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Next-generation infrared astronomical instrumentation for ground-based and space telescopes requires MOEMS-based programmable slit masks for multi-object spectroscopy. We made a full space evaluation of Texas Instruments DMD chips, including tests at cold temperature and in vacuum, life tests, radiations, and vibrations and shocks. These results do not reveal any show-stopper concerning its ability to meet environmental space requirements. In parallel, a 100×200µm2 micro-mirror array was successfully designed for cryogenic temperature, fabricated and tested at 92K. Large micromirror arrays of 20'000 micromirrors have also been fabricated. These tests demonstrate the full ability of this type of components for space instrumentation.

We are developing MEMS-based programmable reflective slit masks for future generation infrared multi-object spectroscopy (MOS) for space and ground-based telescopes. These devices are composed of monocrystalline silicon micromirrors of size 200 x 100 um(2) which can be tilted by electrostatic actuation yielding a tilt-angle of 20 degrees. An electromechanical clamping mechanism has been demonstrated providing uniform tilt-angle within one arc minute precision over the whole array (5 x 5 micromirrors). Slit masks of different sizes have been produced; the largest one measures 25 x 22 mm(2) and is composed of 20'000 micromirrors. Thanks to the architecture and the fabrication process of these slit masks; the micromirror peak-to-valley deformation (PTV) is uniform over the device and was measured being below 10 nm for uncoated micromirror. A slit mask of size 5 x 5 micromirrors was successfully tested in cryogenic conditions at 92 K; the micromirrors were actuated before, during and after the cryogenic experiment. To achieve for the large arrays a better fabrication yield and a higher reliability, the architecture, the process flow, the assembly and the electronics are being optimized. Optical characterizations as well as experiments of the large devices are underway.

Multi-object spectroscopy (MOS) is a powerful tool for space and ground-based telescopes for studying the formation of galaxies. This technique requires a programmable slit mask for astronomical object selection. A first sample of MEMS-based programmable reflective slit masks with elements of size 200x100 mu m(2) has been successfully tested in cryogenic conditions at 92 K. Devices of larger size were microfabricated, the largest chip measures 25x22 mm(2) and is composed of 200x100 electrostatic actuated micromirrors. These devices are composed of two chips: the electrode chip and the mirror chip, which are processed separately and assembled consecutively. The mirror chip is bonded on top of the electrode chip and microfabricated pillars on the electrode chip provide the necessary spacing between the two parts. A process flow utilizing refilling techniques based on borophosphosilicate glass (BPSG) deposition and reflow was developed. Programmable reflective slit masks based on this fabrication process were microfabricated and characterized. These devices exhibit a micromirror deformation of 11 nm peak-to-valley and an actuation voltage of 145 V for a tilt angle of 9 degrees. Preparation of samples for MOS experiments are underway.

We demonstrate the capabilities of a new optical microelectromechanical systems device that we specifically developed for broadband femtosecond pulse shaping. It consists of a one-dimensional array of 100 independently addressable, high-aspect-ratio micromirrors with up to 3 mu m stroke. We apply linear and quadratic phase modulations demonstrating the temporal compression of 800 and 400 nm pulses. Because of the device's surface flatness, stroke, and stroke resolution, phase shaping over an unprecedented bandwidth is attainable. (C) 2010 Optical Society of America

We are developing a linear array of micromirrors designed for optical, femtosecond laser pulse shaping. It is a bulkmicromachined device, capable of retarding or diminishing certain laser frequencies in order to perform phase and amplitude modulation within a frequency band spanning the UV to the near-infrared. The design consists of a linear array of mirrors fixed on either side by springs. They feature two degrees of freedom: Out-of-plane motion for phase shifting and rotational motion for binary amplitude modulation, both realized using vertical comb drives. The first applications will include femtosecond discrimination experiments on biomolecules.

Next-generation infrared astronomical instrumentation for telescopes requires MOEMS-based programmable slit masks for multi-object spectroscopy. A large micromirror array of 20'000 micromirrors has been fabricated for cryogenic environment utilizing a dedicated assembly stage. Preliminary tests demonstrate the functionality of both the assembly system and the device.

Next generation of infra-red astronomical instrumentation for space telescopes as well as ground-based extremely large telescopes requires MOEMS devices with remote control capab ility and cryogenic operation, including programmable multi-slit masks for mu lti-object spectroscopy (MOS). For the complete testing of these devices, we have developed in parallel and coupled a high-resolu tion Twyman-Green interferometer and a cryogenic-chamber for full surface and operation characterization. The interferometer exhibits a nanometer accuracy by using phase-shifting technique and low-coherence source. The cryogenic-chamber has a pressure as low as 10e-6 mbar and is able to cool down to 60K. Specific interfaces minimizing stresses for vacuum and cryo have been set. Within the framework of the European program on Smart Focal Planes, micro-mirrors have been sel ected for generating MOEMS-based slit masks. A first 5x5 micro-mirror array (MMA) with 100x200µm 2 mirrors was successfully fabricated using a combination of bulk and surface silicon micromachining. They show a mechanical tilting angle of 20° at a driving voltage below 100V, with excellent surface quality and uniform tilt-angle. The mirrors could be successfully actuated before, during and after cryogenic cooling. The surface quality of the gold coated micro-mirrors at room temperature and below 100K, when they are actuated, shows a slight increase of the deformation from 35nm peak-to-valley to 50nm peak-to-v alley, due to CTE mismatch between silicon and gold layer. This small deformation is still well within the requiremen t for MOS application. Keywords : micro-mirror array, mu lti-object spectrograph, MOEMS.

We are developing micromirror arrays (MMA) for future generation infrared multiobject spectroscopy (MOS) requiring cryogenic environment. So far we successfully realized small arrays of 5 x 5 single-crystalline silicon micromirrors. The 100 mu m x 200 mu m micromirrors show excellent surface quality and can be tilted by electrostatic actuation yielding 20 degrees mechanical tilt-angle. An electromechanical locking mechanism has been demonstrated that provides uniform tilt-angle within one arc minute precision over the whole array. Infrared MOS requires cryogenic environment and coated mirrors, silicon being transparent in the infrared. We report on the influence of the reflective coating on the mirror quality and on the characterization of the MMA in cryogenic environment. A Veeco/Wyko optical profiler was used to measure the flatness of uncoated and coated mirrors. The uncoated and unactuated micromirrors showed a peak-to-valley deformation (PTV) of below 10nm. An evaporated 10nm chrome/50nm gold coating on the mirror increased the PTV to 35nm; by depositing the same layers on both sides of the mirrors the PTV was reduced down to 17nm. Cryogenic characterization was carried out on a custom built interferometric characterization bench onto which a cryogenic chamber was mounted. The chamber pressure was at 10e-6 mbar and the temperature measured right next to the micromirror device was 86K. The micromirrors could be actuated before, during and after cryogenic testing. The PTV of the chrome/gold coated mirrors increased from 35nm to 50nm, still remaining in the requirements of < lambda/20 for lambda=1 mu m.

We are developing single-crystalline silicon micromirror arrays (MMA) for future generation infrared multiobject spectroscopy (IRMOS). Arrays of 5times5 gold-coated micromirrors were packaged and tested at below 100 K. The gold-coating and the cryogenic compatibility are crucial for the application in an IR MOS. The micromirrors could be actuated before, during and after cryogenic testing. The surface deformation of the uncoated 100 mum times 200 mum micromirrors is below 10 nm peak-to-valley (PTV), 35 nm for single-side gold coated mirrors and 17 nm for double-side gold coating. In cryogenic environment the PTV of the gold coated mirrors increased from 35 nm to 50 nm, thus still remaining in the requirements of 1 mum.

We are fabricating a bulk-micromachined micromirror device for laser pulse shaping applications on femtosecond time scales. An array of micromirrors is used to individually retard or diminish certain laser frequencies spanning from the UV to the near-infrared. The individual mirrors are fixed by two springs on either side and can be tilted (amplitude modulation) or moved out-of plane (phase modulation) using asymmetrical or symmetrical vertical comb drives, respectively.

Micromirror arrays are promising components for generating reflective slit masks in future multiobject spectrographs. The micromirrors, 100 mum times200 mum in size, are etched in bulk single crystal silicon, whereas a hidden suspension is realized by surface micromachining. The micromirrors are actuated electrostatically by electrodes located on a second chip. The use of silicon on insulator (SOI) wafers for both mirror and electrode chip ensures thermal compatibility for cryogenic operation. A system of multiple landing beams has been developed, which latches the mirror at a well-defined tilt angle when actuated. Arrays of 5times5 micromirrors have been realized. The tilt angle obtained is 20deg at a pull-in voltage of 90 V. Measurements with an optical profiler showed that the tilt angle of the actuated and locked mirror is stable with a precision of 1 arcmin over a range of 15 V. This locking system makes the tilt angle independent from process variations across the wafer and, thus, provides uniform tilt angle over the whole array. The surface quality of the mirrors in actuated state is better than 10-nm peak to valley and the local roughness is about 1-nm root mean square

We report on micromirror arrays being developed for object selection in Multi Object Spectrographs for astronomical applications. The micromirrors are etched in bulk single crystal silicon whereas the cantilever type suspension is realized by surface micromachining. One micromirror element is 100μm × 200μm in size. The micromirrors are actuated electrostatically by electrodes located on a second chip. The use of silicon on insulator (SOI) wafers for both mirror and electrode chip ensures thermal compatibility for cryogenic operation. A system of multiple landing beams has been developed, which passively locks the mirror at a well defined tilt angle when actuated. The mechanical tilt angle obtained is 20° at a pull-in voltage of 90V. Measurements with an optical profiler showed that the tilt angle of the actuated and locked mirror is stable with a precision of one arc minute over a range of 15V. This locking system makes the tilt angle merely independent from process variations across the wafer and thus provides uniform tilt angle over the whole array. The precision on tilt angle from mirror to mirror measured is one arc minute. The surface quality of the mirrors in actuated state is better than 10nm peak-to-valley and the local roughness is around 1nm RMS. Preliminary cryogenic tests showed that the micromirror device sustains 120K without any structural damage.

Silicon-based photonic MEMS modulate light by displacing microoptical elements such as micromirrors and microlenses. Recent development focus on fiber-laser couplers, multi-object spectrometers, and tunable cavities.

MOEMS devices are under study in order to be integrated in next-generation astronomical instruments for ground-based and space telescopes. Their main advantages are their compactness, scalability, specific task customization using elementary building blocks, and remote control. Several laboratories, including Laboratoire d'Astrophysique de Marseille in close collaboration with microtechnology institutes, are engaged since several years in the design, realization and characterization of programmable slit masks for multi-object spectroscopy and micro-deformable mirrors for wavefront correction. First prototypes have been developed and show results matching with the requirements.

Micromirror arrays are being developed dedicated for astronomical instrumentation. We report on the strategy to handle a large number of micromirrors needed for covering a 0.5 m times 0.5 m large active surface and on cryogenic characterization.

Devices based on SOI technology are subject to bow due to residual stress induced by the buried oxide. We have designed and fabricated a compact tunable piston tip-tilt mirror device in which the shape and the arrangement of the suspension beams result in both a reduced stress in the suspension beams and an optically flat mirror. The piston tip-tilt mirror is characterized by an accurate vertical displacement of up to 18 mm @ 80 V with good repeatability, and a tip-tilt of up to 2 mrad @ 50 V.

We report on micromirror arrays being developed for the use as re”ective slit mask in Multi Object Spectrographsfor astronomical applications. The micromirrors are etched in bulk single crystal silicon whereas the cantilevertype suspension is realized by surface micromachining. One micromirror element is 100 µ m x 200 µ m in size. Themicromirrors are actuated electrostatically by electrodes located on a second chip. The use of silicon on insulator(SOI) wafers for both mirror and electrode chip ensures thermal compatibility for cryogenic operation. A systemof multiple landing beams has been developed, which passively locks the mirror at a well de“ned tilt angle whenactuated. The mechanical tilt angle obtained is 20 at a pull-in voltage of 90V. Measurements with an opticalpro“ler showed that the tilt angle of the actuated and locked mirror is stable with a precision of one arc minuteover a range of 15V. This locking system makes the tilt angle merely independent from process variations acrossthe wafer and thus provides uniform tilt angle over the whole array. The precision on tilt angle from mirror tomirror measured is one arc minute. The surface quality of the mirrors in actuated state is better than 10nmpeak-to-valley and the local roughness is around 1nm RMS.Keywords: micromirror, multi object spectroscopy, MOEMS, mirror array, DRIE

Observing the formation of early galaxies helps us understand our origins. The light coming from these faraway objects is very faint and shifted to the infrared. Multi-object spectroscopy (MOS) is the central method for studying many isolated objects simultaneously, using a slit mask in the focal plane of the telescope for blocking spoiling sources and background light. Today these masks are static perforated sheets or complex fiber-opticbased systems. In the future, microelectromechanical systems (MEMS) could provide a remote controllable, reconfigurable slit mask, increasing the scientific efficiency of MOS. In the framework of studies on the future European Extremely Large Telescope (E-ELT), we are developing a micromirror array (MMA)-based reflective slit mask. Another MEMS solution, a microshutter-based slit mask, is being developed for the James Webb Space Telescope by Moseley and colleagues at NASA.1 However, we believe that MMAs are an appropriate solution for extremely large telescopes (ELTs), as they have a large focal plane (in the meter range). Because we work with reflected light, the electric wiring and mounting of the MEMS can be realized under the MMA. These integrated MMA building blocks can be used as ‘paving stones’ to cover large surfaces nearly seamlessly. Figure 1 shows the basic concept of a MOS using an MMA as a slit mask. The mirrors at the locations of the objects of interest are tilted (ON state), and the light is sent toward the spectrograph. All the other mirrors remain unactuated (OFF state) and send the light of the spoiling sources back to the telescope. The ratio of wanted to unwanted light must be 3000:1 or better. Thus a mechanical tilt angle of at least 20◦ is needed.2 This tilt angle must be uniform across the whole array, so that the light of all selected objects goes through the entrance pupil of the spectrograph. In order not to disturb the wavefront of the reflected light, the mirror must remain optically flat (λ/20) during operation. For infrared applications, it must be in a cryogenic environment. Figure 1. In the multi-object spectroscopy microelectromechanical systems (MOS-MEMS) setup, the micromirror array in the focal plane of the telescope selects the light from the objects of interest and sends it to the spectrograph.

Next generation MOS for space as well as ground-based instruments, including NIRSpec for JWST, require a programmable multi-slit mask. A promising solution is the use of MOEMS-based devices such as micromirror arrays (MMA) or micro-shutter arrays (MSA). Both configurations allow remote control of the multi-slit configuration in real time. Engaged in the design studies for NIRSpec, we have developed different tools for the modelling and the characterization of these devices. Since, we have continued our studies with commercial TI MMA and we show that in a 20° ON-OFF configuration, the 3000 contrast requirement is fulfilled for any F# of 8m-class telescopes as well as future ELT's. Within the framework of the JRA on Smart Focal Planes, micro-mirrors have been selected in order to get a first demonstrator of a European MOEMS-based slit mask. We have fixed several key parameters: one micromirror per astronomical object, high optical contrast of at least 3000, tilting angle of 20°, fill factor of more than 90%, size of a micro-element around 100 × 200 μm 2 , driving voltage below 100V. The MMA would also work in a wide range of temperature down to cryogenic temperatures. Based on these parameters, we have designed a new MMA architecture, using a combination of bulk and surface micromachining. A first small test array of micro-mirrors was successfully fabricated and shows the desired mechanical tilting angle of 20° at a driving voltage of about 100V. Preliminary measurements show a surface quality better than lambda/20. Assembly of small test arrays with their electrode chips and design of larger arrays are under way.

Micromirror arrays have been fabricated dedicated to astronomical instrumentation. The 100times200 mum2 sized micromirrors show an excellent optical surface quality and can be electrostatically tilted by 20deg. A system of multiple landing beams have been implemented, which forces uniform tilt angle

A novel concept for video-rate parallel acquisition of optical coherence tomography imaging based on in-pixel demodulation is presented. The main restrictions for parallel detection, like data rate, power consumption, circuit size and poor sensitivity are overcome with a smart pixel architecture. An offset compensation circuit, a synchronous sampling stage, programmable time averaging and random pixel accessing are incorporated in-pixel, allowing envelope and phase detection in large 1D and 2D arrays.

We report on micromirror arrays being developed for use as reflective slit masks in multiobject spectrographs for astronomical applications. The micromirrors are etched in bulk single crystal silicon, whereas cantilever-type suspension is realized by surface micromachining. One micromirror element is 100200 m in size. A system of multiple landing beams is developed, which electrostatically clamps the mirror at a well-defined tilt angle when actuated. The mechanical tilt angle obtained is 20 deg at a pull-in voltage of 90 V. Measurements with an optical profiler show that the tilt angle of the actuated mirror is stable with a precision of one arc minute over a range of 15 V. This electrostatic clamping system provides uniform tilt angle over the whole array: the maximum deviation measured between any two mirrors is as low as one arc minute. The surface quality of the mirrors in the actuated state is better than 10 nm peak-to-valley and the local roughness is around 1-nm rms. Cryogenic testing shows that the micromirror device is functional at temperatures below 100 K.

Next-generation infra-red astronomical instrumentation for space and ground-based telescopes requires MOEMS-based programmable slit masks for multi-object spectroscopy (MOS) usable in a cryogenic environment. A 100x200 mum2 micro-mirror array was successfully designed, fabricated and tested, with tilting angle of 20deg at 100 V. In parallel we have developed and implemented a high-resolution Twyman-Green interferometer and a cryo-chamber for full surface and operation characterization. The micromirrors could be successfully actuated before, during and after cryogenic cooling. Surface deformation of gold coated mirrors at 300 K and below 100 K shows a slight increase from 35 nm to 50 nm PtV, still well suited for MOS application.