3.17-THz frequency-difference measurement between lasers using two optical frequency combs

In order to increase the signal-to-noise ratio in the measurement of frequency-difference between two lasers by using an optical frequency comb generator (OFC-G), two laser beams were combined into the OFC-G. Then many sidebands that contribute to the beat signal generation were generated. We observed the spectrum of the beat signal with a signal-to-noise ratio of 30 dB when the frequency-difference between two lasers was 3.17 THz.