Program-Controlled Single Soliton Generation Driven by the Thermal-Compensated Avoided Mode Crossing

Single soliton microcombs enable the chip-scaled comb source with an extremely high repetition rate suitable for many applications. However, it is challenging to deterministically generate a single soliton due to the thermal effect and the stochastic soliton formation. Meanwhile, mode coupling induced avoided mode crossings (AMXs) also affect the soliton generation. Here, we analyze the thermal compensation effect of an auxiliary laser on the single soliton generation based on a Si ₃ N ₄ micro-resonator with weak AMXs. Both simulation and experiments demonstrate that only in a proper blue-detuned range of the auxiliary laser can achieve the high-probable single soliton generation. Based on the above observation, we present a program-controlled scheme for reliable single soliton generation based on the red-detuned pump entrance forward tuning method. A single soliton is successfully generated in 100 trials with a 100% success rate. We also stabilize the single soliton generation by pump back tuning and feedback control of the auxiliary wavelength and achieve more than 5 hours of the soliton duration time in the experiments.