Use of a laser oscillator heterodyne interferometer as an optical sensor of microdisplacements

A laser oscillator heterodyne interferometer, used under single-frequency lasing conditions, was found to have a high sensitivity to changes in the path lengths in the interferometer arms amounting to a few optical wavelengths. A study was made of the mechanism which made it possible to vary widely the lasing frequency of the interferometer and its sensitivity to the phase shifts in the arms.