arXiv subjects

Alexey Belyanin

Publications and source records attributed to Alexey Belyanin.

At least 37 records · Page 2Linked to original sources

arXiv2022

The universal model of strong coupling at the nonlinear parametric resonance in open cavity-QED systems

Many molecular, quantum-dot, and optomechanical nanocavity-QED systems demonstrate strong nonlinear interactions between electrons, photons, and phonon (vibrational) modes. We show that such systems can be described by a universal model in the vicinity of the nonlinear parametric resonance involving all three degrees of freedom. We solve the nonperturbative quantum dynamics in the strong coupling regime of the nonlinear resonance, taking into account quantization, dissipation, and fluctuations of all fields. We find analytic solutions for quantum states in the rotating wave approximation which demonstrate tripartite quantum entanglement once the strong coupling regime is reached. We show how the strong coupling at the nonlinear resonance modifies photon emission and vibrational spectra, and how the observed spectra can be used to extract information about relaxation rates and the nonlinear coupling strength in specific systems.

quant-ph↗

arXiv2021

Generation of entangled photons via parametric down-conversion in semiconductor lasers and integrated quantum photonic systems

We propose and design a high-brightness, ultra-compact electrically pumped GaSb-based laser source of entangled photons generated by mode-matched intracavity parametric down-conversion of lasing modes. To describe the nonlinear mixing in highly dispersive and dissipative waveguides, we develop a nonperturbative quantum theory of parametric down-conversion of waveguide modes which takes into account the effects of modal dispersion, group and phase mismatch, propagation, dissipation, and coupling to noisy reservoirs. We extend our theory to the regime of quantized pump fields with a new approach based on the propagation equation for the state vector which solves the nonperturbative boundary-value problem of the parametric decay of a quantized single-photon pump mode and can be generalized to include the effects of dissipation and noise. Our formalism is applicable to a wide variety of three-wave mixing propagation problems. It provides convenient analytic expressions for interpreting experimental results and predicting the performance of monolithic quantum photonic systems.

quant-ph↗

arXiv2021

Quantum dynamics of open many-qubit systems strongly coupled to a quantized electromagnetic field in dissipative cavities

We study quantum dynamics of many-qubit systems strongly coupled to a quantized electromagnetic cavity mode, in the presence of decoherence and dissipation for both fermions and cavity photons. The analytic solutions are derived for a broad class of open quantum systems in Lindblad approximation. They include identical qubits, an ensemble of qubits with a broad distribution of transition frequencies, and multi-level electron systems. Compact analytic solutions for time-dependent quantum state amplitudes and observables become possible with the use of the stochastic equation of evolution for the state vector. We show that depending on the initial quantum state preparation, the systems can evolve into a rich variety of entangled states with destructive or constructive interference between the qubits. In particular, dissipation in a cavity can drive the system into the dark states completely decoupled from the cavity modes. We also find the regimes in which multi-electron systems with a broad distribution of transition frequencies couple to the quantized cavity field as a giant collective dipole.

quant-ph↗

arXiv2021

Self-starting Harmonic Comb Emission in THz Quantum Cascade Lasers

Harmonic comb state has proven to be emerging in quantum cascade lasers and promoted by an interplay between parametric gain and spatial hole burning. We report here on robust, pure, self-starting harmonic mode locking in Copper-based double-metal THz quantum cascade lasers. Different harmonic orders can be excited in the same laser cavity depending on the pumping condition and stable harmonic combs spanning more than 600 GHz bandwidth at 80 K are reported. Such devices can be RF injected and the free running coherence is assessed by means of self-mixing technique performed at 50 GHz. A theoretical model based on Maxwell-Bloch equations including an asymmetry in the gain profile is used to interpret the data.

physics.optics↗

arXiv2020

Dynamics and control of entangled electron-photon states in nanophotonic systems with time-variable parameters

We study the dynamics of strongly coupled nanophotonic systems with time-variable parameters. The approximate analytic solutions are obtained for a broad class of open quantum systems including a two-level fermion emitter strongly coupled to a multimode quantized electromagnetic field in a cavity with time-varying cavity resonances or the electron transition energy. The coupling of the fermion and photon subsystems to their dissipative reservoirs is included within the stochastic equation of evolution approach, which is equivalent to the Lindblad approximation in the master equation formalism. The analytic solutions for the quantum states and the observables are obtained under the approximation that the rate of parameter modulation and the amplitude of the frequency modulation are much smaller than the optical transition frequencies. At the same time, they can be arbitrary with respect to the generalized Rabi oscillations frequency which determines the coherent dynamics. Therefore, our analytic theory can be applied to an arbitrary modulation of the parameters, both slower and faster than the Rabi frequency, for complete control of the quantum state. In particular, we demonstrate protocols for switching on and off the entanglement between the fermionic and photonic degrees of freedom, swapping between the quantum states, and the decoupling of the fermionic qubit from the cavity field due to modulation-induced transparency.

quant-ph↗

arXiv2020

Relaxation operator for quasiparticles in a solid

Popular models of the phenomenological relaxation operators that are widely used in the master equation formalism for open condensed-matter systems have significant flaws ranging from limited applicability to violation of fundamental physical principles. We propose a relatively simple universal model of the relaxation operator which is free from these flaws, has a correct static limit, correct direct-current limit in a uniform electric field, includes both interband and intraband transitions, and is valid for an arbitrary dispersion of quasiparticles in a solid. We use the proposed operator to generalize the Lindhard formula and derive explicit expressions for the relaxation operator for Dirac materials with an unconventional energy spectrum of quasiparticles, such as graphene and Weyl semimetals. We compare the linear susceptibility spectra for graphene obtained with different relaxation models and show that the proposed relaxation operator leads to physically meaningful behavior of the susceptibility at low frequencies whereas the existing models become completely invalid.

cond-mat.mes-hall↗

arXiv2020

Generation and dynamics of entangled fermion-photon-phonon states in nanocavities

We develop the analytic theory describing the formation and evolution of entangled quantum states for a fermionic quantum emitter coupled to a quantized electromagnetic field in a nanocavity and quantized phonon or mechanical vibrational modes. The theory is applicable to a broad range of cavity quantum optomechanics problems and emerging research on plasmonic nanocavities coupled to single molecules and other quantum emitters. The optimal conditions for a tri-state entanglement are realized near the parametric resonances in a coupled system. The model includes decoherence effects due to coupling of the fermion, photon, and phonon subsystems to their dissipative reservoirs within the stochastic evolution approach, which is derived from the Heisenberg-Langevin formalism. Our theory provides analytic expressions for the time evolution of the quantum state and observables, and the emission spectra. The limit of a classical acoustic pumping and the interplay between parametric and standard one-photon resonances are analyzed.

quant-ph↗

arXiv2020

Harmonic frequency combs in quantum cascade lasers: time-domain and frequency-domain theory

Harmonic frequency combs, in which the lasing modes are separated by a period of tens of free spectral ranges from each other, have been recently discovered in quantum cascade lasers (QCLs). There is an ongoing debate how the harmonic combs can be formed and stable under continuous pumping. Here we reproduce the harmonic state of lasing in QCLs by space-time-domain numerical simulations and show that the corresponding optical wave has a frequency-modulated (FM) nature, with the fundamental beat note in the electron population being suppressed. To understand the physics behind the formation and stability of the harmonic state, we develop a frequency-domain linearized analytic theory which analyzes the stability of single mode lasing with respect to the harmonic state formation and the instabilities of the resulting harmonic state. Our analysis shows how the instability of a single lasing mode can result in the growth of harmonic side modes. The coupling between the two side modes leads to opposite gains for FM and amplitude-modulated (AM) waves, and the FM gain is enhanced as compared to the AM gain. The dependence of the sideband gain spectrum on group velocity dispersion is also studied. While the instability gain of a single lasing mode does not prove that the harmonic state can be self-starting, we analyze the sideband instability gain in the presence of three strong harmonic modes and demonstrate that the harmonic state can be stable and self-supported.

physics.optics↗

arXiv2020

Four-wave mixing in Weyl semimetals

Weyl semimetals (WSMs) have unusual optical response originated from unique topological properties of their bulk and surface electron states. Their third-order optical nonlinearity is expected to be very strong, especially at long wavelengths, due to linear dispersion and high Fermi velocity of three-dimensional Weyl fermions. Here we derive the third-order nonlinear optical conductivity of WSMs in the long-wavelength limit and calculate the intensity of the nonlinear four-wave mixing signal as it is transmitted through the WSM film or propagates away from the surface of the material in the reflection geometry. All results are analytic and show the scaling of the signal intensity with variation of all relevant parameters. The nonlinear generation efficiency turns out to be surprisingly high for a lossy material, of the order of several mW per W$^3$ of the incident pump power. Optimal conditions for maximizing the nonlinear signal are realized in the vicinity of bulk plasma resonance. This indicates that ultrathin WSM films of the order of skin depth in thickness could find applications in compact optoelectronic devices.

cond-mat.mes-hall↗

arXiv2020

Inverse Faraday effect in graphene and Weyl semimetals

We report systematic theoretical studies of the inverse Faraday effect in materials with massless Dirac fermions, both in two dimensions such as graphene and surface states in topological insulators, and in three dimensions such as Dirac and Weyl semimetals. Both semiclassical and quantum theories are presented, with dissipation and finite size effects included. We find that the magnitude of the effect can be much stronger in Dirac materials as compared to conventional semiconductors. Analytic expressions for the optically induced magnetization in the low temperature limit are obtained. Strong inverse Faraday effect in Dirac materials can be used for the optical control of magnetization, all-optical modulation, and optical isolation.

cond-mat.mes-hall↗

arXiv2019

Semiconductor ring laser frequency combs induced by phase turbulence

Semiconductor ring lasers are miniaturized devices that operate on clockwise and counterclockwise modes. These modes are not coupled in the absence of intracavity reflectors, which prevents the formation of a standing wave in the cavity and, consequently, of a population inversion grating. This should inhibit the onset of multimode emission driven by spatial hole burning. Here we show that, despite this notion, ring quantum cascade lasers inherently operate in phase-locked multimode states, that switch on and off as the pumping level is progressively increased. By rewriting the master equation of lasers with fast gain media in the form of the complex Ginzburg-Landau equation, we show that ring frequency combs stem from a phase instability---a phenomenon also known in superconductors and Bose-Einstein condensates. The instability is due to coupling of the amplitude and phase modulation of the optical field in a semiconductor laser, which plays the role of a Kerr nonlinearity, highlighting a connection between laser and microresonator frequency combs.

physics.optics↗

arXiv2019

Extreme anisotropy and gyrotropy of surface polaritons in Weyl semimetals

Weyl semimetals possess unique electrodynamic properties due to a combination of strongly anisotropic and gyrotropic bulk conductivity, surface conductivity, and surface dipole layer. We explore the potential of popular tip-enhanced optical spectroscopy techniques for studies of bulk and surface topological electron states in these materials. Anomalous dispersion, extreme anisotropy, and the optical Hall effect for surface polaritons launched by a nanotip provides information about Weyl node position and separation in the Brillouin zone, the value of the Fermi momentum, and the matrix elements of the optical transitions involving both bulk and surface electron states.

cond-mat.mes-hall↗

arXiv2019

Graphene Induced Large Shift of Surface Plasmon Resonances of Gold Films: Effective Medium Theory for Atomically Thin Materials

Despite successful modeling of graphene as a 0.34-nm thick optical film synthesized by exfoliation or chemical vapor deposition (CVD), graphene induced shift of surface plasmon resonance (SPR) of gold films has remained controversial. Here we report the resolution of this controversy by developing a clean CVD graphene transfer method and extending Maxwell-Garnet effective medium theory (EMT) to 2D materials. A SPR shift of 0.24 is obtained and it agrees well with 2D EMT in which wrinkled graphene is treated as a 3-nm graphene/air layered composite, in agreement with the average roughness measured by atomic force microscope. Because the anisotropic built-in boundary condition of 2D EMT is compatible with graphene's optical anisotropy, graphene can be modelled as a film thicker than 0.34-nm without changing its optical property; however, its actual roughness, i.e., effective thickness will significantly alter its response to strong out-of-plane fields, leading to a larger SPR shift.

physics.optics↗

arXiv2019

Laser radio transmitter

Since the days of Hertz, radio transmitters have evolved from rudimentary circuits emitting around 50 MHz to modern ubiquitous Wi-Fi devices operating at gigahertz radio bands. As wireless data traffic continues to increase there is a need for new communication technologies capable of high-frequency operation for high-speed data transfer. Here we give a proof of concept of a new compact radio frequency transmitter based on a semiconductor laser frequency comb. In this laser, the beating among the coherent modes oscillating inside the cavity generates a radio frequency current, which couples to the electrodes of the device. We show that redesigning the top contact of the laser allows one to exploit the internal oscillatory current to drive an integrated dipole antenna, which radiates into free space. In addition, direct modulation of the laser current permits encoding a signal in the radiated radio frequency carrier. Working in the opposite direction, the antenna can receive an external radio frequency signal, couple it to the active region and injection lock the laser. These results pave the way to new applications and functionality in optical frequency combs, such as wireless radio communication and wireless synchronization to a reference source.

physics.app-ph↗

arXiv2018

Second harmonic generation in graphene dressed by a strong terahertz field

We observe enhanced second-harmonic generation in monolayer graphene in the presence of an ultra-strong terahertz field pulse with a peak amplitude of 250 kV/cm. This is a strongly nonperturbative regime of light-matter interaction in which particles get accelerated to energies exceeding the initial Fermi energy of 0.2 eV over a timescale of a few femtoseconds. The second-harmonic current is generated as electrons drift through the region of momenta corresponding to interband transition resonance at an optical frequency. The resulting strongly asymmetric distortion of carrier distribution in momentum space gives rise to an enhanced electric-dipole nonlinear response at the second harmonic. We develop an approximate analytic theory of this effect which accurately predicts observed intensity and polarization of the second-harmonic signal.

cond-mat.mes-hall↗

arXiv2018

Optical properties and electromagnetic modes of Weyl semimetals

We present systematic theoretical studies of both bulk and surface electromagnetic eigenmodes, or polaritons, in Weyl semimetals. We derive the tensors of bulk and surface conductivity taking into account all possible combinations of the optical transitions involving bulk and surface electron states. We show how information about electronic structure of Weyl semimetals, such as position and separation of Weyl nodes, Fermi energy, and Fermi arc surface states, can be unambiguously extracted from measurements of the dispersion, transmission, reflection, and polarization of electromagnetic waves.

cond-mat.mes-hall↗

arXiv2018

Purcell enhancement of the parametric down-conversion in two-dimensional nonlinear materials

Ultracompact nonlinear optical devices utilizing two-dimensional (2D) materials and nanostructures are emerging as important elements of photonic circuits. Integration of the nonlinear material into a subwavelength cavity or waveguide leads to a strong Purcell enhancement of the nonlinear processes and compensates for a small interaction volume. The generic feature of such devices which makes them especially challenging for analysis is strong dissipation of both the nonlinear polarization and highly confined modes of a subwavelength cavity. Here we solve a quantum-electrodynamic problem of the spontaneous and stimulated parametric down-conversion in a nonlinear quasi-2D waveguide or cavity. We develop a rigorous Heisenberg-Langevin approach which includes dissipation and fluctuations in the electron ensemble and in the electromagnetic field of a cavity on equal footing. Within a relatively simple model, we take into account the nonlinear coupling of the quantized cavity modes, their interaction with a dissipative reservoir and the outside world, amplification of thermal noise and zero-point fluctuations of the electromagnetic field, and other relevant effects. We derive closed-form analytic results for relevant quantities such as the spontaneous parametric signal power and the threshold for parametric instability. We find a strong reduction in the parametric instability threshold for 2D nonlinear materials in a subwavelength cavity and provide a comparison with conventional nonlinear photonic devices.

physics.optics↗

arXiv2018

Difference frequency generation of surface plasmon-polaritons in Landau quantized graphene

We develop a rigorous quantum-mechanical theory of the nonlinear optical process of difference frequency generation of surface plasmon-polaritons in Landau-quantized graphene. Although forbidden in the electric-dipole approximation, the second-order susceptibility is surprisingly high, equivalent to the bulk magnitude above $10^{-3}$ m/V. We consider the graphene monolayer as a nonlinear optical component of a monolithic photonic chip with integrated pump fields. The nonlinear power conversion efficiency of the order of tens $μ$W/W$^2$ is predicted from structures of $10-100$ $μ$m size. We investigate a variety of waveguide configurations to identify the optimal geometry for maximum efficiency.

cond-mat.mes-hall↗