Super-heterodyne Interferomter for Length-Measurment Using the Beat Signal of Laser Diodes and the Optical Frequency Comb

摘要

We proposed a super-heterodyne interference system for absolute length measurements using multiple laser diodes and an optical frequency comb as the light sources. The frequencies of the laser diodes will be phase-locked on the different modes of the optical comb with different offset frequencies for the method of excess fractions. The measurement range can be changed when frequencies of the laser diodes are phase locked on different modes of the optical comb, and the step-by-step measurement can be realized. The preliminary experiments were done to compare the measurement stability of two optical combs and a laser diode using a heterodyne interference system. The result shows that the measurement stabilities in 50 s of optical comb and laser diode were similar. The measurement standard deviation decreases to several tens of nanometres when the time constant of lock-in amplifier increases to 10 s.