Experimental study of optical frequency comb generation in gain-switching vertical-cavity surface-emitting laser driven by various modulation signals under optical injection

In this work, we have experimentally investigated the generation of broadband optical frequency comb (OFC) based on a gain-switching vertical-cavity surface- emitting laser (VCSEL) driven by different modulation signals (including triangular-current, sinusoidal-current and square-current) under optical injection. For such a system, various modulation signals are first used to drive the VCSEL into the gain-switching state, and then an external optical injection is further introduced into the gain-switching VCSEL to generate broadband OFC. The experiment results show that the OFC output from the square-current modulated VCSEL subject to optical injection has better performance compared to other two modulation signals. Driven by square signal with matched operation parameters, a high quality OFC can be acquired, with stable comb lines, high coherence, wide bandwidth of 72.0 GHz within 10 dB amplitude variation and low single sideband phase noise at the fundamental frequency below -113.3 dBc/Hz @ 10 kHz.