[OPTICAL REVIEW Vol. 8, No. 1 (2001) 37-42]

Phase-Drift-Suppression in Heterodyne Detection Using Coherent Light Source

Manabu SATO,1 Yoshifumi IKEDA,1 Masakazu ENDO,1 Shinji FUKUDA1 and Naohiro TANNO1,2

1Graduate Program of Human Sensing and Functional Sensor Engineering, Graduate School of Science and Engineering, Yamagata University, Yonezawa, Yamagata, 992-8510 Japan, 2Japan Science and Technology Corporation, Regional Joint Research Project of Yamagata Prefecture, Yamagata, 990-2473 Japan

(Received June 8, 2000; Accepted September 30, 2000)

The validity of the phase-drift-suppression method (PDSM) using coherent light sources of a single-mode laser diode (LD) or multimode Nd:YAG laser has been experimentally shown. PDSM can enhance the stability of an output signal in heterodyne detection using higher order harmonics. In the Michelson interferometer, the fundamental and second harmonics in heterodyne beat signals were detected by two lock-in amplifiers, and the computed signal intensity (CSI) was obtained in the computer as an output signal. Relations between the stability of CSI and modulation indexes in sinusoidal phase modulations were measured. The CSI stability was enhanced about twice by PDSM using a single-mode laser diode, and from 4 times to 9 times using a multimode laser.

Key words : heterodyne beat signal, stabilization, harmonics, phase drift, coherent light