Universal Kerr-Thermal Dynamics of Self-Injection-Locked Microresonator Dark Pulses

Area of Science:

• Photonics
• Nonlinear Optics
• Integrated Photonics

Background:

• Microcombs are miniaturized optical frequency combs generated in microresonators.
• Hybrid integration of semiconductor lasers and microresonators offers compact microcomb solutions.
• Existing linear self-injection locking theory inadequately describes nonlinear processes like dark-pulse formation.

Purpose of the Study:

• To investigate the Kerr-thermal dynamics of a semiconductor laser self-injection locked to an integrated silicon nitride microresonator.
• To develop a theoretical model for dark-pulse formation in such hybrid systems.
• To demonstrate an application of this phenomenon for low-noise photonic microwave generation.

Main Methods:

• Theoretical investigation of Kerr-thermal dynamics.
• Numerical simulations of laser-microresonator coupling.
• Experimental validation using a hybrid integrated system.

Main Results:

• Unveiled universal dark-pulse formation and discrete switching behavior.
• Established a theoretical model accounting for mutual coupling, Kerr nonlinearity, and photothermal effects.
• Achieved low-noise photonic microwave generation with 23.5 dB phase noise purification.

Conclusions:

• The study provides critical insights into pulse formation in laser-microresonator hybrid systems.
• The developed model accurately describes the observed nonlinear phenomena.
• This work enables all-passive, photonic-chip-based microwave oscillators with high spectral purity.