Theoretical investigation of tunable and broadband microwave frequency comb generation based on a current modulated semiconductor laser under optical injection

Based on a current modulated semiconductor laser (SL) subject to optical injection, tunable and broadband microwave frequency comb (MFC) generation is theoretically investigated. For a SL under only current modulation, a seed MFC with relatively narrow bandwidth can be generated. Then, an optical injection is introduced to improve the quality of seed MFC. Furthermore, the influences of operation parameters on the performance of MFC are also discussed. The numerical results show that after introducing optical injection with injection coefficient k = 1.8×10-4 and detuning frequency Δf = 6.0 GHz, the MFC bandwidth can be further increased by 15.6 GHz and the signal-to-noise ratio can be improved by more than 20 dB.