Confocal Fabry-Perot interferometer based high spectral resolution LIDAR
Hoffman, David Swick
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A high spectral resolution lidar (HSRL), which has been developed at Montana State University, utilizes a confocal Fabry-Perot interferometer (CFP) to separate aerosol and molecular lidar returns for the purpose of atmospheric aerosol observation. The CFP is actively frequency locked to the laser-transmitter via a novel frequency modulation based technique. 532 nm second harmonic light from a frequency doubled Nd:YAG injectionseeded, pulsed laser is directed vertically into the atmosphere. Light backscattered by the atmosphere is collected using a commercial Schmidt-Cassegrain telescope. The secondharmonic return signal is mode matched into a tunable CFP interferometer with a free spectral range of 7.5 GHz and a finesse of 50.7 (312) at 532 nm (1064 nm) placed in the optical receiver for spectrally filtering the molecular and aerosol return signals. The light transmitted through the CFP is used to monitor the aerosol return signal while the light reflected by the CFP is used to monitor the molecular return signal. Data collected with the HSRL are presented and inversion results are compared to those from a co-located solar radiometer, demonstrating the successful operation of the instrument. The HSRL presented in this dissertation provides an important means to study atmospheric aerosols, which are the largest source of uncertainty in current global climate models. Additionally, the novel frequency locking technique allows for the future development of multi-wavelength HSRL instruments, and the robustness of the frequency locked optical filter allows for the deployment of future air and space based HSRL instruments.