Laser power consumption of soliton formation in a bidirectional Kerr resonator

Laser sources power ultrafast data transmission, computing acceleration, access to ultra-high-speed signalling, and sensing applications such as chemical detection, distance measurements and pattern recognition. The ever-growing scale of these applications drives innovation in multiwavelength lasers for massively parallel processing. We report a nanophotonic Kerr-resonator circuit that converts the power of an input laser into a normal-dispersion soliton frequency comb at approaching unit efficiency. By coupling forward and backward propagation, we realize a bidirectional Kerr resonator that supports universal phase matching but also opens excess loss by double-sided emission. We therefore induce reflection of the resonator’s forward, external coupling port to favour backward propagation, resulting in efficient, unidirectional soliton formation. Coherent backscattering with nanophotonics provides the control to put arbitrary phase-matching and efficient laser power consumption on equal footing in Kerr resonators. In the overcoupled-resonator regime, we measure 65% conversion efficiency for a 40 mW input pump laser; the nonlinear circuit consumes 97% of the pump, generating the maximum possible comb power. Our work opens up high-efficiency soliton formation in integrated photonics, exploring how energy flows in nonlinear circuits and enabling laser sources for applications such as advanced transmission, computing, quantum sensing and artificial intelligence. Using a grating-based mode-splitting and reflector approach, a bidirectional chip-scale nanophotonic Kerr-resonator circuit that consumes 97% of the pump power to generate a soliton frequency comb at approaching unit efficiency with 65% conversion efficiency is reported.