Dynamic tuning of soliton microcomb repetition rate without direct cavity actuation

Optical frequency combs (OFCs) bridge the optical and microwave domains through their repetition rate. While stable repetition rates serve metrology, many applications require dynamic tuning. OFCs are typically not directly actuated but instead controlled indirectly through modifications of the cavity properties housing the OFC. On-chip physical resonator actuation, however, requires complex heterogeneous integration of piezoelectric, electro-optic, or thermal components, which can be challenging for foundry-based mass-fabrication. Here, we present an all-optical alternative to directly modulate an integrated microcomb’s repetition rate using Kerr-induced synchronization (KIS) with a modulated reference laser capturing one comb tooth, without actuating or perturbing the microring resonator. The repetition rate, determined by the main and reference pump frequencies, responds linearly to the reference frequency modulation according to optical frequency division. This enables arbitrary waveform coherent transfer to the OFC repetition rate using only a foundry-fabricated, passive silicon nitride microring resonator. This simplified approach will facilitate tunable microwave synthesis, spectroscopy, and ranging applications.