Micromachined silicon deformable mirror

Adaptive Optical System Technologies, 1998

A new silicon deformable minor design is presented which provides high reflectivity, an optical quality continuous surface, and high intensity handling capability. Its features make it useful for a wide range of devices including telescopes, lasers, and photolithographic systems. The mirror architecture is similar to commercial electrostrictive deformable mirrors. A focus corrector built using this architecture exhibited 2.25 microns of actuation at the center through the application of lOOv corresponding to a radius of curvature of -2.4m. A 3Oun thick 1cm diameter silicon mirror exhibited its first mechanical resonance at 2.7kHz. A mirror coated with 100am of gold was shown to be able to withstand 100 kW/cm2 of continuous wave lO64nin intensity for 10 minutes without observable degradation. An active mode-matching experiment was performed showing that 99.5% of a Nd:YAG beam could be coupled to a fmesse 4000 ring cavity.

MEMS Adaptive Optics III, 2009

Tib1e 1. sIEM Defonnalde I\linoi pecificatioi> for 30 Meter Telescope .A() Svstem Actiiati (oUiit 4. III to ii I.UOU 64x01 and 1 (((xl 00) Actuatoi pacin ( lcai Apertui Dianietel 40) miLl ons II) mill to 4t nun tmoke Range >10 uiicmon urfaee Differential Stroke (iieihboriii actuators) >1 imcion Bandwidth >2501) Hz )-Sdh (To to accuracy 10 urn )ueratmne Temperature -1) cleoreec ( Actuatom Yield 990.0 (MC'AU. M( )A( ) 10000 Dnet inn cci ABSTRACT The fabrication and initial performance results of high-aspect ratio 3-dimensional Micro-Electro-Mechanical System (MEMS) Deformable Mirrors (DM) for Adaptive Optics (AO) will be discussed. The DM systems were fabricated out of gold, and consist of actuators bonded to a continuous face sheet, with different boundary conditions. DM mirror displacements vs. voltage have been measured with a white light interferometer and the corresponding results compared to Finite Element Analysis (FEA) simulations. Interferometer scans of a DM have shown that ~9.4um of stroke can be achieved with low voltage, thus showing that this fabrication process holds promise in the manufacturing of future MEMS DM's for the next generation of extremely large telescopes.

Advanced Wavefront Control: Methods, Devices, and Applications II, 2004

The design, manufacture, and testing of optical quality surface micromachined deformable mirrors (DMs) is described. With such mirrors, the shape of the reflective surface can be modified dynamically to compensate for optical aberrations and thereby improve image resolution in telescopes or microscopes. Over several years, we have developed microelectromechanical system (MEMS) processing technologies that allow production of optical quality of surface micromachined mirrors. These process steps have been integrated with a commercial foundry process to produce deformable mirrors of unprecedented quality. The devices employ 140 electrostatic actuators. Measurements of their performance detailed in this paper include 2µm of useful stroke, 3nm position repeatability, >90% reflectivity, and flatness better than 20nm RMS. A chemo-mechanical polishing process has been used to improve surface quality of the mirrors, and a gold coating process has been developed to improve the reflectivity without introducing a significant amount of stress in the mirror membrane. An ion bombardment technique has been developed to flatten mirrors. These silicon based deformable mirrors have the potential to modulate spatial and temporal features of an optical wavefront, and have applications in imaging, beam-forming, and optical communication systems. Design considerations and performance evaluation of recently fabricated DMs are presented.

SPIE Proceedings, 2010

We report on the development of microelectromechanical (MEMS) deformable mirrors designed for ground and space-based astronomical instruments using adaptive optics. These lightweight , low power deformable mirrors will have an active aperture of up to 25.2mm consisting of thin silicon membrane mirror supported by an array of up to 4096 electrostatic actuators exhibiting no hysteresis and sub-nanometer repeatability. The continuous membrane deformable mirrors, coated with a highly reflective metal film, are capable of up to 4µm of stroke, have a surface finish of <10nm RMS with a fill factor of 99.8%. The segmented device has a range of motion of 1um of piston and 600 arc-seconds of tip/tilt simultaneously and a surface finish of 5nm RMS. Presented in this paper are device characteristics and performance results for these devices.

The Advanced Maui …, 2006

We report on the development of micro-electromechanical (MEMS) deformable mirrors designed for ground and space-based astronomical instruments intended for imaging extra-solar planets. Three different deformable mirror designs, a 1024 element continuous membrane (32x32), a 4096 element continuous membrane (64x64), and a 331 hexagonal segmented tip-tilt-piston are being produced for the Planet Imaging Concept Testbed Using a Rocket Experiment (PICTURE) program, the Gemini Planet Imaging Instrument, and the visible nulling coronograph developed at JPL for NASA's TPF mission, respectively. The design of these polysilicon, surface-micromachined MEMS deformable mirrors builds on technology that was pioneered at Boston University and has been used extensively to correct for ocular aberrations in retinal imaging systems and for compensation of atmospheric turbulence in free-space laser communication. These light-weight, low power deformable mirrors will have an active aperture of up to 25.2mm consisting of thin silicon membrane mirror supported by an array of 1024 to 4096 electrostatic actuators exhibiting no hysteresis and sub-nanometer repeatability. The continuous membrane deformable mirrors, coated with a highly reflective metal film, will be capable of up to 4µm of stroke, have a surface finish of <10nm RMS with a fill factor of 99.8%. The segmented device will have a range of motion of 1um of piston and a 600 arc-seconds of tip/tilt simultaneously and a surface finish of 1nm RMS. The individual mirror elements in this unique device, are designed such that they will maintain their flatness throughout the range of travel. New design features and fabrication processes are combined with a proven device architecture to achieve the desired performance and high reliability. Presented in this paper are device characteristic and performance results of these devices.

MEMS Adaptive Optics V, 2011

Adaptive optics for the next generation of extremely large telescopes (30 -50 meter diameter primary mirrors) requires high-stroke (10 microns), high-order (100x100) deformable mirrors at lower-cost than current technology. Lowering the cost while improving the performance of deformable mirrors is possible using Micro-Electro-Mechanical Systems (MEMS) technology. In this paper the fabrication and testing of an array of high-stroke gold MEMS X-beam actuators attached to a continuous gold facesheet will be described. Both the actuator and the facesheet were fabricated monolithically in gold plated onto a thermally matched ceramic-glass substrate (WMS-15) using a high-aspect ratio fabrication process.

SPIE Proceedings, 2000

A silicon micromachined deformable mirror QiDM) has been developed by Boston University and Boston Micromachines Corporation (BMC). The pDM employs a flexible silicon mirror supported by mechanical attachments to an array of electrostatic parallel plate actuators. The integrated system of mirror and actuators was fabricated by surface micromachining using polycrystalline silicon thin films. The mirror itself measures 3 mm x 3 mm x 3 jim, supported by a square array of 140 electrostatic parallelelectrode actuators through 140 attachment posts. Recently, this pDM was characterized for its electromechanical and optical behavior and then integrated into two laboratory-scale adaptive optics systems as a wavefront correction device. Figures of merit for the system include stroke of 2 jim, resolution of 10 nm, and frequency bandwidth of 6.7 kHz. The device is compact, exhibits no hysteresis, and has good optical quality.

Micromachines

A large-area and ultrathin MEMS (microelectromechanical system) mirror can provide efficient light-coupling, a large scanning area, and high energy efficiency for actuation. However, the ultrathin mirror is significantly vulnerable to diverse film deformation due to residual thin film stresses, so that high flatness of the mirror is hardly achieved. Here, we report a MEMS mirror of large-area and ultrathin membrane with high flatness by using the silicon rim microstructure (SRM). The ultrathin MEMS mirror with SRM (SRM-mirror) consists of aluminum (Al) deposited silicon nitride membrane, bimorph actuator, and the SRM. The SRM is simply fabricated underneath the silicon nitride membrane, and thus effectively inhibits the tensile stress relaxation of the membrane. As a result, the membrane has high flatness of 10.6 m−1 film curvature at minimum without any deformation. The electrothermal actuation of the SRM-mirror shows large tilting angles from 15° to −45° depending on the applied D...

Advanced Wavefront Control: Methods, Devices, and Applications IV, 2006

Presented in this paper is the development of a 4096 element continuous membrane deformable mirror under development for the Gemini Planet Imaging instrument designed for extra solar planet detection. This deformable mirror will enable the next generation of adaptive optics ("Extreme" AO) capable of achieving contrasts of up to 10 8 , required to detect these planets that are obscured by the brightness of its parent star. This surface micromachined MEMS deformable mirror will have an active aperture of 25.2mm consisting of thin silicon membrane mirror supported by an array of 64x64 electrostatic actuators exhibiting no hysteresis and sub-nanometer repeatability. This deformable mirror will be capable of 4µm of stroke, have a surface finish of <10nm RMS with a fill factor of 99.8%, and be capable of frame rates in excess of 2.5kHz. This development effort combines new design features, fabrication processes and packaging methods with those developed for commercially available 1024 and 140 element MEMS deformable mirrors to achieve unprecedented performance and reliability.

International Conference on Space Optics — ICSO 2000, 2017