Measurement of phase fluctuations in a HF chemical laser beam

A phase detector which uses an acousto-optic modulation and optical heterodyne technique was developed. The minimum detectable phase difference is 4 deg, with a temporal response of 10 micron sec and a spatial resolution of 0.14 mm. The phase detector was used to measure fluctuations in the wavefront of CW HF chemical laser beam caused by mechanical vibration, medium turbulence, and gain variation. Potential applications are laser beam quality measurement, beam steering measurement, and sensing for an active resonator.