Reliable optical pump architecture for highly coherent lasers used in space metrology applications

Laser-based metrology has been identified as an enabling technology in the deployment of large, space-borne observatories, where nanometer-level knowledge of fiducial displacement drives overall system performance. In particular, Nd:YAG NPRO (non-planar ring oscillator) based lasers have received considerable attention in this application because of their inherent high coherence at wavelengths of interest (1064 and 1319nm). However, decade long, NPRO based, space missions are limited by typical 800nm-band pump laser diode wear-out and random failure rates. Therefore, multi-hundred milliwatts NPRO power over prolonged mission lifetimes requires innovative pump architectures. In this paper we present a pump architecture capable of supporting continuous NPRO operation over 5.5yrs at 300mW. The proposed pump architecture relies on a robust all optical fiber coupler that executes the pump beam combining function necessary to support the stated mission power and operating conditions. This coupler has been demonstrated to withstand the exacting environmental requirements placed by a space mission, such as SIM Lite.