Grigory Lihachev

Mode Spectrum and Temporal Soliton Formation in Optical Microresonators

The formation of temporal dissipative solitons in optical microresonators enables compact, high-repetition rate sources of ultrashort pulses as well as low noise, broadband optical frequency combs with smooth spectral envelopes. Here we study the influence of the microresonator mode spectrum on temporal soliton formation in a crystalline MgF2 microresonator. While an overall anomalous group velocity dispersion is required, it is found that higher order dispersion can be tolerated as long as it does not dominate the resonators mode structure. Avoided mode crossings induced by linear mode coupling in the resonator mode spectrum are found to prevent soliton formation when affecting resonator modes close to the pump laser frequency. The experimental observations are in excellent agreement with numerical simulations based on the nonlinear coupled mode equations. The presented results provide for the first time design criteria for the generation of temporal solitons in optical microresonators.

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.

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.

Harmonization of chaos into a soliton in Kerr frequency combs

Dissipative Kerr solitons have paved the way to broadband and fully coherent optical frequency combs in microresonators. Here, we demonstrate numerically that slow frequency tuning of the pump laser in conjunction with phase or amplitude modulation corresponding to the free spectral range of the microresonator, provides reliable convergence of an initially excited chaotic comb state to a single dissipative Kerr soliton (DKS) state. The efficiency of this approach depends on both frequency tuning speed and modulation depth. The relevance of the proposed method is confirmed experimentally in a MgF2 microresonator.

Generation of platicons and frequency combs in optical microresonators with normal GVD by modulated pump

We demonstrate that flat-topped dissipative solitonic pulses, platicons, and corresponding frequency combs can be excited in optical microresonators with normal group velocity dispersion using either amplitude modulation of the pump or bichromatic pump. Soft excitation may occur in particular frequency range if modulation depth is large enough and modulation frequency is close to the free spectral range of the microresonator.

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.

Kerr soliton combs with regular multifrequency diode lasers

Kerr optical frequency combs in high-Q microresonators [1] are attracting growing interest [23], especially after mode-locking via dissipative Kerr solitons (DKS) has been demonstrated on a variety of platforms [3, 4]. Such combs are a promising source for compact applications due to its potential advantages of low power consumption and possibility of chip integration. A traditional approach to obtaining DKS in microresonators relies on narrow-linewidth tunable lasers for pumping. Independently the same type microresonators could be used for significant line narrowing of diode lasers exploiting resonant Rayleigh backscattering [5] for self-injection locking [6]. Kerr soliton frequency combs have also been demonstrated with self-injection locked diode lasers [7]. Previously for self-injection locking only single frequency stabilized diode lasers were used with either Bragg-grating [6] or distributed feedback configuration [7], having narrow linewidth comparable to the resonance linewidth of the high-Q microresonator. Surprisingly, we found that the initial stabilization is not required for soliton comb generation, and simpler but more powerful diode lasers may be used, and demonstrate a technique to stabilize, generate and control coherent low-noise soliton Kerr combs using commercial broad spectrum multi-frequency CW laser diodes, self-injection-locked to an ultra-high-Q crystalline whispering-gallery-mode microresonator. In this configuration the role of the microresonator is twofold: 1) it selects and narrows the linewidth of the laser via self-injection locking, and 2) soliton Kerr comb is generated in the microresonator. We manufactured a MgF2 resonator, 5 mm in diameter with computer controlled single-point diamond turning machine and polished it with diamond slurries, achieving Q > 109. For pumping, we used free-space laser diodes (Seminex, λ∼1535, 1550 and 1650 nm, spectrum width ∼10 nm, P∼200 mW) coupled to the resonator with a total internal reflection prism. Generation of self-injection locking soliton combs stable for hours (beat note linewidth <1kHz) was observed when the laser current was adjusted [Fig. 1]. By changing current it was possible to select the pumped mode of the resonator thus gradually changing the central frequency of the soliton by 10 nm. In several cases, we observed simultaneous excitation of two solitons with different central frequencies. In this case beat note spectrum demonstrated two narrow lines separated by ∼ 10 MHz distance, corresponding to FSR difference at central frequencies. The diode multimode spectrum (10 nm) was narrowed to single mode line with FWHM of only 5 kHz, comparable to the results achieved with self-injection-locked DFB lasers.

Kerr combs in microresonators: from chaos to solitons and from theory to experiment (Conference Presentation)

Kerr frequency combs in optical passive microresonators promise new breakthrough in photonics. Such combs result from multiple hyper-parametric four-wave mixing processes. The report presents the results of recent theoretical and experimental studies, leading to the development of compact and integrated coherent frequency comb sources.

Kerr frequency comb and brillouin lasing in BaF 2 whispering gallery mode resonator

We report the generation of Kerr frequency comb in normal group velocity dispersion (GVD) barium fluoride whispering gallery mode (WGM) resonator. Stimulated Brillouin scattering (SBS) with pump and Stokes beams in resonance with modes of the same high quality cavity is also observed. The overmoded resonator is pumped with 1550 nm c.w. light.