High-Performance Microwave Frequency Comb Generation Using Optically Injected Semiconductor Laser with Dual-loop Optoelectronic Feedback

An approach to generating microwave frequency combs (MFCs) with superior performance is proposed and experimentally demonstrated based on an optically injected semiconductor laser (OISL). In this scheme, an OISL subject to a short-delay optoelectronic feedback loop is firstly applied to produce the initial MFC based on Fourier domain mode-locking, and a long-delay loop is added to improve the signal quality based on the self-injection-locking technique. In the experimental demonstration, a K-band MFC (18–26 GHz) with a line-spacing of 8.45 MHz has been obtained, and the comb contrast ratio is over 45 dB. In addition, the generated MFC exhibited superior performance in terms of spectral purity. Each comb component has a linewidth below 500 Hz and a phase noise below −90 dBc/Hz at 10kHz offset, demonstrating an excellent phase coherence between each comb component.