SBIR Phase II: A Large Mosaic Liquid Crystal Fabry-Perot Etalon for Atmospheric Sensing

该小型企业创新研究(SBIR)第二阶段项目解决了法布里-珀罗涉仪(FPI)输入孔径的传统尺寸限制。这一限制(大约8英寸)是由以下因素造成的：(1)对可抛光到表面数字lambda/100的玻璃平板尺寸的实际制造限制；(2)成本限制。虽然可以使用较小的玻璃板阵列来扩大FP I的收集区域，但在阵列单元上协调光谱扫描需要笨重的控制系统，否则使用传统的气压或压电式FRI系统是不可能的。这项研究建立了创新的FP I标准具阵列，在FP I谐振腔中使用液晶(LC)。这些器件的光谱扫描是通过对施加到玻璃基板上的导电层施加小电流来完成的。谐振腔中施加在液晶上的电场改变了液晶的取向，从而改变了材料在谐振腔中的折射率。易于电子控制的FP I腔中的折射率允许多个LC填充单元的简单、低重量、低功率的协调，从而使FP I单元的大阵列成为可能，同时扫描光谱。第二阶段将设计和制造两个直径10英寸的LC FP(LC FP)滤光片阵列。将配置一个阵列用于大气发射的多普勒测量，另一个阵列用于0.16纳米光谱分辨率的测量。潜在的商业应用包括(1)大气激光雷达，(2)天基环境传感，(3)被动气辉传感，(4)晴空湍流探测，(5)目标探测。

This Small Business Innovation Research (SBIR) Phase II project addresses the traditional size limit of the Fabry-Perot interferometer (FPI) input aperture. This limit (approximately 8-inches) is imposed by (1) practical fabrication limits to the size of glass flats that can be polished to a surface figure of lambda/100 and (2) by cost limitations. Although an array of smaller glass plates might be used to expand the collecting area of the FPI, coordination of spectral scans over the array elements requires unwieldy control systems or else is not possible with conventional barometric or piezo-electric FRI systems. This research establishes arrays of innovative FPI etalons that use liquid crystal (LC) in the FPI resonant cavity. Spectral scanning of these devices is accomplished by application of a low current to conducting layers applied to the glass substrates. The electric field imposed upon liquid crystal in the resonant cavity alters the orientation of the LC, and thus the index of refraction of the material in the resonant cavity. The ease of electronic control over the refractive index in the FPI cavity permits simple, low weight, low power coordination of multiple LC filled cells and thus makes possible a large array of FPI cells, scanning a spectrum in unison. Phase II will design and fabricate two 10-inch diameter arrays of LC FPI (LCFP) filters. One array will be configured for Doppler measurements of atmospheric emissions and the other for 0.16-nanometer spectral resolution.Potential commercial applications are expected in (1) atmospheric lidar, (2) space-based environmental sensing, (3) passive airglow sensing, (4) clear-air turbulence detection, and (5) target detection.