NASA's Goddard Space Flight Center is developing the Geoscience Laser Altimeter System (GLAS) employing a diode pumped, Q-switched, Nd:YAG laser operating at 40 Hz repetition rate. To meet the five-year mission lifetime goal, a single transmitter would accumulate over 6.3 billion shots. Cr⁴⁺:YAG is a promising candidate material for passively Q- switching the laser. Historically, the performance of saturable absorbers has degraded over long-duration usage. To measure the multi-billion shot performance of Cr⁴⁺:YAG, passively Q-switched GLAS-like oscillator was tested at an accelerated repetition rate of 500 Hz. The intracavity fluence was calculated to be approximately 2.5 J/cm². The laser was monitored autonomously for 165 days. There was no evidence of change in the material optical properties during the 7.2 billion shot test. All observed changes in laser operation could be attributed to pump laser diode aging. This is the first demonstration of multi-billion shot exposure testing of Cr⁴⁺:YAG in this pulse energy regime.

Date Published: 20 April 1998
PDF: 5 pages
Proc. SPIE 3244, Laser-Induced Damage in Optical Materials: 1997, (20 April 1998); doi: 10.1117/12.307020

Published in SPIE Proceedings Vol. 3244:
Laser-Induced Damage in Optical Materials: 1997
Gregory J. Exarhos; Arthur H. Guenther; Mark R. Kozlowski; M. J. Soileau, Editor(s)