Microscale Adaptive Optical Wavefront Correction

由于光路不均匀造成的相位失真严重限制了一大类用于地地和空间通信、大气成像、医用激光光束聚焦等光学系统的性能。随着空间分辨率的提高和带宽的增加，需要一种集成的自适应光学方法来在微观尺度上并行调制波前。这种合作结合了自适应光学、模拟并行超大规模集成(VLSI)微系统、微制造和液晶分子系统的专业知识，创建了用于高分辨率波前校正的新一代自适应微光学系统，在单个混合光电芯片上集成了10,000多个完全自主的控制元件。自治性是高带宽操作的基础，通过直接在芯片上集成所有自适应功能来获得自治性。在体系结构级，通过对外部提供的任意系统性能指标的并行摄动随机梯度下降优化来实现无模型自适应控制。在物理层面上，通过在自适应控制芯片上集成一种工作在千赫兹范围内的新型快速向列相液晶(LC)来实现微尺度的高速波前控制。采用超薄硅(UTSI)换能器的蓝宝石上硅(SOS)技术为高密度光电集成提供了高质量、低噪声、透明的有源介质。我们将研究夹在两个透明SOS晶片之间的LC材料的微尺度结构，实现具有主动电极的相位调制器阵列，并行执行自适应算法。直接与波面对接。架构和技术创新结合在一起，预计系统性能超过108次控制更新/秒。在速度、密度和成本方面至少比现有的自适应光学系统好1000倍。这个项目将研究和教育整合到一系列项目密集型课程中，研究生和本科生团队将学习设计。自适应光学协处理器的原型和测试，在模拟VLSI中实现，并通过MOSIS制造。自适应协处理器将被配置为外部控制各种快速LC和其他空间光相位调制器，可用于陆军研究实验室(ARL)的实验。此外，我们将利用百富勤半导体公司提供的全尺寸UTSI SOS晶片，与霍普金斯大学在特殊安排下定制，以制作出具有一致光学质量的全集成版本的原型。已经抛光的SOS晶片将在JHU微制造实验室和博尔德非线性系统公司进行后处理。Inc.以图案化和沉积与SOS接触的快速向列相LC以实现快速空间光相位调制。原型自适应微光学系统将在各种自适应光学和成像任务中进行实验演示，包括用于光通信的激光聚焦和稳定。

Phase distortions due to inhomogeneities in the optical path severely limit the perforinancc of a large class of optical systems for ground-to-ground and space communications, imaging through the atmosphere, medical laser beam focusing, among others. Demands on increased spatial resolutions and larger bandwidths call for an integrated approach to adaptive optics that modulates the wavefront in parallel at microscopic scale.This collaborative effort combines expertise in adaptive optics, analog parallel very-large scale integrated (VLSI) niicrosys-tems, microfabrication and liquid-crystal molecular systems to create a new generation of adaptive micro-optical systems for high-resolution wavefront correction, with over 10,000 fully autonomous control elements integrated on a single, hybrid opti-cal/electronic chip. Autonomy is essential for high-bandwidth operation, and is obtained by integrating all adaptive functions directly on-chip.At the architectural level, model-free adaptive control is implemented using parallel perturbation stochastic gradient descent optimization of an arbitrary, externally provided metric of system performance. At the physical level, high-speed wavefront control at micro-scale resolution is obtained by integrating a new type of fast nematic liquid-crystal (LC), operating at kilohertz- range bandwidths, onto the adaptive control chip. Silicon-on-sapphire (SoS) technology with ultra-thin silicon (UTSi) transis-tors provides a high-quality, low-noise, transparent active medium for high-density optical and electronic integration. We will investigate microscale structures of LC material sandwiched in between two transparent SoS wafers, implementing arrays of phase modulators with active electrodes implementing the adaptive algorithms in parallel. directly interfacing with the wave- front. The architectural and technological innovations combine to yield a projected system performance in excess of 108 control updates/sec. at least a factor 1,000 better than presently existing adaptive optics systems in speed, density and cost.This program integrates research and education in a sequence of project-intensive courses, where teams of graduate and undergraduate students learn to design. prototype and test adaptive optics co-processors, implemented in analog VLSI and fabricated through MOSIS. The adaptive co-processors will be configured to externally control a variety of fast LC and other spatial light phase modulators, available for experimentation at the Army Research Laboratory (ARL). In addition, we will make use of full-size UTSi SoS wafers provided by Peregrine Semiconductor, custom-fabricated in a special arrangement with Hopkins, to prototype a fully integrated version of consistent optical quality. The already polished SoS wafers will be post-processed at the JHU Microfabrication Laboratory and at Boulder Nonlinear Systems. Inc.. to pattern and deposit fast nematic LC in contact with SoS for fast spatial light phase modulation. The prototyped adaptive micro-optical systems will be experimentally demonstrated on various adaptive optics and imaging tasks including laser beam focusing and stabilization for optical communications.