Kerr Microcavity Research Articles

Injection locking and breathing soliton microcomb generation dynamics of a nonlinear optical microcavity-laser diode butt-coupled system with pump power much higher than the parametric oscillation threshold

This paper mainly analyzes the injection locking mechanism of pump laser diode and the breathing microcavity optical frequency comb (microcomb) generation dynamics of the nonlinear optical Kerr microcavity-laser diode butt-coupled system with resonant Rayleigh backscattering feedback. The nonlinear dynamics is especially studied under the condition of the laser diode pump power much higher than the parametric oscillation threshold of the four-wave mixing microcomb in nonlinear Kerr microcavity. Further, we find that under the condition of high-power pumping, the exact mechanism for the system to produce the breathing microcomb is not due to the self-injection locking of the lasing frequency of the laser diode main pump mode, but a newly discovered microcavity resonant excitation mechanism through the pump mode modulation sideband (caused by microcavity Rayleigh backscattering feedback), which is closely related to the breathing characteristics of the generated soliton microcomb.

Dissipative discrete time crystals in a pump-modulated Kerr microcavity

Time crystals represent temporal analogues of the spatial self-ordering exhibited by atomic or molecular building blocks of solid-state crystals. The pursuit of discrete time crystals (DTCs) in periodically forced Floquet closed systems has revealed how they can evade thermalization and loss of temporal order. Recently, it has been shown that even with coupling to the ambient and its concomitant noise, some states maintain their time crystalline order, forming dissipative DTCs. Here, we introduce a scheme for the realization and state control of dissipative DTCs hinging on pumping a Kerr optical resonator with a phase-modulated continuous-wave laser. We show the possible symmetry breaking states possess temporal long-range order and analyze the phase noise of the accompanying signature radio frequency (RF) subharmonic. Besides offering a technique for generating high-spectral-purity RF signals, this versatile platform empowers controlled switching between various DTC states through accessible experimental knobs, hence facilitating the future study of DTC phase transitions.

Observation of gain spiking of optical frequency comb in a microcavity.

Optical frequency combs are crucial for both fundamental science and applications that demand a wide frequency range and ultra-high resolution. Recent advances in optical frequency combs based on the nonlinear Kerr effect in microcavities have opened up new opportunities with such compact platforms. Although optical frequency combs have previously been well studied in the steady state, some fundamental perspectives such as nonlinear phase modulation during comb generations are yet explored. Here we demonstrate transient nonlinear dynamics during the formation of optical frequency combs inside a Kerr microcavity. We show that gain spiking forms due to nonlinear phase modulation causing comb lines' self-detuning from nearby cavity resonances, which provides one key mechanism to stabilize optical frequency combs. Moreover, we have observed nonlinear beating by injecting an external probe to examine nonlinear cross-phase modulation between comb lines. These nonlinear dynamics reveal the hidden features of self-stabilization and cross modulation during transient comb generations, which may enable new applications in mode-locking comb and tunable comb generation in microcavities.

The LLE, pattern formation and a novel coherent source

The LLE was introduced in order to provide a paradigmatic model for spontaneous spatial pattern formation in the field of nonlinear optics. In the first part of this paper we describe in details its historical evolution. We underline, first of all, that the multimode instability of optical bistability represents an important precursor of the LLE. Next, we illustrate how the original LLE was conceived in order to describe pattern formation in the planes transverse with respect to the longitudinal direction of propagation of light in the nonlinear medium contained in the optical cavity. We emphasize, in particular, the crucial role of the low transmission limit (also called mean field limit or uniform field limit in the literature) in determining the simplicity of the equation. In discussing transverse pattern formation in the LLE, we underline incidentally the presence of very important quantum aspects related to squeezing of quantum fluctuations and to quantum imaging. We consider not only the case of global patterns but also localized structures (cavity solitons and their control). Then we turn to the temporal/longitudinal version of the LLE, formulated by Haelterman et al. [H. Haelterman, S. Trillo, S. Wabnitz, Opt. Commun. 91, 401 (1992)], and to its equivalence with the transverse LLE in 1D, discussing especially the phenomenon of temporal cavity solitons, their experimental observation and their control. Finally for the first part we turn to the very recent topic of broadband frequency combs, observed in a versatile multiwavelength coherent source (driven Kerr microcavity), which is raising a lot of interest and of research activities because of its very favourable physical characteristics, which support quite promising applicative perspectives. Kerr microcavities realize in an ideal manner the basic assumptions of the LLE, and the spontaneous formation of travelling patterns along the microcavity is the crucial mechanism which creates the combs and governs their features. Thus the LLE represents a case of spontaneous pattern formation which is immediately linked to a promising applicative avenue. The second part of the paper is devoted to the detailed derivation from the Maxwell-Bloch equations of the temporal/longitudinal LLE which was proposed by ourselves many years ago without providing a complete derivation. Such an equation is equivalent to the standard temporal/longitudinal version of the LLE in the case of anomalous dispersion. Our derivation elucidates in the best way the connection between the temporal/longitudinal version of the LLE and the multimode instability of optical bistability.

Dual-pump Kerr Micro-cavity Optical Frequency Comb with varying FSR spacing.

In this paper, we demonstrate a novel dual-pump approach to generate robust optical frequency comb with varying free spectral range (FSR) spacing in a CMOS-compatible high-Q micro-ring resonator (MRR). The frequency spacing of the comb can be tuned by an integer number FSR of the MRR freely in our dual-pump scheme. The dual pumps are self-oscillated in the laser cavity loop and their wavelengths can be tuned flexibly by programming the tunable filter embedded in the cavity. By tuning the pump wavelength, broadband OFC with the bandwidth of >180 nm and the frequency-spacing varying from 6 to 46-fold FSRs is realized at a low pump power. This approach could find potential and practical applications in many areas, such as optical metrology, optical communication, and signal processing systems, for its excellent flexibility and robustness.

All-optical diode based on dipole modes of Kerr microcavity in asymmetric L-shaped photonic crystal waveguide

A design of all-optical diode in L-shaped photonic crystal waveguide is proposed that uses the multistability of single nonlinear Kerr microcavity with two dipole modes. Asymmetry of the waveguide is achieved through different couplings of the dipole modes with the left and right legs of the waveguide. Using coupled mode theory we demonstrate an extremely high transmission contrast. The direction of optical diode transmission can be controlled by power or frequency of injected light. The theory agrees with the numerical solution of the Maxwell equations.