Master-oscillator power-amplifier meets LIGO requirements
Lightwave Electronics (Mountain View, CA) has shipped the first laser to be used in the Laser Interferometer Gravitational Wave Observatory (LIGO; Hanford, WA). The observatory was funded by the National Science Foundation to create two large interferometer systems, each 4 km long, for the first direct detection of gravity waves. The interferometers in LIGO require 10 W of frequency-stable, low-noise, high-beam-quality power. In response, engineers at Lightwave used four 1% Nd:YAG rods, each side-pumped by two nominal 20-W diode bars, to amplify the single-frequency output of a nonplanar ring oscillator (NPRO) from 700 mW to as high as 20 W.
The master oscillator-power amplifier configuration allowed the team to amplify the laser output as necessary while maintaining desirable NPRO characteristics, such as narrow linewidth, convenient frequency control, and low relative-intensity noise. The maximum output power of the system was 20 W for an input power of 520 mW.