Multimode dynamics of a monolithically integrated, tunable, bidirectional, gain switched optical comb source

A three-sectioned, bidirectionally coupled, tunable, optical comb source is presented. The photonic integrated circuit (PIC) consists of a gain section, a slotted mirror section and a Fabry-Perot (FP) section. Optical frequency combs (OFCs) are produced by gain switching the FP section via a high power radio frequency (RF) signal. An investigation into the effect of the RF frequency on the quality of the OFC is performed. Multimode behavior is observed with OFCs produced in multiple modes as well as the overall degradation in the quality of the combs in each mode. A minimal extension multimode rate equation model is presented that reproduces the experimental results extremely well using experimentally determined values for numerical parameters. The appearance of multimode behavior is interpreted as relating to the modified relaxation oscillation frequency of the bidirectionally coupled system.