Optical frequency comb based on a distributed feedback semiconductor laser with direct injection current multi-frequency modulation

Abstract

Direct modulation of a semiconductor laser is a simple and low-cost method to generate compact optical frequency combs (OFCs). Herein, the use of direct injection current multi-frequency modulation (MFM) on a distributed feedback (DFB) semiconductor laser is proposed to generate OFCs. The number of modulation signals, frequency components, and modulation indices of the MFM signal are calculated according to the desired number of comb lines of the OFCs. The feasibility of this method was demonstrated by a series of experiments. OFCs composed of 9, 15, and 27 comb lines were generated with flatness values of 0.58 dB, 1.24 dB, and 2.53 dB, respectively, using a 1.58-μm DFB laser. The proposed method is easy to implement, it offers high flexibility in the selection of the repetition frequency. The proposed method is inexpensive and can improve the OFC quality with no laser-power loss.