12 December 2006 300mJ injection seeded compact 2 micron coherent lidar transmitter
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Abstract
The design of a compact coherent laser radar transmitter for tropospheric wind sensing is presented. This system is hardened for ground and airborne applications. As a transmitter for a coherent wind Lidar, this laser has stringent spectral line width and beam quality requirements. Although the absolute wavelength is not fixed, the output wavelength should avoid atmospheric CO2 and H2O absorption lines. The design architecture includes a seed laser, a power oscillator and a single amplifier. The laser material used for this application is a Ho:Tm:LuLF crystal. The 3-meter long folded ring resonator produces 100-mJ with a temporal pulse length around 185 ns. A final output of 300 mJ at a repetition rate of 10 Hz is achieved by using an amplifier in a double pass format. The operating temperature is set around 15°C for the pump diode lasers and 5°C for the rod. Since the laser design has to meet high-energy as well as high beam quality requirements, close attention is paid to the laser head design to avoid thermal distortion in the rod. A side-pumped configuration is used and heat is removed uniformly by passing coolant through a tube slightly larger than the rod to reduce thermal gradient. This paper also discusses issues related to beam distortion due to high repetition rate. In addition, energy, seeding technique, and beam quality evaluation of the engineering verification laser will be presented.
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Mulugeta Petros, Jirong Yu, Bo Trieu, Yingxin Bai, Paul Petzar, Upendra N. Singh, "300mJ injection seeded compact 2 micron coherent lidar transmitter", Proc. SPIE 6409, Lidar Remote Sensing for Environmental Monitoring VII, 64091A (12 December 2006); doi: 10.1117/12.694172; https://doi.org/10.1117/12.694172
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