Lifetime testing of a 355-nm, space-qualifiable laser

Abstract

A long-lived UV laser is an enabling technology for several high-priority, space-based lidar instruments. These include a next generation cloud and aerosol lidar that incorporates a UV channel, a direct detection 3-D wind lidar, and an ozone differential absorption lidar (DIAL) system. To advance the TRL of UV lasers we have designed and built a High Energy UV Demonstrator (HEUVD) that has increased output power and space-qualifiable packaging and that is mechanically robust, thermally-stable, and fully conductively cooled. Contamination control processes and optical coatings have been chosen that are compatible with multi-billion shot lifetimes. The diode pumped laser contains an essentially polymer free internal module that houses the third harmonic generator and beam expansion optics. When operated at 150 Hz the laser has demonstrated 275 mJ per pulse at 1064 nm, second harmonic conversion efficiencies of 70%, and third harmonic conversion efficiencies of 45%, thus meeting the 355 nm 100 mJ/pulse goal with margin. We have successfully completed a full power 532 nm life test, a half power (50 mJ/pulse) UV lifetest, and a full power (100 mJ/pulse @ 150 Hz) lifetest. These tests have validated the importance and success of our approach to contamination control for achieving a long-lived UV laser. They also resurfaced the need for the qualification of the pump laser diodes and more attention to the external optics in a UV lidar system.