FREQUENCY MEASURING APPARATUS AND FREQUENCY MEASUREMENT METHOD

摘要

PROBLEM TO BE SOLVED: To provide a frequency measuring apparatus for identifying a mode order of an optical comb with a simple configuration and measuring the absolute frequency of a laser beam from a measuring object, and a frequency measurement method.SOLUTION: A frequency measuring apparatus 1 comprises: an optical frequency comb device 2; a frequency-variable laser device 3 that is frequency-variable and has a mode transition frequency which changes an oscillation mode according to the frequency; an oscillation mode observation unit 6 for observing the oscillation mode of the frequency-variable laser device; and a beat frequency measurement unit 7 that measures a first beat frequency obtained by interference of output light of the optical frequency comb device and of the frequency-variable laser device and a second beat frequency obtained by interference of output light of a measuring object laser device and of the frequency-variable laser device. The frequency measuring apparatus 1 further identifies a mode order of the optical frequency comb device when the first beat frequency is measured on the basis of an observation result of the oscillation mode obtained by changing the frequency of the frequency-variable laser device, and measures an oscillation frequency of the measuring object laser device on the basis of the mode order, the first beat frequency and the second beat frequency.