Continuous Facesheet Deformable Mirror Research Articles

Seventh-order wavefront modulation with a gravity-neutral optofluidic deformable phase plate

A 63-electrode optofluidic refractive wavefront modulator enabling spatial frequency correction up to the seventh radial Zernike order, the highest spatial order ever achieved with a refractive dynamic wavefront modulator, is presented. The modulator is designed so that aberration correction performance is nearly identical in both horizontal and vertical orientations, virtually eliminating the gravity-induced parasitic surface deformations typical for optofluidic devices. With 55 of its electrodes located within the 1-cm clear pupil, the modulator offers the versatility of continuous face-sheet deformable mirrors within a compact, high efficiency, and transmissive device. Using a fluidic interfacing method based on wafer-level 3D micro-structuring of glass, the modulator is only 0.86-mm-thick, facilitating the cascading of multiple modulators within close proximity. We demonstrate a bi-directional stroke of more than 13 λ, and replications of Zernike mode shapes up to the seventh radial order with high fidelity, representing a significant leap in the performance of ultra-miniaturized refractive wavefront modulators.

LSPV+7, a branch-point-tolerant reconstructor for strong turbulence adaptive optics.

Optical wave propagation through long paths of extended turbulence presents unique challenges to adaptive optics (AO) systems. As scintillation and branch points develop in the beacon phase, challenges arise in accurately unwrapping the received wavefront and optimizing the reconstructed phase with respect to branch cut placement on a continuous facesheet deformable mirror. Several applications are currently restricted by these capability limits: laser communication, laser weapons, remote sensing, and ground-based astronomy. This paper presents a set of temporally evolving AO simulations comparing traditional least-squares reconstruction techniques to a complex-exponential reconstructor and several other reconstructors derived from the postprocessing congruence operation. The reconstructors' behavior in closed-loop operation is compared and discussed, providing several insights into the fundamental strengths and limitations of each reconstructor type. This research utilizes a self-referencing interferometer (SRI) as the high-order wavefront sensor, driving a traditional linear control law in conjunction with a cooperative point source beacon. The SRI model includes practical optical considerations and frame-by-frame fiber coupling effects to allow for realistic noise modeling. The "LSPV+7" reconstructor is shown to offer the best performance in terms of Strehl ratio and correction stability-outperforming the traditional least-squares reconstructed system by an average of 120% in the studied scenarios. Utilizing a continuous facesheet deformable mirror, these reconstructors offer significant AO performance improvements in strong turbulence applications without the need for segmented deformable mirrors.

A 19 Element Hexagonal Actuator Arrangement Continuous Face-Sheet MEMS Deformable Mirror

A new hexagonal actuator arrangement continuous face-sheet MEMS deformable mirror is proposed, a mirror array with 19 elements is fabricated by a surface micromachining process. This design has a good fitting capability and a fast dynamic response. The fabricated sample is tested by an optical profiler. Simulation and test results indicate that it has a small aperture size, a high fill factor, a fast response time and a high working bandwidth. This new device provides a possibility of manufacturing a large-actuator-count DM for high speed wavefront control.

High-Surface-Quality and Wider-Modulation-Range Continuous Face-Sheet Micro Deformable Mirror Based on SOI

A new type of continuous face-sheet micro deformable mirror was designed and fabricated based on SOI (Silicon-on-Insulator) technology for high optical efficiency applications in adaptive optics system. SOI provided a Silicon-Insulator-Silicon structure, and the insulator-layer of the three-layer structure was taken as etch-stop layer in deep silicon etching, which made the suspended bulk silicon membrane obtained easily. And the reflective face did not suffer etch-step due to the protection of insulator-layer. The mirror was composed of 5-um-thick and 10-mm-diameter flexible bulk silicon membrane, and actuated by 69 electrostatic actuators which evaporated on glass substrate. SOI and glass wafer were bonded together by anodic bonding, forming a separation gap of 15um between the mirror face and electrostatic pad, which offered a maximum effectual displacement of 5um by considering the pull-in effect. Fabrication process was introduced in detail. Bulk silicon micromachining was employed, methods mainly include Inductivity Coupled Plasma (ICP) etching and Si/Glass anodic bonding technique.

Liquid crystal wavefront corrector with modal response based on spreading of the electric field in a dielectric material

A novel liquid crystal (LC) wavefront corrector with smooth modal influence functions is proposed and realized. The device consists of a thin layer of planar aligned nematic LC sandwiched between a glass plate with a conductive electrode and a plate made of ceramic material with a very high dielectric constant. Control electrodes are positioned on the back side of the ceramic plate, opposite to the LC. The modal character of the response is determined by spreading of the electric field in the ceramic plate. The device implemented is operating in a reflective (mirror) mode; however, similar principles can be used to build a transmissive device. Low cost and simplicity of control make it a good alternative to continuous face-sheet deformable mirrors.

Modal liquid crystal wavefront corrector

Results are presented of the properties of a liquid crystal wavefront corrector for adaptive optics. The device is controlled using modal addressing in which case the device behaves more like a continuous facesheet deformable mirror than a segmented one. Furthermore, the width and shape of the influence functions are electrically controllable. We describe the construction of the device, the optical properties, and we show experimental results of low order aberration generation.