The Laser Interferometer Gravitational-Wave Observatory uses highly stabilized continuous-wave solid-state lasers split down orthogonal arm cavities several kilometers long. By measuring the interference pattern of the recombined beams, the system can detect length changes smaller than a fraction of a proton radius. It represents one of the most extreme applications of vibration isolation, vacuum technology, and phase-sensitive optical metrology.
To hit the phase noise requirements for LIGO, they had to push the Nd:YAG seed lasers to unprecedented stability levels.
Related terms
Resonator
The arrangement of mirrors that sends light back and forth through the gain medium to build up laser oscillation.
CW
Continuous Wave: laser operation with a steady output beam rather than pulses.
Linewidth
The spectral width of a single-frequency laser's output, usually given in Hz, kHz or MHz at half maximum.