Mitigating Fast Thermal Instability by Engineered Laser Sweep in AIN Soliton Microcomb Generation

Transient thermal instability represents a significant challenge in generating soliton microcombs. Fast laser sweep can be an efficient method to mitigate thermal instability, but it would require ultrahigh laser sweep rate for crystalline microresonators with fast thermal relaxation. Here, we engineer the laser sweep waveform to generate AIN-on-sapphire soliton microcombs with an intermediate sweep speed
$(< 30\text{GHz}/\mu \mathrm{s})$
. Two laser sweep methods with a backward + forward tuning or a two-step backward tuning added after the fast forward laser sweep are demonstrated to stabilize solitons.