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
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)
XSHOOTER spectrum of SN1987A
courtesy Jason Spyromilio
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
XSHOOTER spectrum of SN1987A
courtesy Jason Spyromilio
• 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
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
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:
2015-03-05
Stability of SAPHIRA eAPD
• 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
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
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
Top Related