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

这个小型企业创新研究（SBIR）第二阶段项目解决了法布里-珀罗干涉仪（FPI）输入孔径的传统尺寸限制。 这一限制（约8英寸）是由（1）实际制造限制可抛光到λ/100表面图形的玻璃平面的尺寸和（2）成本限制所强加的。 虽然可以使用较小玻璃板的阵列来扩大FPI的收集区域，但是在阵列元件上的光谱扫描的协调需要笨拙的控制系统，或者对于传统的气压或压电FRI系统是不可能的。 这项研究建立了创新的FPI标准具阵列，在FPI谐振腔中使用液晶（LC）。 这些装置的光谱扫描通过将低电流施加到施加到玻璃衬底的导电层来实现。 施加在谐振腔中的液晶上的电场改变LC的取向，并且因此改变谐振腔中的材料的折射率。 在FPI腔中的折射率的电子控制的容易性允许多个LC填充单元的简单、低重量、低功率的协调，并且因此使得FPI单元的大阵列一致地扫描光谱成为可能。 第二阶段将设计和制造两个10英寸直径的LC FPI（LCFP）滤波器阵列。 一个阵列将被配置为用于大气排放的多普勒测量，另一个将被配置为0.16纳米的光谱分辨率。潜在的商业应用预计在（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，和（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.