Ultra-flat Optical Frequency Comb Generation Based on Phase Modulation with Simple Digital Driving Signal

A new scheme to generate flat and stable optical frequency combs (OFCs) with phase modulator and Gaussian band-stop filter is proposed. A periodic square-wave signal controlled with a bit sequence is used to drive the phase modulator to get an uneven OFC, and then a Gaussian band-stop filter is used to obtain an ultra-flat OFC. The comb spacing and flatness of the OFC can be adjusted by changing the period of the square-wave signal and the bandwidth of the Gaussian band-stop filter, respectively. The theoretical model of the proposed scheme is established, and the simulation results show that high quality OFCs with flatness lower than 0.5 dB and hundreds of spectral lines can be generated.