Koichiro MIYAGI, Masaya NANAMI, Isao KOBAYASHI and Akira TANIGUCHI

Research Laboratory, ANRITSU Corporation, 1800, Onna, Atsugi, Kanagawa, 243 Japan

(Received July 10, 1996; Accepted September 9, 1996)

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 light, is fabricated by proton exchange method on LiNbO₃ substrate. We report an experiment evaluating measurement accuracy using a micro-displacement measurement system which incorporates this interferometer. Results of the experiment with a standard thickness sample show high thermal stability with maximum measurement error of 1.8 nm at a temperature from 19°C to 33°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 practice.

Key words : heterodyne interferometer, optical frequency shifter, SAW, proton exchange