Thermal and Nonlinear Dissipative-Soliton Dynamics in Kerr-Microresonator Frequency Combs

Abstract

We explore the dynamical response of dissipative Kerr solitons to changes in pump power and detuning and show how thermal and nonlinear processes couple these parameters to the frequency-comb degrees of freedom. Our experiments are enabled by a Pound-Drever-Hall (PDH) stabilization approach that provides on-demand, radio-frequency control of the frequency comb. PDH locking not only guides Kerr-soliton formation from a cold microresonator but opens a path to decouple the repetition and carrier-envelope-offset frequencies. In particular, we demonstrate phase stabilization of both Kerr-comb degrees of freedom to a fractional frequency precision below 10^{-16}, compatible with optical-time-keeping technology. Moreover, we investigate the fundamental role that residual laser-resonator detuning noise plays in the spectral purity of microwave generation with Kerr combs.

Dissipative Kerr solitons in optical microresonators

“…Photonicchip-based microresonators based on Si 3 N 4 are amenable to wafer-scale manufacturing and integration and, because of their higher nonlinearity (compared with that of crystals or silica), enable broadband DKS (72) with high repetition rates (>100 GHz). Although tuning into soliton states in integrated Si 3 N 4 microresonators has also been achieved with a slow laser-tuning method (73), the strong thermal effects have lead to the development of different methods, such as "power kicking" (74), fast tuning by use of heaters (19), and most recently, use of singlesideband modulator schemes (75). Using these techniques, DKSs have been generated in a wide variety of microresonators, ranging from bulk crystalline (9,45) and silica microdisks (17) and microspheres (76) to photonic chip-scale devices in Si and Si 3 N 4 (20, 77) and fiber cavities (21), under both CW and pulsed excitation (21).…”

“…In early work, this challenge was overcome by using an optimized laser scan (9). Since then, several techniques have been developed, from "power kicking" (74) to very fast laser modulation using single sideband modulators (75), as well as fast thermal on-chip tuning (19) and carrier injection (77). All developed techniques have in common that once the DKS state is reached, the thermal response of the cavity is dominated by the DKS, causing the system to be self-stabilized in the presence of a red-detuned (typically several linewidth) strong pump field.…”

Ultralow-noise photonic microwave synthesis using a soliton microcomb-based transfer oscillator

“…At higher offset frequencies, two noise bumps appear related to the characteristic double resonant response (S and C) of the resonator in the soliton regime 66 . In these resonant features, the transduction of the pump laser noise is enhanced 21 . Beyond 100 kHz offset, the contributions of various factors are more difficult to identify.…”

“…Direct soliton generation from an ultra-stable pump laser holds potential for compact and powerful optical-to-microwave dividers. Although self-referenced optical microcombs and clocks have been demonstrated [18][19][20] , optical frequency division for ultralow-noise microwave generation using such devices has not been demonstrated so far, mainly due to the complex crosstalk occurring between their two degrees of freedom 19,21 and the limited performance of the available actuators 17,22 .…”

Thermal decoherence and laser cooling of Kerr-microresonator solitons (Conference Presentation)

“…We generate Kerr solitons, using the fast-sweeping method 38,39 . A pump laser (New Focus Velocity) is modulated in the single-sideband, suppressed-carrier configuration by a voltage-controlled oscillator with 10-20 GHz output frequency.…”