A microresonator-based optical frequency comb pumped by a continuous-wave laser and regulated by an independent, injected tone is studied with focus on the locking range wherein the repetition rate can be controlled by the auxiliary laser. A generic phase synchronization model applicable to co- and counter-propagating injected tones and predicated on experimentally motivated assumptions is derived and investigated. The predictions of the model are compared with numerical integration of coupled mode equations describing frequency combs and with experimental data, demonstrating rich dynamics and excellent agreement despite simplicity. Applications of sideband injection in Kerr microcombs including to low phase noise radio frequency generation and the realization of dissipative discrete time crystals are discussed.
Optical microresonators possessing Kerr-type nonlinearity have emerged over the past decade as reliable and versatile sources of optical frequency combs, with varied applications including in the generation of low-phasenoise radio frequency (RF) signals, small-footprint precision timekeeping, and LiDAR. One of the key parameters affecting Kerr microcomb generation in different wavelength ranges is cavity modal dispersion. Dispersion effects such as avoided mode crossings (AMCs) have been shown to greatly limit mode-locked microcomb generation, especially when pumping in close proximity to such disruptions. We present numerical modeling and experimental evidence demonstrating that using an auxiliary laser pump can suppress the detrimental impact of near-pump AMCs. We also report, for the first time to our knowledge, the possibility of the breaking of characteristic soliton steps into two stable branches corresponding to different stable pulse trains arising from the interplay of dichromatic pumping and AMCs. These findings bear significance, particularly for the generation of frequency combs in larger resonators or at smaller wavelengths, such as the visible range, where the cavities become overmoded.
In this invited article, we report the experimental demonstration of the simultaneous coherent locking of two independent lasers with arbitrary multi-FSR (free spectral range) frequency separation to a Kerr microcomb soliton, resulting in the creation of synthetic microcomb soliton crystals. Each of the two pumps is self-injection- locked to its neighboring microcavity mode and acts as an arbiter linking the microcomb to the cavity. We show that the beating of the two pumps creates a manifest discrete symmetry and that certain microcomb states generated in this pumping scheme spontaneously break this symmetry, thereby realizing dissipative discrete time crystals. Apart from introducing a powerful platform leveraging advanced photonics for the creation and scientific exploration of various types of dissipative time crystals and their properties, our results constitute a decisive step towards the two-point locking of Kerr microcombs with moderate bandwidths much smaller than an octave which cannot be self-referenced through standard approaches such as the f - 2f technique.
A Kerr cavity soliton stabilization technique based on excitation by two continuous-wave pumps is proposed and theoretically and numerically investigated. Slow scanning of the second pump frequency near a comb harmonic of the soliton excited by the main pump locks the auxiliary pump to the soliton within a locking range. With the pumps locked to two frequency references, comb degrees of freedom will be stabilized. Evidence of stabilization and control of comb repetition rate using this technique is presented and the connection of duallypumped microcombs to "tiime crystals" is highlighted. The proposed approach extends to form a universal framework expounding soliton crystallization in microresonators supporting dispersive waves emitted by higherorder dispersion or mode anti-crossing. It can also obviate the exacting demand of octave-spanning combs for self-referencing.
Conference Committee Involvement (4)
Laser Resonators, Microresonators, and Beam Control XXVII
28 January 2025 | San Francisco, California, United States
Laser Resonators, Microresonators, and Beam Control XXVI
30 January 2024 | San Francisco, California, United States
Laser Resonators, Microresonators, and Beam Control XXV
31 January 2023 | San Francisco, California, United States
Laser Resonators, Microresonators, and Beam Control XXIV
24 January 2022 | San Francisco, California, United States
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