A robust program-controlled microcomb source

Abstract

Optical frequency combs generated by nonlinear effects in microcavities have played an important role in many fields due to their precise frequency characteristics. However, constrained by the strict requirement of the balance between the nonlinear effect and the dispersion and the thermal instability when reaching the soliton states, the current microcomb sources are mostly heavily reliant on manual tests and are environmentally sensitive. We present a compact FPGA-based microcomb source. Thresholds of the average and variance of the transmitted signal are determined from sampled spectrum and used for the distinguishment of the intra-cavity state. Generation of arbitrary optical state and self-recovery under external disturbance is achieved. Furthermore, feedback locking is applied to the laser frequency via the output power, which improves the immunity to temperature changes. The presented source shows great stability which can promote future applications of microcombs.