Eye-Safe, UV BackScatter Lidar for Detection of Sub-Visual Cirrus

Improved measurements and understanding of cirrus clouds is essential for the accurate modeling of climate change and, in particular, for feedback effects that respond (positively or negatively) to greenhouse-gas global warming. Unfortunately, the reliable autonomous detection of sub-visual cirrus clouds is limited by the poor signal-to-noise ratio of existing micropulse lidars. Backscatter lidar detection in the UV presents an attractive solution for this problem ¿ because molecular scattering increases with shorter wavelength and eye-safety constraints are greatly relaxed ¿ permitting much higher laser output power. This project will develop a complete UV lidar system, which utilizes an advanced diode pumped solid-state laser (Yb:S-FAP), enabling a 50X improvement in the signal-to-noise ratio compared to micropulse lidars. By the end of Phase I, the required laser performance (50 mJ/pulse at 349 nm and 100 Hz repetition rate) will be demonstrated in a working UV laser breadboard. The laser demonstration will leverage an existing Yb:S-FAP system by efficiently converting the 1047 nm output of the Yb:S-FAP laser to the third harmonic at 349 nm. Commercial Applications and Other Benefits as described by the Applicant: Diode pumped solid state lasers are used extensively in materials processing and other high value commercial applications. However, to date, diode pumped solid-state lasers have not achieved significant market penetration in the high-pulse-energy (> 100 mJ) laser markets, which currently are dominated by excimer and lamp pumped solid-state lasers. Although diode-pumped solid-state lasers have significant performance and operational advantages, their use has been limited due to the high cost of the diode laser pump sources. The technical approach of this project takes advantage of the comparatively long storage lifetime of Yb:S-FAP, enabling a high-pulse-energy, diode-pumped, solid-state laser application at greatly reduced cost (by a factor of 4 to 5 compared with a Nd:YAG laser).