Digitally Programmable Optical Frequency Combs With Binary Phase Distribution and Flat Envelope

We propose and experimentally demonstrate digitally programmable optical frequency combs (OFCs), featured by binary phase distribution and flat power envelope among comb lines for the first time. In the proposed simple generation scheme, a programmable optimized binary sequence is generated and applied to phase modulate a CW lightwave, creating an OFC with joint manipulation of both binary phase distribution and flat power envelope. Moreover, by digitally programing of the binary sequence, the generated OFC shows high tunability on comb spacing and comb-line number. In the experiments, tunable comb spacing of 20, 10, 5, 2 MHz and tunable comb-line number of 21, 51, 101 are demonstrated, while retaining excellent binary phase and flat power envelope. Such an agile joint manipulation of both phase and power paves a new way for promising phase-correlated applications of OFCs, such as the covert communications and weak signal detection.