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Tilted pressure-tuned field-widened Michelson interferometer for high spectral resolution lidar

High spectral resolution lidars (HSRLs) designed for aerosol and cloud remote sensing are increasingly being deployed on aircraft and called for on future space-based missions. The HSRL technique relies on spectral discrimination of the atmospheric backscatter signals to enable independent, unambiguous retrieval of aerosol extinction and backscatter. NASA Langley Research Center is developing a tilted pressure-tuned field-widened Michelson interferometer (FWMI) to achieve the spectral discrimination for an HSRL system. The FWMI consists of a cubic beam splitter, a solid glass arm, and a sealed air arm. The spacer that connects the air arm mirror to the main part of the interferometer is designed to minimize thermal sensitivity. The pressure of the sealed air-arm air can be accurately controlled such that the frequency of maximum interference can be tuned with great precision to the transmitted laser wavelength. In this paper, the principle of the tilted pressure-tuned FWMI for HSRL is presented. The pressure tuning rate, the tilted angle requirement and challenges in building the real instrument are discussed.