Revolutionary visible and infrared sensor detectors for the most advanced astronomical AO systems

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1 Revolutionary visible and infrared sensor detectors for the most advanced astronomical AO systems Philippe Feautrier a,b 1, Jean-Luc Gach b,c, Sylvain Guieu a, Mark Downing d, Paul Jorden e, Johan Rothman f, Eric de Borniol f, Philippe Balard b,c, Eric Stadler a,b, Christian Guillaume g, David Boutolleau b, Jerome Coussement h, Johann Kolb d, Norbert Hubin d, Sophie Derelle i, Clélia Robert i, Julien Tanchon j, Thierry Trollier j, Alain Ravex j, Gérard Zins a, Pierre Kern a, Thibaut Moulin a, Sylvain Rochat a, Alain Delboulbé a, Jean-Baptiste Lebouquin a ; a Institut de Planétologie et d'astrophysique de Grenoble, UJF-Grenoble 1, CNRS-INSU, Domaine Universitaire, 414 rue de la Piscine, BP Grenoble Cedex 9, France; b First Light Imaging, Hôtel Technoptic, Rue Marc Donadille, Marseille cedex 13, France ; c LAM, Laboratoire d'astrophysique de Marseille, Technopôle de Château-Gombert - 38, rue Frédéric Joliot-Curie Marseille, France; d ESO, Karl-Schwarzschild-Strasse 2, Garching bei München, Germany; e e2v technologies,16 Waterhouse Lane, Chelmsford, Essex, CM1 2QU, England; f CEA/LETI - Minatec Campus - 17 rue des Martyrs Grenoble Cedex 9- France ; g OHP, Observatoire de Haute Provence, 487 St.Michel l'observatoire, France; h SOFRADIR, rue Camille Pelletan, 9229 Châtenay-Malabry, France; i ONERA, Chemin de la Hunière, Palaiseau Cedex, France; j Absolut Systems, 32 rue de la Tuilerie, 3817 Seyssinet-Pariset, France. ABSTRACT Since the CCD22 and OCAM2 major success, new detector developments started in Europe. Funded by ESO and the FP7 Opticon European network, the NGSD CMOS device is fully dedicated to Natural and Laser Guide Star AO for the E-ELT with strong ESO involvement. The NGSD will be a 88x84 pixels CMOS detector with a readout noise of 3 e (goal 1e) at 7 Hz frame rate and providing digital outputs. A camera development, based on this CMOS device and also funded by the Opticon European network, is presented in this paper. Another major AO waveront sensing detector development concerns IR wavefront sensing based on Avalanche Photodiode (e-apd) arrays within the RAPID project. Developed by the SOFRADIR and CEA/LETI manufacturers, the latter offers a 32x255 8 outputs 3 microns IR array, sensitive from.4 to 3 microns, with lesse than 2 e readout noise at 16 fps. A rectangular window can also be programmed to speed up even more the frame rate in the case the full frame readout is not useful. The high QE response, in the range of 7%, is almost flat over this wavelength range. Advanced packaging with miniature cryostat using pulse tube cryocoolers was developed for this programme in order to allow use on this detector in any type of environment. The characterization results of this device are presented here. Readout noise as low as 1.7 e at 16 fps has been measured with a 3 microns wavelength cut-off and a multiplication gain of 14 obtained with a modest photodiode polarization of 8V. This device also exhibits excellent linearity, lower than 1%. The pulse tube cooling allows smart and easy cooling down to 55 K. Vibrations measurements using centroiding and FFT measurements were performed to prove that the miniature pulse tube does not induce measurable vibrations to the optical bench, allowing use of this cooled device without liquid nitrogen and with difficult environmental conditions. A successful test of this device on sky on the VLTI PIONIER 4 telescopes instrument at ESO Paranal in June 214. First Light Imaging, which will commercialize a camera system using also APD infrared arrays with the Selex Saphira device in its proprietary wavefront sensor camera platform. These programs are held with several partners, among them are the French astronomical laboratories (LAM, OHP, IPAG), the detector manufacturers (e2v technologies, Sofradir, CEA/LETI) and other partners (ESO, ONERA, IAC, 1 Contact address: philippe.feautrier@obs.ujf-grenoble.fr; phone: ; fax:

2 GTC). Funding is: Opticon FP7 from European Commission, ESO, CNRS and Université de Provence, Sofradir, ONERA, CEA/LETI the French FUI (DGCIS), the FOCUS Labex and OSEO. Keywords: Adaptive optics, Electron Multiplying CCD, EMCCD, L3Vision CCD, Avalanche photodiodes, HgCdTe, low readout noise, wavefront sensor, sub-electron noise. 1. INTRODUCTION The success of the next generation of ESO (European Southern Observatory) instrument [1] for 8 to 1-m class telescopes will depend on the ability of Adaptive Optics (AO) systems to provide excellent image quality and stability. This will be achieved by increasing the sampling and correction of the wave front error in both spatial and time domains. For example, advanced Shack Hartmann systems currently fabricated require 4x4 sub-apertures at sampling rates of khz as opposed to 14x14 sub-apertures at 5 Hz of previous AO systems. Beyond the e2v CCD5 developed for the ESO NACO instrument in the late nineties [2], new detectors of 24x24 pixels are required to provide the spatial dynamics of 5-6 pixels per sub-aperture. Higher temporal-spatial sampling implies fewer photons per pixel therefore the need for much lower read noise (<<1e-) and negligible dark current (<< 1e-/pixel/frame) to detect and centroid on a small number of photons. This detector development was jointly funded by ESO and the OPTICON European network [3] in the Joint Research Activity JRA2 [4], Fast Detectors for Adaptive Optic". e2v technologies [5] was chosen in 25 to develop a dedicated detector based on an extension of their L3Vision [6] EMCCD technology. Analysis [7] showed that the sub-electron read noise of L3Vision CCDs clearly outperformed classical CCDs even though L3Vision devices exhibit the excess noise factor F of 21/2 typical of EMCCDs [8],[9]. During these years, a revolution appeared for infrared detectors with HgCdTe avalanche photodiodes arrays providing outstanding sensitivity and speed. This paper starts to describe this infrared revolution story and one of its development, the RAPID programme. 2. THE RAPID E-APD INFRARED WAVEFRONT SENSING DETECTOR 2.1 The RAPID 32x255 pixel e-apd array presentation Infrared HgCdTe Avalanche Photo Diodes (APD) have been shown to exhibit single carrier multiplication (SCM) of electrons up to gains in the order of 1 associated with low excess noise factors F= , record high gainbandwidth product GBW>2.1THz and low dark currents. The technology used to manufacture APDs is similar to the one used for standard n on p HgCdTe diodes explaining why a high quantum efficiency (typically QE=8-95 %) is maintained from the visible wavelengths up to the infrared (IR) cut-off wavelength. They have inspired a large effort in developing focal plan arrays using HgCdTe APDs for low photon number applications such as active imaging in the range gated mode (2D) and/or with direct time of flight detection (TOF) (3D) and, more recently, passive imaging for wave front correction and fringe tracking in astronomical observations [11] funded by the RAPID programme. The RAPID programme is a 4 years R&D project funded by the French "Fonds Unique Interministériel" in 29. It includes several industrial and academic partners from the field of advanced infrared focal plane arrays fabrication (SOFRADIR, CEA-LETI) and of astronomical/defense institutes (IPAG, LAM, ONERA). The goal of this programme is to develop a fast and low noise infrared focal plane array of moderate format for astronomical fast application like adaptive optics wavefront sensing and fringe tracking for astronomical interferometers. The main characteristics of RAPID are: Pixels Format: 32 x 255 pixels 3µm pitch Technology: HgCdTe, intra-pixel CDS and CTIA, 3 to K

3 Rectangular window can be defined with the start line and the end line of the window to be read. Noise: 1.5 e- with gain x3 Frame rat: 15 Hz, up to 2 Hz Dark signal: 1 e-/s measured, limited by setup background Power consumption: 122 mw The e-apd HgCdTe technology allows to apply moderate multiplication gain without adding noise, therefore lowering the readout noise without almost no penalty. This is the only way to obtain the fast frame rates needed by wavefront sensing with readout noise lower than 2 e. This kind of performances can t be achieved by classical HgCdTe arrays, the APD technology is absolutely necessary. The ultimate goal of the RAPID development is to demonstrate operation of the 32x255 pixels 3 microns pitch infrared array at 2 fps with less than 2 e- readout noise. To achieve such readout noise and fast frame rate, APDs technology and intra-pixel Correlated Double Sampling were both needed. The floor plan of the device is shown in the Fig. 1, it includes 8 parallel outputs clocked at 2 MHz pixel rate defining 8 stripes of 4x256 pixels with one amplifier per stripe. The detector can be seen in the Fig. 2 during its integration in the pulse tube cryostat. Start line Fig. 1. the 1.6 kfps RAPID e-apd infrared detector configuration: 8 outputs 32 x 255 pixels with 3 µm pitch. A rectangular window with programmable start line and end line can be defined to speed up the frame rate. Fig. 2. the RAPID 32x255 IR APD array during integration by Sofradir in its cryostat cooled with a miniature pulse tube.

4 2.2 RAPID results The multiplication gain of the APD mainly depends on the cut-off wavelength and the reverse bias voltage of the photodiode, also but with less sensitivity depends on the detector temperature. The gain increases with the bias voltage, the cut-off wavelength and decreases with the temperature. The bias voltage of the photodiode, performed by the readout circuit, is driven by the CMOS technology used for the readout circuit. Increasing the cut-off wavelength increases the gain but also the dark signal and the need for colder temperature. A first trade-off of these constrains was to choose a cut-off wavelength of 3 to 3.3 µm with a CMOS technology well proven by SOFRADIR allowing -8V of reverse bias. The conversion gain is calibrated using the classical photon transfer curve method by plotting the variance of the signal to the square as a function of the signal. The Fig. 3 shows such a photon transfer curve of the RAPID infrared device with a photodiode reverse bias of 8V equivalent to a mean multiplication gain of x13.9. Variance (adu) 2 Variance (adu) 2 Variance (adu) 2 Variance (adu) x e/adu output Mean - Bias (adu).224 e/adu output Mean - Bias (adu).232 e/adu 1 5 output Mean - Bias (adu).224 e/adu output Mean - Bias (adu) Variance (adu) 2 Variance (adu) 2 Variance (adu) 2 Variance (adu) Mean - Bias (adu).219 e/adu Fig. 3: photon transfer curve of the RAPID infrared device with a photodiode reverse bias of -8V equivalent to a mean multiplication gain of x13.9. The multiplication gain is computed by plotting linearity curves (signal versus time) under various photodiode polarisation. At.9 V photodiode polarisation, the multiplication gain is 1 and the slope of the linearity curve is e/adu output 1 output Mean - Bias (adu).232 e/adu output Mean - Bias (adu).222 e/adu output Mean - Bias (adu)

5 measured. When the photodiode polarisation is higher than.9 V, the multiplication gain M is higher than 1. The linearity curve of the slope is also measured with this gain M. The multiplication gain is computed by dividing the 2 measured slopes, assuming that the illumination conditions did not vary during the 2 data recording. Mean level (adu) e+4 adu/s output Time (s) 3.962e+4 adu/s Mean level (adu) e+4 adu/s output Time (s) 3.469e+4 adu/s Mean level (adu) Mean level (adu) output Time (s) 3.68e+4 adu/s output Time (s) 2.339e+4 adu/s Mean level (adu) Mean level (adu) output Time (s) 2.729e+4 adu/s output Time (s) 1.769e+4 adu/s Mean level (adu) 2 1 output Time (s) Mean level (adu) output Time (s) Fig. 4: linearity curve of RAPID with a photodiode polarization of -8V. The slope of this curve is measured for each photodiode polarization for further multiplication gain M measurement.

6 Multiplication gain M Photodiode polarisation (V) Multiplication gain M Output Output 1 Output 2 Output 3 Output 4 Output 5 Output 6 Output Photodiode polarisation (V) Fig. 5: multiplication gain as a function of the photodiode reverse bias for RAPID 3 m cut-off device. Up: the multiplication gain is averaged for the 8 outputs; Down: the multiplication gain is plotted for each of the 8 outputs showing a very low dispersion of the multiplication gain over the multiple outputs RAPID detector. The system noise is computed using frames of 2 images recorded in dark conditions using black cover on the cryostat window and a very small integration time (1 µs). The RMS noise is computed using the temporal variance of each pixel from the 2 frames data cube recorded in these conditions. Noise in digital units of the ADC is converted in e by using the conversion gain measured at unity gain for which the excess noise factor F is 1. Then the noise is computed input

7 referred by dividing the previous noise in e by the multiplication gain measured with the linearity slope method described above. The resulting noise histograms of the 8 detector outputs are shown in Fig. 6 at 16 fps and gain of Mean readout noise as low as 1.62 e have been measured with the RAPID IR array at 16 fps and a multiplication gain of Number of count Number of count Number of count Number of count Median noise output =1.65 e pixel value (adu) Median noise output 2 =1.67 e pixel value (adu) Median noise output 4 =1.82 e pixel value (adu) Median noise output 6 =1.37 e pixel value (adu) Number of count Number of count Number of count Number of count Median noise output 1 =1.56 e pixel value (adu) Median noise output 3 =1.63 e pixel value (adu) Median noise output 5 =1.73 e pixel value (adu) Median noise output 7 =1.56 e pixel value (adu) Fig. 6. RMS Noise histogram of 32x255 RAPID 3 m cut-off device per output at 16 fps and gain Mean RMS readout noise is 1.62 e in these conditions.

8 The readout noise variation as a function of the multiplication gain at 16 fps and a detector temperature of 75K is shown in Fig Readout noise input referred (e) Multiplication gain M Fig. 7: RMS mean readout noise as a function of the multiplication gain for RAPID 3 m cut-off device. RAPID output non linearity The linearity error of the output signal versus input irradiance is defined as the maximum discrepancy between the measured output signal and an ideal. The least squares is applied to those points. A plot of linearity error versus signal in electrons will be calculated using the following equation: % 1 where Signal x indicates the signal level and Signal x indicates the maximum signal level in e. The output non-linearity is the difference between the maximum and minimum linearity errors over the considered range. The Fig. 8 shows the output non-linearity for each of the 8 output of the RAPID device at very low signal level (-5 e range). Over this range at very low level signal, we measure an output non-linearity of 1% in average.

9 Linearity (%) Linearity (%) Linearity (%) output Mean level (e) output Mean level (e) output Mean level (e) output 6 Linearity (%) Linearity (%) Linearity (%) output Mean level (e) output Mean level (e) output Mean level (e) output 7 Linearity (%) Linearity (%) Mean level (e) Mean level (e) Fig. 8. Output non-linearity for each of the 8 output of the RAPID device at very low signal level (-5 e range). The output non-linearity is 1% in average. An important specification of our system is the ability to be used in a vibration free environment. This is why we investigated the system vibrations by imaging a 1 µm pinhole on the infrared array using a SWIR focusing objective mounted with a C-mount on the cryostat. The centroid of the pinhole image is computed as well as the jitter (in pixels) of this centroid. The FFT of this jitter allows to obtain the jitter spectrum as shown in the Fig. 9. This figure shows that no vibrations due to our 5 Hz miniature pulse tube cooler can be measured.

10 Fig. 9. jitter spectrum of the spot centroid demonstrating no vibrations induced by the 48 Hz drive pulse tube cooler. The RAPID device described in this paper will now replace the infrared PICNIC detector of the PIONIER [1] 4 telescopes visitor instrument installed on the ESO VLTI in Paranal, see Fig. 1. For the first time in the world, an APD infrared array was installed on an operating astronomical instrument on a big telescope facility. A first technical run of 5 days was performed in June 214, the camera was installed on the instruments and was tested during 4 technical nights. Additional technical run are foreseen in the months to come in 214 with upgraded performances. The detector is cooled using a miniature pulse tube providing vibrations free 1.5 W of cooling power at 8K without the need of liquid nitrogen operation. Detector cooling down to 55 K is achievable at the highest cooling power with this system. In operation, the detector is cooled at 78K in order to limit the pulse tube power and increase its lifetime. No vibrations have been detected on the instrument due to the pulse tube operation. The first technical mission was a success, the camera worked without any major issue on the sky and 4 telescope fringes tracking was achieved at first attempt on the sky. A full description of this project and of this technical run is given elsewhere in this conference by Sylvain Guieu [11]. Fig. 1: (left) the RAPID cryostat in operation in Paranal, on the PIONIER VLTI visitor instrument in June 214 inside the ESO Paranal VLTI laboratory; (right) Part of the RAPID team shipping the RAPID system in Paranal from Grenoble France in May THE OCAM 2K CAMERA The FIRST LIGHT IMAGING [12] spin-off now commercializes most of these fast detectors developments and is specialized on very fast and low noise camera for scientific applications like adaptive optics and interferometry. Many camera systems have been sold by this company in the world to the best astronomical telescopes.

11 The now well-known OCAM2 camera, see Fig. 11, is commercialized by First Light Imaging [12]. OCAM2 is a readyto-use camera with embedded parameters to run the CCD, factory optimized. OCAM2 has also been designed for ruggedness and can cope with more demanding environmental conditions, like accepting cooling water temperature up to 35 C and removing the need for an external chiller. The camera is fully sealed, includes the Thermo Electric Cooler controller inside the camera head, and needs only a standard +24V power supply for the whole system. Fig. 11. the OCAM2 camera, 24x24 pixels EMCCD, from 1.5 to 2 kfps, <.2 e noise, commercialized by First Light Imaging [12]. The OCAM2 system is capable of driving all members of the CCD22/219 family at their nominal speed (1.5kframes/s) and transmitting the data at full speed through a CameraLink interface. The camera controller is able to drive deep depleted variants with multilevel clocking at voltage levels up to 24V with speeds of more than 1Mlines/s. The controller handles the 8 L3vision outputs with high voltage clocking up to 5V voltage swing. A big effort has been made to have high voltage stability (less that 1mV/hour of drift) in order to ensure a constant gain over a long period. The system digitizes the CCD signal using correlated double sampling with 14 bits resolution. Standard interfacing of the camera is performed by using a PC computer running Windows OS fitted with a CameraLink full grabber and a proprietary software capable of gathering in real time the extremely high data rate of 22Mbytes/s produced by the camera. By clocking pixels at 18.6 MHz, OCAM2 moved to OCAM2K [13] and is now able to acquire images at 2 Kfps without performances degradation, as shown in Table 1. Readout noise as low as.13 e was obtained at 2 kps and gain 1 with the 24x24 pixels EMMCCD of OCAM2K, see Table 1. Table 1. OCAM2 and OCAM2K performances comparison Test measurement OCAM2 OCAM2K Unit Nominal speed (full frame) fps Mean readout noise (full frame, full speed), gain e- Pure Latency 6 43 µs Dark signal at full speed and temperature -45 C.23.2 e-/pix/frame Detector operating temperature C Peak Quantum Efficiency at 65 nm % Linearity at gain x1 from 1 to 15 ke <3 <3 % Image area Full Well Capacity at gain x1, 153 fps 3 3 ke- Parallel CTE at gain x1, 153 fps N/A Serial CTE at gain x1, 153 fps N/A

12 1 Noise input (e) Multiplication gain Output Output 1 Output 2 Output 3 Output 4 Output 5 Output 6 Output 7 Fig. 12: OCAM2K readout noise at 2 kfps as a function of the multiplication gain. The OCAM2K readout noise as a function of the multiplication gain is shown in Fig. 12. Readout noise below.2 e at 2 frames/s can easily be achieved as shown in this figure. The Fig. 13 shows the OCAM2K readout noise histogram at 2 fps and multiplication gain x1. Readout noise of.12 e can be achieved in these conditions. Another version of OCAM2, called OCAM2S, was also recently developed by First Light Imaging with an electronic shutter allowing to precisely synchronize the integration time with an external trigger. This original development is described elsewhere in this conference by Jean-Luc Gach [14].

13 Histogram gaussian fit Pixel value histogram 14 x 15 RMS noise =.12 e 12 1 Number of count pixel value input referred (e) Fig. 13: OCAM2K readout noise histogram at 2 fps and multiplication gain x1. Readout noise as low as.12 e can be achieved in these conditions. 4. THE NGSD BSI CMOS 88X84 DETECTOR FOR LASER GUIDE STAR A new fast detector development in the visible has been started by ESO and the OPTICON network in 28 to develop new detector devices in the E-ELT framework, both for NGS and LGS wavefront sensing on extremely large telescopes [15]. The same consortium with ESO, e2v technologies and the French astronomical observatories (LAM, IPAG and OHP) decided to develop a long term program for this goal with joint funding from ESO and OPTICON under the 7th Framework Programme. Very early in the project, it has been decided to move to new detector technologies based on CMOS devices. But if CMOS devices are now commonly used in low cost applications, this is not the case for demanding scientific imaging. To mitigate the risk of this technological step, the long term programme was divided into several phases, up to the LGSD (Laser Guide Star Detector) which is the final development. The different phases are "Technology Demonstrators" (TVP), the "Natural Guide Star Detector" (NGSD) and the LGSD. The main issue with Laser Guide Star wavefront sensing is the spot elongation due to the finite distance of the laser guide star produced by the stimulation of the sodium layer of the atmosphere at about 9 km. This cone effect due to the angle between the telescope axis and the laser beam axis induces that LGS spots are elongated. The main consequence is that the LGS sub-aperture requires more pixels than with NGS whereas all other parameters of the AO detector remain the same: frame rate, pixel size, quantum efficiency, dark current and up to a certain level the readout noise. Maintaining fast frame rate (~ 1 khz) and low readout noise

14 lower than 3 e while increasing the detector format is impossible with the current detector technology. This is the reason why a new devices family is under development to cover this new exciting challenge for the E-ELT. The main specifications of the NGSD are given in Table 2. In addition, First Light Imaging is developing a compact camera system based on this device. This camera will be available by 215. This development is fully described elsewhere in this conference [16] by Mark Downing. Table 2. the NGSD 88x84 BSI CMOS device for LGS wavefront sensing. Pixel number (including dark reference pixels) Detector technology Pixel Pitch 24µm Pixel topology Sub-aperture Array architecture Natural Guide Star Detector NGSD - 88x84 pixels with 84x84 sensitive pixels Thinned backside illuminated CMOS.18µm 4T pinned photodiode pixel 2x2 pixels Pixel full well 4 e- Read noise including ADC ADCs configuration Number of parallel LVDS channels 22 Serial LVDS channel bit rate Frame rate 42x42 sub-apertures of 2x2 pixels < 3. e-rms 2 x 88 column ADCs, 9 (goal 1) bits 21 Mb/s baseline, up to 42 Mb/s (desired) 7 fps up to 1 fps with degraded performance 5. CONCLUSION This paper illustrates a long term and coordinated wavefront sensor development in Europe involving cutting edge detectors and camera systems industry associated with ESO, academic French laboratories (LAM, IPAG and OHP) and the First Light Imaging spin off. Wavefront sensing detector developments are now carried out in Europe for the next generation of telescopes. Among them, a big eefort is currently placed on infrared wavefront sensors devices. One of this infrared device is called RAPID and is based on a 2 kfps 32x255 pixels infrared APD arrays. This device is currently tested on the sky, already demonstrating on sky read noise lower of 1.7 e at this frame rate. A first technical run of this device has been done on the ESO VLTI in June 214. This was the first time ever that an infrared APD array was successfully used on a big telescope facility and an operating astronomical instrument. This infrared detector is produced by SOFRADIR. A commercial camera based on e-apd array will be commercialized by First Light Imaging [1]. Apart this, a long programme has started in 24 for developing large CMOS detectors for the E-ELT with several phases, all detectors are fabricated by e2v. The current phase consist in the production of a 88x8 pixel fully digital CMOS detector which should provide 3 e- read noise at 7 Hz (1 Hz with degraded performances) and optimal QE. This detector, called NGSD, will be used for natural and laser guide start systems on Extremely Large Telescopes. A camera system based on the NGSD, commercialized by First Light Imaging, will be offered by 215.

15 6. ACKNOWLEDGMENTS These developments have been partly carried out using OPTICON and FUI funds. OPTICON is supported by the European Commission's FP7 Capacities programme (Grant number 22664). The RAPID programme was funded by the Fonds Unique Interministériel (FUI) under the 7th AAP from the French "Ministère de l'economie, des Finances et de l'emploi". Funding is also: ESO, CNRS, Université de Provence, Sofradir, ONERA and CEA/LETI. This work is also partially supported by the LabEx FOCUS ANR-11-LABX-13. REFERENCES [1] Moorwood, A., "Instrumentation at the ESO VLT ", Proc. SPIE 6269, (26). [2] Feautrier, P., Kern, P. Y., Dorn, R. J., Rousset, G., Rabou, P., Laurent, S., Lizon, J., Stadler, E., Magnard, Y., Rondeaux, O., Cochard, M., Rabaud, D., Delboulbe, A., Puget, P., Hubin, N. N., "NAOS visible wavefront sensor" in Adaptive Optical Systems Technology, ed. by Peter L. Wizinowich, SPIE Proc. Vol. 47, pp (2). [3] Gillmore, G. F., "OPTICON: a (small) part of European astronomy", Proc. SPIE 5382, 138 (24). [4] Feautrier, P., Fusco, T., Downing, M., Hubin, N., Gach, J-L., Balard, P., Guillaume, C., Stadler, E., Boissin, O., Jorden, P., Diaz, J-J., "Zero noise wavefront sensor development within the Opticon European network", Scientific Detectors for Astronomy 25, Springer Netherlands editor, ISBN: , Beletic, Jenna E.; Beletic, James W.; Amico, Paola (Eds.), Vol. 336 (26). [5] e2v technologies, [6] Jerram, P., Pool, P. J., Bell, R., Burt, D. J., Bowring, S., Spencer, S., Hazelwood, M., Moody, I., Catlett, N. and Heyes, P. S., "The LLCCD: low-light imaging without the need for an intensifier", in Proc. SPIE, 436, pp , May 21. [7] Fusco, T., Nicolle, M., Rousset, G., Michau, V., Beuzit, J-L, Mouillet, D., "Optimisation of Shack-Hartman based wavefront sensor for XAO systems", Advancements in Adaptive Optics. Edited by Domenico B. Calia, Brent L. Ellerbroek, and Roberto Ragazzoni. Proceedings of the SPIE, Volume 549, pp (24). [8] Robbins, M., Hadven, B., "The Noise Performances of Electron Multiplying Charge-Coupled Devices", IEEE Transactions On Electron Devices, Vol. 5, No. 5, pp (23). [9] Petit, C., Fusco, T., Charton, J., Mouillet, D., Rabou, P., Buey, T., Rousset, G., Sauvage, J.-F., Baudoz, P., Gigan, P., Kasper, M., Fedrigo, E., Hubin, N., Feautrier, P., Beuzit, J.-L., Puget, P., "The SPHERE XAO system: design and performance", Proc. SPIE 715, 7151D (28). [1] J.-B. Le Bouquin, J.-P. Berger, B. Lazareff, G. Zins, P. Haguenauer, L. Jocou, P. Kern, R. Millan-Gabet, W. Traub, O. Absil, J.-C. Augereau, M. Benisty, N. Blind, X. Bonfils, P. Bourget, A. Delboulbe, P. Feautrier, M. Germain, P. Gitton, D. Gillier, M. Kiekebusch, J. Kluska, J. Knudstrup, P. Labeye, J.-L. Lizon, J.-L. Monin, Y. Magnard, F. Malbet, D. Maurel, F. Ménard, M. Micallef, L. Michaud, G. Montagnier, S. Morel, T. Moulin, K. Perraut, D. Popovic, P. Rabou, S. Rochat, C. Rojas, F. Roussel, A. Roux, E. Stadler, S. Stefl, E. Tatulli and N. Ventura, PIONIER: a 4-telescope visitor instrument at VLTI, A&A, Volume 535, November 211, DOI: [11] Sylvain Guieu, Philippe Feautrier, Eric Stadler, Johan Rothman, Michel Tauvy, Jean-Baptiste Le Bouquin, Gérard Zins, Pierre Kern, Jérome Coussement, Eric D. de Borniol, Jean-Luc Gach, Marc Jacquart, Thibaut Moulin, Sylvain Rochat, Alain Delboulbé, Sophie Derelle, Clélia Robert, Michel Vuillermet, RAPID: a revolutionary fast optical to NIR camera applied to interferometry, SPIE Astronomical instrumentation and telescopes Montreal 214 conference proceedings, Paper , Optical and Infrared Interferometry IV, Montreal, 214. [12] First Light Imaging SAS, [13] Gach et al., First results of a 2+ frame per second OCAM2, proceedings of the AO4ELT3 conference, Florence 213, [14] Jean-Luc Gach, Philippe Feautrier, Philippe Balard, Christian Guillaume, Eric Stadler, OCAM2S: an integral shutter ultrafast and low noise wavefront sensor camera for laser guide stars adaptive optics systems, Paper , SPIE Astronomical instrumentation and telescopes Montreal 214 conference proceedings, Paper , Adaptive Optics Systems IV, Montreal, 214.

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