Generation of Tunable and Ultra-Broadband Microwave Frequency Combs Based on a Semiconductor Laser Subject to Pulse Injection From a Current Modulated Laser

We have experimentally demonstrated and characterized the generation of tunable and ultra-broadband microwave frequency combs (MFCs) based on a slave laser (SL) subject to regular pulse injection from a current modulated master laser (ML). Under modulation frequency f(m) = 1.2 GHz and modulation power P-m = 22 dBm, the current modulated ML is driven into a regular pulse state, and a seed MFC with 14.4 GHz bandwidth within a +/- 5 dB amplitude variation can be obtained. Such a seed MFC is then injected into the SL for producing final MFC with higher performances. For a fixed detuning frequency f(i) = 0 GHz and optimized injection power P-i = 2060 mu W, the bandwidth of the final MFC is increased to 33.6 GHz, and the single-sideband phase noises of all comb lines of the MFC within the bandwidth can be decreased to below -90.9 dBc/Hz@10kHz. Additionally, the influences of P-i and f(m) on the MFC bandwidth are also analyzed. The experimental results are in agreement with numerical simulations to a certain extent.