Valery E. Lobanov

Microwave signal sources based on photonic integrated circuits offer exceptional compactness and robustness. Self-injection locking enables Kerr frequency comb generation in microring resonators, producing a low-phase-noise beat-note signal; however, the output comb power is typically low. Here, we use multifrequency self-injection locking by matching an integer ratio between the laser and microring mode grids, making the microwave signal power limited only by the available pump power, while the phase noise is still determined by the resonator Q-factor. Simultaneous locking to multiple adjacent microresonator modes separated by a free spectral range of 15 GHz is achieved. Phase noise reduction of the microwave beat-note signal is characterized, and the underlying physical mechanisms are analyzed. Our findings demonstrate significant potential for telecommunications and radio-over-fiber systems.

Self-injection locking of a diode laser frequency to a mode of a microresonator has proven to be an effective and robust technique of laser stabilization and Kerr microcomb generation. Here, we demonstrate and investigate a regime of multi-frequency self-injection locking (MF-SIL) of a single-frequency DFB diode laser. We show that in the normal group velocity dispersion (GVD) microresonator, MF-SIL enables the generation of different platicon-like multi-comb patterns. It is revealed that in this regime several narrow pump laser lines can appear and excite frequency combs independently, which leads to the generation of multi-comb patterns with a larger number of spectral components and enhanced pump-to-comb conversion efficiency. We study dynamics and conditions of multi-microcomb generation comparing it with single-platicon generation. These findings reveal new features of the laser–microresonator nonlinear interaction that are enabled by improvements in the fabrication of the photonic integrated circuits with high Q-factors.