Measurement of phase fluctuations in a HF chemical laser beam

A new phase detector, which uses an acousto-optic modulation and optical heterodyne technique, has been developed. The minimum detectable phase difference is 4 °, with a temporal response of 10 μsec and a spatial resolution of 0.14 mm. This phase detector was used to measure fluctuations in the wave front of a 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.