Continuous Membrane Deformable Mirror Research Articles

AlN-based piezoelectric MEMS deformable mirror.

An AlN-based piezoelectric micro-electromechanical system (MEMS) continuous membrane deformable mirror (DM) prototype is presented for the first time. Its effective aperture diameter is 5 mm and it is equipped with 25 independently controlled actuators. Owing to the advantages associated with the AlN piezoelectric thin-film technology, attractive characteristics including CMOS compatible fabrication, bidirectional linear and negligible hysteresis actuation, and excellent linear superposition control capability have been successfully demonstrated. Moreover, good optical aberration correction performance is also validated via the surface contour fitting experiment to the Zernike polynomials up to the first 14 orders despite the non-optimized device structure design, representing great application perspective.

Large-scale membrane transfer process: its application to single-crystal-silicon continuous membrane deformable mirror

This paper describes a large-scale membrane transfer process developed for the construction of large-scale membrane devices via the transfer of continuous single-crystal-silicon membranes from one substrate to another. This technique is applied for fabricating a large stroke deformable mirror. A bimorph spring array is used to generate a large air gap between the mirror membrane and the electrode. A 1.9 mm × 1.9 mm × 2 µm single-crystal-silicon membrane is successfully transferred to the electrode substrate by Au–Si eutectic bonding and the subsequent all-dry release process. This process provides an effective approach for transferring a free-standing large continuous single-crystal-silicon to a flexible suspension spring array with a large air gap.

Silicon-on-insulation-based deformable mirror array for adaptive optics

In this paper, the authors present a continuous membrane deformable mirror array based on silicon-on-insulator (SOI) bulk micromachining technology for applications in adaptive optics. In order to facilitate the use of the device layers of SOI wafers for the reflective surface and electrostatic actuators, the fabrication of the micromirror array is separated from the electronics chip, and then they are bonded together using the flip-chip assembly. The optical reflective membrane formed by the device layer of one SOI wafer is of high quality in terms of flatness and surface roughness; the stroke space is mainly determined by the height of the device layer of another wafer. The simulation results of the actuator performance by the finite element analysis method shows that the stroke is up to 2μm at about 70V actuation voltage and the frequency is about 17.8kHz.

Single-Crystal-Silicon Continuous Membrane Deformable Mirror Array for Adaptive Optics in Space-Based Telescopes

In this paper, we present a single-crystal-silicon (SCS) continuous membrane deformable mirror (DM) as a corrective adaptive-optics (AO) element for space-based telescopes. In order to correct the polishing errors in large aperture (~8 m) primary mirrors, a separate high-quality surface DM array must be used. Up to 400000 elements and a mirror stroke of ~100 nm are required for the correction of these polishing errors. A continuous membrane mirror formed by the the SCS device layer of a silicon-on-insulator (SOI) wafer is used to achieve a high-quality optical surface and to minimize the additional diffractive effects in the optical system. To achieve substantial local deformation needed to correct high-order errors, we use a highly deformable silicon membrane of 300-nm thickness. This thin membrane is able to deform locally by 125 nm at an operating voltage of 100 V with a pixel pitch of 200 mum. The resonance frequency of a pixel is 25 kHz with a low Q-factor of 1.7 due to squeeze-film damping. The device is fabricated by processing the microelectromechanical system (MEMS) and electronic chips separately and then combining them by flip-chip bonding. This allows optimization of the MEMS and electronics separately and also allows the use of an SOI layer for the mirror by building the MEMS bottom up. A small prototype array of 5times5 pixels with 200-mum pitch is fabricated, and we demonstrate single pixel and multiple pixel actuation