arXiv subjects

Egor S. Vyatkin

Publications and source records attributed to Egor S. Vyatkin.

6 recordsLinked to original sources

arXiv2026

Twist tunable resonances in photonic bilayer for second harmonic generation

Moiré structure emerging in photonic bilayers stacked with a twist enables the controllable frequency selective resonant response. Here, we employ twist tunable resonances to boost second harmonic generation (SHG) at a desired frequency in twisted photonic bilayers integrated with two-dimensional nonlinear crystals. We develop an analytical theory relating the resonance frequencies and the SHG enhancement factor to the material parameters of the dielectric layers and the twist angle. The theory reveals a critical twist angle separating two distinct regimes of photonic bilayer operation: with open and closed moiré diffraction channels. Above the critical angle, the photon leakage from the guided mode is suppressed and the SHG enhancement factor rises by orders of magnitude. The paper offers a compact route to nonlinear conversion in moiré photonic structures efficient and tunable over a wide spectral range.

physics.optics↗

arXiv2025

Resonant enhancement of second harmonic generation in 2D nonlinear crystal integrated with meta-waveguide: analytical vs numerical approaches

We present an analytical theory of second harmonic generation (SHG) in hybrid structures combining a nonlinear 2D crystal with a dielectric metasurface waveguide. The theory describes the excitation spectrum and enhancement of SHG at both leaky mode and quasi-bound state in the continuum (quasi-BIC) resonances in terms of the material parameters. For low-loss systems, the SHG efficiency at leaky resonances is determined by their radiative broadening, governed by the relevant Fourier harmonics of the metasurface polarizability, whereas the SHG enhancement at quasi-BIC resonances is ultimately limited by inhomogeneous broadening and absorption in the system. We also describe the emergence and polarization properties of second harmonic diffracted beams. These beams appear even if both the 2D crystal and the meta-waveguide are centrosymmetric owing to the nonlocal mechanism of SHG. The developed framework provides a systematic theoretical basis for optimizing the resonant nonlinear frequency conversion in hybrid 2D-material-metasurface platforms and identifies the fundamental limitations of the SHG efficiency.

physics.optics↗

arXiv2024

Emergent spin and orbital angular momentum of light in twisted photonic bilayer

We demonstrate that the optical response of twisted photonic bilayers, photonic counterparts of van der Waals structures, is sensitive to both spin angular momentum (SAM) and orbital angular momentum (OAM) of light. A beam of unpolarized light with zero angular momentum acquires SAM in transmission and OAM in reflection. The developed analytical theory and numerical calculations show that the SAM and OAM arise from distinct microscopic mechanisms and depend differently on the interlayer distance. The predicted phenomena do not require light absorption and are caused by the photon-helicity-dependent light diffraction by the moiré pattern, which inevitably occurs in the twisted structure, and the SAM-OAM conversion processes. We also reveal strong SAM and OAM in the moiré-diffracted beams. Our findings uncover a profound connection between the emergent SAM and OAM in twisted photonic systems offering new possibilities for angular-momentum-resolved light-matter interactions.

physics.optics↗

arXiv2024

Nonlinear dynamical Casimir effect and Unruh entanglement in waveguide QED with parametrically modulated coupling

We study theoretically an array of two-level qubits moving relative to a one-dimensional waveguide. This motion can be implemented mechanically or simulated via the modulation of the couplings between the qubits and the waveguide. When the frequency of this motion approaches twice the qubit resonance frequency, it induces parametric generation of photons and excitation of the qubits. The proposed quantum optomechanical system offers a plethora of possibilities for exploring various quantum electrodynamics phenomena. However, their theoretical analysis is challenging due to the presence of quantum nonlinearity, a continuum of propagating photonic modes, and the excitation of strongly nonequilibrium qubit states, which make many conventional analytical tools inapplicable. To address these challenges, we develop a comprehensive general theoretical framework that incorporates both perturbative diagrammatic techniques and a rigorous master-equation approach. Our calculations reveal several intriguing effects, including the directional dynamical Casimir effect, where momenta of emitted photon pairs are correlated, and the waveguide-mediated collective Unruh effect, where motion drives the qubits to a nontrivial steady state that can be entangled and exhibit phase transitions. Additionally, we examine the radiation back-action on the qubit motion, which becomes particularly pronounced when subradiant modes in the qubit array are excited. The back-action can significantly alter the mechanical spectra, potentially leading to the formation of hybrid phonon-biphoton modes.

quant-ph↗

arXiv2024

Resonant Parametric Photon Generation in Waveguide-coupled Quantum Emitter Arrays

We have developed a theory of parametric photon generation in the waveguides coupled to arrays of quantum emitters with temporally modulated resonance frequencies. Such generation can be interpreted as a dynamical Casimir effect. We demonstrate numerically and analytically how the emission directionality and photon-photon correlations can be controlled by the phases of the modulation. The emission spectrum is shown to be strongly dependent on the anharmonicity of the emitter potential. Single- and double-excited state resonances have been identified in the emission spectrum.

quant-ph↗

arXiv2021

Optomechanical amplification driven by interference of phonon-exciton and phonon-photon couplings

We study theoretically optomechanical damping and amplification spectra for vibrations interacting with excitonic polaritons in a zero-dimensional microcavity. We demonstrate, that the spectra strongly depend on the ratio of the exciton-phonon and the photon-phonon coupling constants. The interference between these couplings enables a situation when optomechanical gain exists either only for a lower polaritonic resonance or only for an upper polaritonic resonance. Our results provide insight in the optomechanical interactions in various multi-mode systems, where several resonant oscillators, such as photons, plasmons, or excitons are coupled to the same vibration mode.

cond-mat.mes-hall↗