Microscale Adaptive Optical Wavefront Correction

由于光路中的不均匀性造成的相位畸变严重限制了用于地对地和空间通信、通过大气成像、医疗激光束聚焦等的大型光学系统的性能。对提高空间分辨率和更大带宽的需求需要一种集成的自适应光学方法，该方法可以在微观尺度上并行调制波前。这项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方面的专业知识，创造了新一代用于高分辨率波前校正的自适应微光学系统，在单个混合光学/电子芯片上集成了超过10,000个完全自主的控制元件。自主性对于高带宽操作至关重要，并且通过将所有自适应功能直接集成在芯片上获得。在体系结构层面，无模型自适应控制是通过对任意外部提供的系统性能指标进行并行扰动随机梯度下降优化来实现的。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带宽范围内的新型快速向列液晶（LC），实现了微尺度分辨率下的高速波前控制。蓝宝石上硅（SoS）技术与超薄硅（UTSi）晶体管为高密度光学和电子集成提供了高质量、低噪声、透明的有源介质。我们将研究夹在两个透明SoS晶圆之间的LC材料的微尺度结构，实现具有有源电极的相位调制器阵列，并行实现自适应算法。与波前直接接触。架构和技术创新结合起来，产生了超过108次控制更新/秒的预期系统性能。在速度、密度和成本上，至少比现有的自适应光学系统好1000倍。该计划将研究和教育整合在一系列项目密集型课程中，研究生和本科生团队学习设计。原型和测试自适应光学协处理器，在模拟VLSI中实现，并通过MOSIS制造。自适应协处理器将配置用于外部控制各种快速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Peregrine Semiconductor提供的全尺寸UTSi SoS晶圆，在霍普金斯大学的特殊安排下定制，以实现一致光学质量的完全集成版本的原型。已经抛光的SoS晶圆将在JHU微加工实验室和博尔德非线性系统公司进行后处理。公司. .以快速空间光相位调制为目的，将快速向列相LC与SoS相接触。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，包括光通信中的激光束聚焦和稳定。

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.