APPARATUS FOR OPTICAL HETERODYNE INTERFERENCE

摘要

PROBLEM TO BE SOLVED: To improve sensitivity of phase detection and make an apparatus economical. SOLUTION: This apparatus for optical heterodyne interference is provided with a Mach-Zehnder interferometer 30 having both a light branching means 14 for branching incident light into two and emitting two beams of light having different frequencies and an optical coupler 6 for emitting interference light by combining the two beams of light entering through different optical paths; a light receiver 8 for performing heterodyne detection on interference light; and a synchronous detector 15 for detecting the phase of its detection signals. The light branching means 14 comprises an ultrasonic generator 14b for generating ultrasonic waves of a frequency f1; an ultrasonic generator 14c for generating ultrasonic waves of a frequency f2; an acoustooptic frequency shifter (AOFS) 14d driven by the ultrasonic waves of the frequency f1; and an AOFS 14e driven by the ultrasonic waves of the frequency f2. A frequency difference between the emergent two beams of light is made equal to a frequency difference between the two ultrasonic waves, and the synchronous detector 15 is constituted of a lock-in amplifier. COPYRIGHT: (C)2007,JPO&INPIT