GeSiSn PIN detector arrays for beam alignment in coherent Doppler LiDAR systems

A key future earth science mission for NASA focuses on the global characterization of vertical profiles of horizontal wind magnitude and direction. The ldquo;3D Windsrdquo; mission targets both coherent and direct detection Doppler wind lidars to complement one another in a hybrid lidar system in low Earth orbit. Optimum performance of a coherent Doppler wind lidar system necessitates the use of an optical beam alignment architecture, such as one of those previously described.nbsp;In this proposal, Freedom Photonics outlines a path towards improved optical alignment within an existing coherent Doppler lidar system at NASA Langley Research Center through the development of an inexpensive alignment detector system with high bandwidth and quantum efficiency, which is responsive at target wavelengths between 1.9 and 2.2 micro;m. Prototype Germanium Silicon Tin (GeSiSn) PIN detector arrays developed on a synergistic program are already responsive out to 2.2 micro;m wavelengths. Critically, the GeSiSn material can be grown directly on Si substrates, which are inexpensive to process and allow for growth on large-diameter wafers and thus large high-resolution arrays and/or large detector apertures. This program will leverage Freedom Photonicsrsquo;s extensive experience in the design, fabrication, and manufacture of complex photodiodes and systems, as well as existing materials to support a rapid development effort. The overall goal of this SBIR program, through Phases I, II, and III, is to develop, transfer to manufacturing, qualify, and transition to NASA deployment, as well as other government andnbsp;commercial markets, a low cost, radiation hard, high quantum efficiency shortwave infrared photodiode array using the GeSiSn materials system, grown on a Silicon substrate.nbsp;