature diode disconnected

SAPHIRA deployed in GRAVITY on Paranal

• coherently combine light of four 1.8 m auxiliary telescopes in VLTI lab

GRAVITY on Paranal

• coherently combine light of four 1.8 m auxiliary telescopes in VLTI lab

• Integrated optics beam combiner

• 6 combinations of 4 telescopes

• 4 intensities to get phase

• 2 polarizations

• 48 spectra

• narrow angle precision astrometry

• 10µarcsec: OPD < 5nm

SAPHIRA deployed in GRAVITY

• 1 device in fringe tracker

of beam combiner

instrument

• 4 devices in Coude Infrared Adaptive optics

systems CIAO with bimorph mirror

• SAPHIRA in:

GRAVITY on Paranal

SAPHIRA fringe tracker Hawaii-2RG science spectrometer fringe tracker

• fringe tracking sensitivity

• FINITO with PICNIC

mag3

• PRIMA with PICNIC

mag 6

• GRAVITY with SAPHIRA

mag 10

SAPHIRA in CIAO

• Coude Infrared Adaptive Optics

with SAPHIRA array under test

at Max Planck in Heidelberg

• loop open and closed

• all four 8 meter telescopes of

the VLTI will be equipped with

CIAO

• first test in February 2016

credit:

Casey Deen MPIA Heidelberg

E-ELT

• Cerro

Armazones

near Paranal

• elevation:

3064m

• segmented

mirror

• diameter 38m

38 m diameter

65 m high

Deformable

Mirror

Instruments

WFS adaptor

E-ELT

WFS arms

(contain WFS

detectors)Some

instruments

also contain

WFS detectors

WFS adaptor

ELT-CAM: MICADO

• instruments scale with

telescope diameter

• diffraction limited pixel scale

4 milliarcsecond

• large detectors needed

because of fine pixel scale

• field of 1 arcminute requires

mosaic of 4x4 4Kx4K arrays

• too expensive: descope to

mosaic of 3x3 arrays

test of Hawaii-4RG-15 bare multiplexer

H4RG bare multiplexerInterface cable for

32-channel operation

first test with 32-channel

cryogenic preamplifier

board (H2RG heritage)

will be replace with 66-channel

cryogenic preamplifier

setup for first light with Hawaii-4RG-15 bare mux

• illuminate bare mux with glass fiber

fed by halogen lamp

• use ESO 32-channel cryogenic

preamplifier board for 32 channel

operation

• put target pattern in front of detector

and observe shadow image

target

32-channel

cryogenic preamp

first light with H4RG-15 bare mux

• bare multiplexer at room temperature

• raw single image taken with

uncorrelated readout mode

• reference pixel subtraction

• faint shadow image of ESO logo

is reflection of protective glass

H4RG-15 for SUBARU PSF

• Subaru PSF purchased

four H4RG-15

λc=1.7µm arrays

• already delivered

• UH will get first

H4RG15 λc=2.5μm

array of the second

generation grown with

4inch MBE machine

• ESO has MoU with

University of Hawaii to

evaluate first array with

the ESO NGC

controller

• LGSD 1760x1680 optical CMOS array with 700 frames/sec at noise < 3erms

• 70400 single slope ADCs on-chip and 88 LVDS digital outputs

• quarter size prototype NGSD delivered

• e2v head board interfaced to NGC: demonstrates flexibility of NGC platform

• transfer gate: measure charge of

large pixel on small floating

diffusion: single pixel CCD

• low readout noise < 3erms

WFS for the ELT

Laser Guide Star Detector (LGSD)

• on first device using MBS test structure because of on-chip bug

(no digital output with LVDS)

NGSD first electro-optical response

• LVDS fixed

• at 300 fps noise 2.7erms

• higher noise with 700 fps

(to be fixed)

• development takes many

years

• reduce defects by

gettering process

NGSD first light

7171

next step: 1kx1k or 512x512 SAPHIRA eAPD ROIC1

28

co

lum

ns r

efe

ren

ce

pix

els

1024 x 1024 pixels

15

mm

16 mm

• format 1Kx1K with 12 µm pitch

• frame rate 1.22 kFPS

• 64 parallel outputs running at 20 MHz

• readout topology allows multiplex advantage

using all channels in window mode

• frame rate scales with window size

• Reference outputs for EMC cancellation

• variable gain

• phase1: use current HgCdTe pixel pitch of 24 µm, connect every

second row and column: format : 512x512

• phase2: develop HgCdTe pixel pitch of 12 µm, connect every pixel

format : 1Kx1K

• schedule: first prototype samples 18 months after placing order

E-ELT Scientific Detector Requirements

InstrumentNo. of

DetectorsPixel Format Wavelength Range

ELT-CAM

MICADO9 4k x 4k 0.8-2.5um

ELT-IFU

HARMONI

8 4k x 4k 0.95-2.45um

8 4k x 4k 0.47-0.95um

ELT-MIR

METIS

1 1k x 1k 5-28um

4 2k x 2k 3-5um

ELT-MOS6 4k x 4k 0.6-1.7um

6-8 4k x 4k or 6k x 6k 0.37-1.0um

ELT-HIRES3 4k x 4k 0.8-2.45um

5 9k x 9k 0.3-0.8um

ELT-PCS4 4k x 4k 0.95-1.65um

8 4k x 2k 0.6-0.9um

WFS types

High-Order NGS WFS

HARMONI: 1 / 150x150 px / 500Hz

MICADO: 1 / 150x150 px / 500 Hz

METIS: 1 / 450x450 px / 500 Hz

Test Camera: 1 / 740x740 px / 500 Hz

[EPICS: 4 / 240x240 / 2.5 kHz]

[EAGLE: 6 / 120x120 / 500 Hz]

Low-Order NGS WFS

MAORY: 3 / 80x80 px / 500 Hz

3 / 320x256 px / 500 Hz

HARMONI-LTAO: 1 / 80x80 px / 500 Hz

2 / 512x512 px / 500 Hz

METIS-LTAO: 1 / 80x80 px / 500 Hz

2 / 512x512 px / 500 Hz

Tel. Guiding: 3 / 200x200 px / 500 Hz

High-Order LGS WFS

MAORY: 6 / 740x740 px / 700 Hz

HARMONI-LTAO: 6 / 740x740 px / 700 Hz

METIS-LTAO: 6 / 740x740 px / 700 Hz

[EAGLE: 6 / 740x740 px / 700 Hz]

0.5 mm < l < 1 mm CCD 220

1.3 mm < l < 2.5 mm SAPHIRA

l = 0.589 mm NGSD

large SAPHIRA and NGSD

need development

conclusions

• ASIC controller only needed for space, not for ground

• large format 4Kx4K arrays available but expensive

requires de-scoping, persistence is still a problem to be

solved

• ELFN noise of As:Si needs to be optimized for high flux

• large format visible WFS has noise problem and needs

further development

• NIR eAPD technology is mature, large format has to be

developed

• eAPD technology has the potential to provide noiseless large

format NIR focal planes in the near future

Detector Developments at ESO to Prepare for the E-ELT Era

Mark Downing, Gert Finger, Johann Kolb, Derek Ives, Leander Mehrgan, Suzanne Ramsay, Javier Reyes,

Roland Reiss, Olaf Iwert

European Southern Observatory ESO (http://www.eso.org)the end

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