20-W diode-pumped single-frequency Nd:YAG MOPA for the Laser Interferometer Gravitational Wave Observatory

We amplified the 700-mW single-frequency output from a nonplanar ring oscillator (NPRO) to produce up to 20 W using a double-pass diode-pumped rod amplifier. The laser maintains all the desirable characteristics of the NPRO such as narrow linewidth, convenient frequency control, and low relative intensity noise. Power drift, beam quality, and beam stability meet the demanding requirements for use in the LIGO Laser Interferometer Gravitational Wave Observatory.