arXiv subjects

Alexander V. Uskov

Publications and source records attributed to Alexander V. Uskov.

At least 19 recordsLinked to original sources

arXiv2025

Reflection and refraction properties of laser-driven 2D quantum well: Analogy with Photonic Time Crystal

It has been demonstrated that a quantum well with optically excited, homogeneous oscillations of a two-dimensional (2D) electron plasma behaves as a photonic time crystal when it scatters an obliquely incident, weak probe electromagnetic wave. The hydrodynamic approximation is used to describe self-consistently the interaction between the probe wave and the 2D plasma. Such a quantum well becomes a polychromatic source and to the first order in perturbation reflected and transmitted radiation reveals as non-shifted in frequency principal components along with up- and down-shifted in frequency satellites. The downshifted satellites are backward propagating when the frequency of the probe wave is less than that of the plasma oscillations. We found the condition when the downshifted components are the surface waves. For the s-polarized probe wave, we found that the laser-driven quantum well can support propagation of TE surface wave, which would not normally be permitted to propagate freely. The amplitudes of the reflected and transmitted components are determined for the principal components and the up- and down-shifted satellites.

physics.optics↗

arXiv2025

Increased output of superradiant light-emitting diodes due to population fluctuations

The quantum nonlinear Maxwell-Bloch equations for a single-mode laser with a two-level active medium are solved in the LED regime without adiabatic elimination of the medium polarization, when the population fluctuation spectrum is much narrower than the radiation and polarization spectra. It is shown that population fluctuations significantly increase the output power and collective Rabi splitting of a superradiant LED.

quant-ph↗

arXiv2024

Population fluctuation mechanism of the super-thermal photon statistic of LEDs with collective effects

We found that fluctuations in the number of emitters lead to a super-thermal photon statistics of small LEDs in a linear regime, with a strong emitter-field coupling and a bad cavity favorable for collective effects. A simple analytical expression for the second-order correlation function g_2 is found. g_2 increase up to g_2=6 in the two-level LED model is predicted. The super-thermal photon statistics is related to the population fluctuation increase of the spontaneous emission to the cavity mode.

quant-ph↗

arXiv2024

Spontaneous emission, collective phenomena and the efficiency of plasmon-stimulated photo-excitation

We find that the spontaneous and collective emissions have a strong influence on the excitation of two-level absorbers (atoms, molecules) interacting in resonance with the plasmonic mode near the metal nanoparticle. The spontaneous and collective emissions limit the absorption enhancement by the plasmonic mode and make the enhancement possible only with a fast, picosecond population relaxation of the upper absorbing states. Conditions for the maximum of plasmon-enhanced absorption in the presence of spontaneous and collective emissions are found. The nonlinearity in the nanoparticle-absorber interaction and in collective emission causes the bistability in the plasmon-enhanced absorption at high external field intensities and the plasmonic mode excitation.

physics.optics↗

arXiv2023

Single photon optical bistability

We investigate the bistability in a small Fabry-Perot interferometer (FPI) with the optical wavelength size cavity, the nonlinear Kerr medium and only a few photons, on average, excited by the external quantum field. Analytical expressions for the stationary mean photon number, the bistability domain, the field and the photon number fluctuation spectra are obtained. Multiple stationary states of the FPI cavity field with different spectra are possible at realistic conditions, for example, in the FPI with the photonic crystal cavity and the semiconductor-doped glass nonlinear medium.

quant-ph↗

arXiv2022

Quantum fluctuations in the small Fabry-Perot interferometer

We consider the small, of the size of the order of the wavelength, interferometer with the main mode excited by a quantum field from a nano-LED or a laser. The input field is detuned from the interferometer mode with, on average, a few photons. We find the field and the photon number fluctuation spectra inside and outside the interferometer and identify the contributions of quantum and classical noise in the spectra. Structures of spectra are different for the field, the photon number fluctuations inside the interferometer; for the transmitted, and the reflected fields. We note asymmetries in spectra. Differences in the spectra are related to the colored (white) quantum noise inside (outside) the interferometer. We calculate the second-order time correlation functions; they oscillate and be negative under certain conditions. Results help the study, design, manufacture, and use small elements of quantum optical integrated circuits, such as delay lines and optical transistors.

quant-ph↗

arXiv2022

Oscillator laser model

A laser model is formulated in terms of quantum harmonic oscillators. Emitters in the low lasing states are usual harmonic oscillators, and emitters in the upper states are inverted harmonic oscillators. Diffusion coefficients, consistent with the model and necessary for solving quantum nonlinear laser equations analytically, are found. Photon number fluctuations of the lasing mode and fluctuations of the population of the lasing states are calculated. Collective Rabi splitting peaks are predicted in the intensity fluctuation spectra of the superradiant lasers. Population fluctuation mechanisms in superradiant lasers and lasers without superradiance are discussed and compared with each other.

quant-ph↗

arXiv2022

Perturbation approach in Heisenberg equations for lasers

Nonlinear Heisenberg-Langevin equations are solved analytically by operator Fourier-expansion for the laser in the LED regime. Fluctuations of populations of lasing levels are taken into account as perturbations. Spectra of operator products are calculated as convolutions, preserving Bose commutations for the lasing field operators. It is found that fluctuations of population significantly affect spontaneous and stimulated emissions into the lasing mode, increase the radiation rate, the number of lasing photons and broad the spectrum of a bad cavity thresholdless and the superradiant lasers. The method can be applied to various resonant systems in quantum optics.

physics.optics↗

arXiv2022

Effect of Tamm surface states on hot electron generation and Landau damping in nanostructures metal-semiconductor

The hot electron generation in plasmonic nanoparticles is the key to efficient plasmonic photocatalysis. In the paper, we study theoretically for the first time the effect of Tamm states (TSs) at the interface metal-semiconductor on hot electron generation and Landau damping (LD) in metal nanoparticles. TSs can lead to resonant hot electron generation and to the LD rate enhanced by several times. The resonant hot electron generation is reinforced by the transition absorption due to the jump of the permittivity at the metal-semiconductor interface.

physics.optics↗

arXiv2021

Landau damping in hybrid plasmonics

Landau Damping (LD) mechanism of the Localized Surface Plasmon (LSP) decay is studied for the hybrid nanoplasmonic (metal core/dielectric shell) structures. It is shown that LD in hybrid structures is strongly affected by permittivity and electron effective mass in the dielectric shell in accordance with previous observations by Kreibig, and the strength of LD can be enhanced by an order of magnitude for some combinations of permittivity and effective mass. The physical reason for this effect is identified as electron spillover into the dielectric where electric field is higher than in the metal and the presence of quasi-discrete energy levels in the dielectric. The theory indicates that the transition absorption at the interface metal-dielectric is a dominant contribution to LD in such hybrid structures. Thus, by judicious selection of dielectric material and its thickness one can engineer decay rates and hot carrier production for important applications, such as photodetection and photochemistry.

physics.optics↗

arXiv2020

Electrostatic control over optically-pumped hot electrons in optical gap antennas

We investigate the influence of a static electric field on the incoherent nonlinear response of an unloaded electrically-contacted nanoscale optical gap antenna. Upon excitation by a tightly focused near-infrared femtosecond laser beam, a transient elevated temperature of the electronic distribution results in a broadband emission of nonlinear photoluminescence (N-PL). We demonstrate a modulation of the yield at which driving photons are frequency up-converted by means of an external control of the electronic surface charge density. We show that the electron temperature and consequently the N-PL intensity can be enhanced or reduced depending on the command polarity and the strength of the control static field. A modulation depth larger than 100\% is observed for activation voltages of a few volts.

physics.optics↗

arXiv2019

Effect of quantized conductivity on the anomalous photon emission radiated from atomic-size point contacts

We observe anomalous visible to near-infrared electromagnetic radiation emitted from electrically driven atomic-size point contacts. We show that the number of photons released strongly depends on the quantized conductance steps of the contact. Counter-intuitively, the light intensity features an exponential decay dependence with the injected electrical power. We propose an analytical model for the light emission considering an out-of-equilibrium electron distribution. We treat photon emission as bremsstrahlung process resulting from hot electrons colliding with the metal boundary and a find qualitative accord with the experimental data.

cond-mat.mes-hall↗

arXiv2019

On collective Rabi splitting in nanolasers and nano-LEDs

We analytically calculate the optical emission spectrum of nanolasers and nano-LEDs based on a model of many incoherently pumped two-level emitters in a cavity. At low pump rates we find two peaks in the spectrum for large coupling strengths and numbers of emitters. We interpret the double-peaked spectrum as a signature of collective Rabi splitting, and discuss the difference between the splitting of the spectrum and the existence of two eigenmodes. We show that an LED will never exhibit a split spectrum, even though it can have distinct eigenmodes. For systems where the splitting is possible we show that the two peaks merge into a single one when the pump rate is increased. Finally, we compute the linewidth of the systems, and discuss the influence of inter-emitter correlations on the lineshape.

quant-ph↗

arXiv2018

Biased Nanoscale Contact as Active Element for Electrically Driven Plasmonic Nanoantenna

Electrically-driven optical antennas can serve as compact sources of electromagnetic radiation operating at optical frequencies. In the most widely explored configurations, the radiation is generated by electrons tunneling between metallic parts of the structure when a bias voltage is applied across the tunneling gap. Rather than relying on an inherently inefficient inelastic light emission in the gap, we suggest to use a ballistic nanoconstriction as the feed element of an optical antenna supporting plasmonic modes. We discuss the underlying mechanisms responsible for the optical emission, and show that with such a nanoscale contact, one can reach quantum efficiency orders of magnitude larger than with standard light-emitting tunneling structures.

cond-mat.mes-hall↗

arXiv2016

Excitation of plasmonic nanoantennas with nonresonant and resonant electron tunnelling

A rigorous theory of photon emission accompanied inelastic tunnelling inside the gap of plasmonic nanoantennas has been developed. The disappointingly low efficiency of the electrical excitation of surface plasmon polaritons in these structures can be increased by orders of magnitude when a resonant tunnelling structure is incorporated inside the gap. Resonant tunnelling assisted surface plasmon emitter may become a key element in future electrically-driven nanoplasmonic circuits.

physics.optics↗

arXiv2015

Spontaneous hot-electron light emission from electron-fed optical antennas

Nanoscale electronics and photonics are among the most promising research areas providing functional nano-components for data transfer and signal processing. By adopting metal-based optical antennas as a disruptive technological vehicle, we demonstrate that these two device-generating technologies can be interfaced to create an electronically-driven self-emitting unit. This nanoscale plasmonic transmitter operates by injecting electrons in a contacted tunneling antenna feedgap. Under certain operating conditions, we show that the antenna enters a highly nonlinear regime in which the energy of the emitted photons exceeds the quantum limit imposed by the applied bias. We propose a model based upon the spontaneous emission of hot electrons that correctly reproduces the experimental findings. The electron-fed optical antennas described here are critical devices for interfacing electrons and photons, enabling thus the development of optical transceivers for on-chip wireless broadcasting of information at the nanoscale.

physics.optics↗

arXiv2014

Transition absorption as a mechanism of surface photoelectron emission from metals

Transition absorption of electromagnetic field energy by an electron passing through a boundary between two media with different dielectric permittivities is considered both classically and quantum mechanically. It is shown that transition absorption can make a substantial contribution to the process of electron photoemission from metals due to the surface photoelectric effect.

cond-mat.mes-hall↗

arXiv2014

Giant Photogalvanic Effect in Metamaterials Containing Non-Centrosymmetric Plasmonic Nanoparticles

Photoelectric properties of metamaterials containing non-centrosymmetric, similarly oriented metallic nanoparticles embedded in a homogeneous semiconductor matrix are theoretically studied. Due to the asymmetric shape of the nanoparticle boundary, photoelectron emission acquires a preferred direction, resulting in a photocurrent flow in that direction when nanoparticles are uniformly illuminated by a homogeneous plane wave. This effect is a direct analogy of the photogalvanic (or bulk photovoltaic) effect known to exist in media with non-centrosymmetric crystal structure, such as doped lithium niobate or bismuth ferrite, but is several orders of magnitude stronger. Termed the giant plasmonic photogalvanic effect, the reported phenomenon is valuable for characterizing photoemission and photoconductive properties of plasmonic nanostructures, and can find many uses for photodetection and photovoltaic applications.

physics.optics↗