A COMPACT OPTICAL HETERODYNE INTERFEROMETER BY OPTICAL INTEGRATION AND ITS APPLICATION

A compact high-resolution optical heterodyne interferometer combining a two-frequency light module and a minute optical system is described. The light module, which generates two independent frequencies of ligh t, is fabricated by proton exchange method on LiNbO3 substrate. We rep ort an experiment evaluating measurement accuracy using a micro-displa cement measurement system which incorporates this interferometer. Resu lts of the experiment with a standard thickness sample show high therm al stability with maximum measurement error of 1.8 nm at a temperature from 19 degrees C to 33 degrees C. The system was used to measure the hysteresis of a piezoelectric element for displacements of several nm , thereby making it possible to analyze the system quantitatively in p ractice.