A solid state yet rapidly tunable filter based on liquid crystal (LC) etalon technology is designed by determination of minimized LC birefringence response time in an optimized electric field. The key technological innovation is the use of liquid crystal to tune the etalon. While this type of etalon has been in use for many years, a development effort is undertaken to reduce the time it takes to tune a LC etalon over a free spectral range from a few milliseconds (current state of the art) to 100-500 microseconds (proposed). The primary application of this technology is integration into a space based lidar (light detection and ranging) system, particularly in differential absorption lidar (DIAL) systems. DIAL is one of the most powerful active remote sensing techniques due to its spatial and altitude resolution, measurement precision, and insensitivity to surface emissivity. As such, it can be used to monitor spatial and temporal changes of minor molecular atmospheric constituents in the lower troposphere. The filter is designed for observing water vapor from orbit. An accurate assessment of global water vapor distribution is key to more precise modeling of climate feedback from clouds and improved weather forecasting.
The primary application is the provision of fast frequency tuning for space based lidar systems. However, the proposed tunable etalon can be modified for use in on-orbit hyperspectral imaging systems or high speed dynamics sampling. A promising non-lidar application is micro-scale sampling of atmospheric winds or measuring the O2-A band emission to determine temperature profiles at high temporal cadence.
Non-government applications include use as a spectral sensor for narrow spectral signatures with applications in the oil and gas markets, both exploration and leak and pollution detection. Mineral detection and the detection of chemical impurities in minerals as well as agriculture are also potential applications. All of these markets are looking to expand their observational capabilities and will experience high degree of growth over the next decade.