Erwan Lucas

Universal dynamics and deterministic switching of dissipative Kerr solitons in optical microresonators

We discover a novel mechanism allowing for successive reduction of the number of dissipative Kerr solitons in optical microresonators. It is demonstrated that multiple and single soliton state can be deterministically accessed.

Self-referenced photonic chip soliton Kerr frequency comb

Self-referencing turns pulsed laser systems into self-referenced frequency combs. Such frequency combs allow counting of optical frequencies and have a wide range of applications. The required optical bandwidth to implement self-referencing is typically obtained via nonlinear broadening in optical fibers. Recent advances in the field of Kerr frequency combs have provided a path towards the development of compact frequency comb sources that provide broadband frequency combs, exhibit microwave repetition rates and that are compatible with on-chip photonic integration. These devices have the potential to significantly expand the use of frequency combs. Yet to date self-referencing of such Kerr frequency combs has only been attained by applying conventional, fiber based broadening techniques. Here we demonstrate external broadening-free self-referencing of a Kerr frequency comb. An optical spectrum that spans two-thirds of an octave is directly synthesized from a continuous wave laser-driven silicon nitride microresonator using temporal dissipative Kerr soliton formation and soliton Cherenkov radiation. Using this coherent bandwidth and two continuous wave transfer lasers in a 2f-3f self-referencing scheme, we are able to detect the offset frequency of the soliton Kerr frequency comb. By stabilizing the repetition rate to a radio frequency reference the self-referenced frequency comb is used to count and track the continuous wave pump laser’s frequency. This work demonstrates the principal ability of soliton Kerr frequency combs to provide microwave-to-optical clockworks on a chip.Self-referencing turns pulsed laser systems into self-referenced frequency combs. Such frequency combs allow counting of optical frequencies and have a wide range of applications. The required optical bandwidth to implement self-referencing is typically obtained via nonlinear broadening in optical fibers. Recent advances in the field of Kerr frequency combs have provided a path toward the development of compact frequency comb sources that provide broadband frequency combs, exhibit microwave repetition rates and are compatible with on-chip photonic integration. These devices have the potential to significantly expand the use of frequency combs. Yet to date, self-referencing of such Kerr frequency combs has only been attained by applying conventional, fiber-based broadening techniques. Here we demonstrate external broadening-free self-referencing of a Kerr frequency comb. An optical spectrum spanning two-thirds of an octave is directly synthesized from a continuous wave laser-driven silicon nitride microresonator using temporal dissipative Kerr soliton formation and soliton Cherenkov radiation. Using this coherent bandwidth and two continuous wave transfer lasers in a 2f–3f self-referencing scheme, we are able to detect the offset frequency of the soliton Kerr frequency comb. By stabilizing the repetition rate to a radio frequency reference, the self-referenced frequency comb is used to count and track the continuous wave pump laser’s frequency. This work demonstrates the principal ability of soliton Kerr frequency combs to provide microwave-to-optical clockworks on a chip.

Soliton dual frequency combs in crystalline microresonators

We present a novel compact dual-comb source based on a monolithic optical crystalline MgF2 multi-resonator stack. The coherent soliton combs generated in the two microresonators of the stack with the repetition rate of 12.1 GHz and difference of 1.62 MHz provided after heterodyning a 300 MHz wide radio frequency comb. An analogous system can be used for dual-comb spectroscopy, coherent LIDAR applications, and massively parallel optical communications.

All-optical stabilization of a soliton frequency comb in a crystalline microresonator

We demonstrate the all-optical stabilization of a low-noise temporal soliton based microresonator based optical frequency comb in a crystalline resonator via a new technique to control the repetition rate. This is accomplished by thermally heating the microresonator with an additional probe laser coupled to an auxiliary optical resonator mode. The carrier-envelope offset frequency is controlled by stabilizing the pump laser frequency to a reference optical frequency comb. We analyze the stabilization by performing an out-of-loop comparison and measure the overlapping Allan deviation. This all-optical stabilization technique can prove useful as an actuator for self-referenced microresonator frequency combs.

Detuning-dependent properties and dispersion-induced instabilities of temporal dissipative Kerr solitons in optical microresonators

Temporal-dissipative Kerr solitons are self-localized light pulses sustained in driven nonlinear optical resonators. Their realization in microresonators has enabled compact sources of coherent optical frequency combs as well as the study of dissipative solitons. A key parameter of their dynamics is the effective detuning of the pump laser to the thermally and Kerr-shifted cavity resonance. Together with the free spectral range and dispersion, it governs the soliton-pulse duration, as predicted by an approximate analytical solution of the Lugiato-Lefever equation. Yet a precise experimental verification of this relation has been lacking so far. Here, by measuring and controlling the effective detuning, we establish a way of stabilizing solitons in microresonators and demonstrate that the measured relation linking soliton width and detuning deviates by less than 1% from the approximate expression, validating its excellent predictive power. Furthermore, a detuning-dependent enhancement of specific comb lines is revealed due to linear couplings between mode families. They cause deviations from the predicted comb power evolution and induce a detuning-dependent soliton recoil that modifies the pulse repetition rate, explaining its unexpected dependence on laser detuning. Finally, we observe that detuning-dependent mode crossings can destabilize the soliton, leading to an unpredicted soliton breathing regime (oscillations of the pulse) that occurs in a normally stable regime. Our results test the approximate analytical solutions with an unprecedented degree of accuracy and provide insights into dissipative-soliton dynamics.

Universal dynamics and controlled switching of dissipative Kerr solitons in optical microresonators

We discover a novel mechanism allowing for successive reduction of the number of dissipative Kerr solitons in optical microresonators. It is demonstrated that multiple and single soliton state can be deterministically accessed.

Spatial multiplexing of soliton microcombs

Dual-comb interferometry utilizes two optical frequency combs to map the optical field’s spectrum to a radio-frequency signal without using moving parts, allowing improved speed and accuracy. However, the method is compounded by the complexity and demanding stability associated with operating multiple laser frequency combs. To overcome these challenges, we demonstrate simultaneous generation of multiple frequency combs from a single optical microresonator and a single continuous-wave laser. Similar to space-division multiplexing, we generate several dissipative Kerr soliton states—circulating solitonic pulses driven by a continuous-wave laser—in different spatial (or polarization) modes of a MgF2 microresonator. Up to three distinct combs are produced simultaneously, featuring excellent mutual coherence and substantial repetition rate differences, useful for fast acquisition and efficient rejection of soliton intermodulation products. Dual-comb spectroscopy with amplitude and phase retrieval, as well as optical sampling of a breathing soliton, is realized with the free-running system. Compatibility with photonic-integrated resonators could enable the deployment of dual- and triple-comb-based methods to applications where they remained impractical with current technology.Up to three distinct frequency combs are simultaneously generated from an optical microresonator and a continuous-wave laser, enabling the deployment of dual- and triple-comb-based methods to applications unachievable by current technologies.

Intermode Breather Solitons in Optical Microresonators

Dissipative solitons can be found in a variety of systems resulting from the double balance between dispersion and nonlinearity, as well as gain and loss. Recently, they have been observed to spontaneously form in Kerr nonlinear microresonators driven by a continuous wave laser, providing a compact source of coherent optical frequency combs. As optical microresonators are commonly multimode, intermode interactions, which give rise to avoided mode crossings, frequently occur and can alter the soliton properties. Recent works have shown that avoided mode crossings cause the soliton to acquire a single-mode dispersive wave, a recoil in the spectrum, or lead to soliton decay. Here, we show that avoided mode crossings can also trigger the formation of breather solitons, solitons that undergo a periodic evolution in their amplitude and duration. This new breather soliton, referred to as an intermode breather soliton, occurs within a laser detuning range where conventionally stationary (i.e., stable) dissipative Kerr solitons are expected. We experimentally demonstrate the phenomenon in two microresonator platforms (crystalline magnesium fluoride and photonic chip-based silicon nitride microresonators) and theoretically describe the dynamics based on a pair of coupled Lugiato-Lefever equations. We show that the breathing is associated with a periodic energy exchange between the soliton and a second optical mode family, a behavior that can be modeled by a response function acting on dissipative solitons described by the Lugiato-Lefever model. The observation of breathing dynamics in the conventionally stable soliton regime is relevant to applications in metrology such as low-noise microwave generation, frequency synthesis, or spectroscopy.

Soliton-based optical kerr frequency comb for low-noise microwave generation

Photonic generation of microwaves has shown record level low-noise performance, using optical frequency combs. We demonstrate direct low-noise microwaves with optical microresonator frequency combs via dissipative Kerr temporal soliton formation.

Low-noise microwave generation with optical microresonators

Optical frequency combs provide an equidistant grid of optical frequency components, enabling a wide array of diverse and new technologies [1]. One such application is photonic microwave generation where optical frequency combs provide unprecedented low-noise performance via optical frequency division [2]. Although providing excellent performance, it comes at the expense of size and complexity. In this work, we pursue a different route to provide both a compact and low-noise microwave source by direct microwave generation with microresonator based optical Kerr frequency combs (KFC) [3] that are formed via dissipative Kerr temporal solitons (DKS) in the microresonators [4]. A unique aspect of KFCs is their wide comb spacing (10 GHz-1THz) due to the small dimensions of the resonator. This enables a wide range of applications including optical communications, spectroscopy and direct generation of microwave signals. For this latter application, crystalline resonators are appealing over other microresonator platforms, as their low thermorefractive coefficient imply that the noise introduced by the resonator will be very low.