Oleg Egorov

Bright cavity polariton solitons.

The lower branch of the dispersion relation of exciton polaritons in semiconductor microcavities, operating in the strong-coupling regime, contains sections of both positive and negative curvature along one spatial direction. We show that this leads to the existence of stable one-dimensional bright microcavity solitons supported by the repulsive polariton nonlinearity. To achieve localization along the second transverse direction we propose to create a special soliton waveguide by changing the cavity detuning and hence the boundary of the soliton existence in such a way that the solitons are allowed only within the stripe of the desired width.

Nonlinear thermal effects in optical microspheres at different wavelength sweeping speeds.

Results of detailed experimental investigations of the power and sweeping speed dependent resonance bandwidth and resonance wavelength shift in microsphere resonators are presented. The experimental manifestations of the nonlinear effects for the different sweeping modes are considered and a possibility of separation between the Kerr and thermal nonlinearities is discussed. As it follows from the detailed comparison between theory and experiments, a single mode theoretical model, based on the mean field approximation, gives a satisfactory description of the experimental data only at small coupling powers and fast sweeping. For example, the values of Kerr nonlinearity, obtained through the fitting of the experimental data, are far from the expected, commonly used ones.

Discrete cavity solitons.

We derive evolution equations describing light propagation in an array of coupled-waveguide resonators and predict the existence of discrete cavity solitons. We identify stable, unstable, and oscillating solitons by varying the coupling strength between the anticontinuous and the continuous limit.

Observation of soliton molecules with independently evolving phase in a mode-locked fiber laser

We report the experimental generation of two-soliton molecules in an all-polarization-maintaining ytterbium-doped fiber laser operating in the normal dispersion regime. These molecules exhibit an independently evolving phase and are characterized by a regular spectral modulation pattern with a modulation depth of 80% measured as an averaged value. Moreover, the numerical modeling confirms that the limited modulation depth of the spectrum is caused by the evolution of the phase difference between the pulses.

Discrete Family of Dissipative Soliton Pairs in Mode-Locked Fiber Lasers

We numerically investigate the formation of soliton pairs (bound states) in mode-locked fiber ring lasers. In the distributed model (complex cubic-quintic Ginzburg-Landau equation) we observe a discrete family of soliton pairs with equidistantly increasing peak separation. This family was identified by two alternative numerical schemes and the bound state instability was disclosed by a linear stability analysis. Moreover, similar families of unstable bound state solutions have been found in a more realistic lumped laser model with an idealized saturable absorber (instantaneous response). We show that a stabilization of these bound states can be achieved when the finite relaxation time of the saturable absorber is taken into account. The domain of stability can be controlled by varying this relaxation time.

How does an inclined holding beam affect discrete modulational instability and solitons in nonlinear cavities

We study light propagation in arrays of weakly coupled nonlinear cavities driven by an inclined holding beam.We show analytically that both discreteness and inclination of the driving field can dramatically change the conditions for modulational instability in discrete nonlinear systems. We find numerically the families of resting and moving dissipative solitons for an arbitrary inclination angle of the driving field, both in the discrete and a quasi-continuous limits. We analyze a crossover between resting and moving cavity solitons, and also observe novel features in the soliton collision.

Subdiffractive discrete cavity solitons

We describe what we believe to be novel types of discrete cavity solitons in nonlinear waveguide arrays that are driven by an external holding beam. We demonstrate that a holding beam with a definite inclination drives the system in a subdiffractive regime and allows the formation of stable discrete cavity solitons. We predict the existence of both bright and dark moving midband discrete cavity solitons for an identical set of system parameters for both focusing and defocusing Kerr nonlinearities.

Creation and Manipulation of Stable Dark Solitons and Vortices in Microcavity Polariton Condensates

Solitons and vortices obtain widespread attention in different physical systems as they offer potential use in information storage, processing, and communication. In exciton-polariton condensates in semiconductor microcavities, solitons and vortices can be created optically. However, dark solitons are unstable and vortices cannot be spatially controlled. In the present work we demonstrate the existence of stable dark solitons and vortices under nonresonant incoherent excitation of a polariton condensate with a simple spatially periodic pump. In one dimension, we show that an additional coherent light pulse can be used to create or destroy a dark soliton in a controlled manner. In two dimensions we demonstrate that a coherent light beam can be used to move a vortex to a specific position on the lattice or be set into motion by simply switching the periodic pump structure from two-dimensional (lattice) to one-dimensional (stripes). Our theoretical results open up exciting possibilities for optical on-demand generation and control of dark solitons and vortices in polariton condensates.

Bistability in microcavities with incoherent optical or electrical excitation

Introduction.—Bistability and hysteresis are fundamental properties of resonant optical nonlinear systems [1] with applications in optical memory elements and transistors. Optical nonlinearity ultimately relies on the coupling of light to electronic degrees of freedom, which mediate effective interactions between photons. With an ever-growing effort devoted to the enhancement of light-matter coupling, high nonlinearity allows bistability to be routinely observed in a variety of systems. One example is the strong light-matter coupling in high quality factor semiconductor microcavities containing quantum well excitons [2, 3]. The resulting excitonpolaritons are known to exhibit bistability, when driven resonantly and coherently [4–6], i.e., with a pumping laser tuned to the energy of the exciton-polariton quasiparticle. This allows a variety of related effects to occur, including driven superfluidity [7], the suppression of disorder [8] and the formation of various structures – spin patterns [9–11], solitons [12–16], and vortex lattices [17]. Controlled switching has been observed in multi-mode systems, based on the overlapping of states with different energies and wavevectors [18] or the spin degree of freedom [19–21]. In addition, bistability underpins theoretical schemes for electro-optic [23] and all-optical circuits [24, 25]. An important step towards low-threshold polaritonic lasing and electrically controlled integrated polaritonic circuits is condensation of electrically injected polaritons, which was recently observed [22]. The practical potential of electrically injected devices [26–29] relies on the compatibility of physical mechanisms controlling bistability with incoherent, non-resonant excitation. However, all of the polaritonic devices based on bistability demonstrated to date require a coherent optical excitation, implying that they must be coupled with a laser light that is resonant or near-resonant with the exciton-polariton state. In this Letter, we propose a mechanism of optical bista

Collective state transitions of exciton-polaritons loaded into a periodic potential

O.A.E. acknowledges financial support by the Deutsche Forschungsgemeinschaft (DFG project EG344/2-1) and by the EU project (FP7, PIRSES-GA-2013-612600) LIMACONA. I.G.S. acknowledges support from the Academy of Finland through its Centre of Excellence Programs (Projects No. 250280 and No. 251748); Government of Russian Federation (project MK-5903.2016.2); and Dynasty Foundation. E.E., T.G., I.G.S., and E.A.O. acknowledge support by the Australian Research Council.