V. M. Parfenyev

Nonlinear Generation of Vorticity by Surface Waves.

We demonstrate that waves excited on a fluid surface produce local surface rotation owing to hydrodynamic nonlinearity. We examine theoretically the effect and obtain an explicit formula for the vertical vorticity in terms of the surface elevation. Our theoretical predictions are confirmed by measurements of surface motion in a cell with water where surface waves are excited by vertical and harmonic shaking the cell. The experimental data are in good agreement with the theoretical predictions. We discuss physical consequences of the effect.

Quantum theory of a spaser-based nanolaser

We present a quantum theory of a spaser-based nanolaser, under the bad-cavity approximation. We find first- and second-order correlation functions g(1)(τ) and g(2)(τ) below and above the generation threshold, and obtain the average number of plasmons in the cavity. The latter is shown to be of the order of unity near the generation threshold, where the spectral line narrows considerably. In this case the coherence is preserved in a state of active atoms in contradiction to the good-cavity lasers, where the coherence is preserved in a state of photons. The damped oscillations in g(2)(τ) above the generation threshold indicate the unusual character of amplitude fluctuations of polarization and population, which become interconnected in this case. Obtained results allow to understand the fundamental principles of operation of nanolasers.

Allowable number of plasmons in nanoparticle

We address thermal and strength phenomena occurring in metal nanoparticles due to excitation of surface plasmons. The temperature of the nanoparticle is found as a function of the plasmon population, allowing for the Kapitza heat boundary resistance and temperature dependencies of the host dielectric heat conductivity and the metal electrical conductivity. The latter is shown to result in the positive thermal feedback which leads to appearance of the maximum possible number of plasmon quanta in the steady-state regime. In the pulsed regime the number of plasmon quanta is shown to be restricted from above also by the ponderomotive forces, which tend to deform the nanoparticle. Obtained results provide instruments for the heat and strength management in the plasmonic engineering.

Effects of thin film and Stokes drift on the generation of vorticity by surface waves

Recently a theoretical scheme explaining the vorticity generation by surface waves in liquids was developed [Phys. Rev. Lett. 116, 054501 (2016)PRLTAO0031-900710.1103/PhysRevLett.116.054501]. Here we study how a thin (monomolecular) film presented on the surface of liquid affects the generated vorticity. We demonstrate that the vorticity becomes parametrically larger than for the case of liquid with a free surface, and the parameter is the quality factor of surface waves up to numerical factor. We also discuss the PIV experimental scheme intended to observe the generated vorticity and find that Stokes drift influences the measured velocity field. Explicit expression for the vertical vorticity was obtained.

Nonlinear generation of vorticity in thin smectic films

We analyze a solenoidal motion in a vertically vibrated freely suspended thin smectic film. We demonstrate analytically that transverse oscillations of the film generate two-dimensional vortices in the plane of the film owing to hydrodynamic nonlinearity. An explicit expression for the vorticity of the in-plane film motion in terms of the film displacement is obtained. The air around the film is proven to play a crucial role, since it changes the dispersion relation of transverse oscillations and transmits viscous stresses to the film, modifying its bending motion. We propose possible experimental observations enabling to check our predictions.

Negative-angle refraction and reflection of visible light with a planar array of silver dimers

We study the plane wave scattering on a planar periodic array of silver dimers. It is found that an appropriately designed array provides the sharp turn of TE-polarized incident beam in orthogonal (opposite) directions through the effects of negative-angle refraction (reflection).

Thermal phenomena in quantum plasmonics

Plasmon nanolasers, also known as SPASERs, were suggested by Bergman and Stockman in 2003. Quantum plasmonics attract much attention in recent years due to the numerous potential applications in the plasmonics. We consider thermal effects in the metal nanoresonator immersed in the active, laser medium. The size of the resonator is much less than the wavelength. The plasmon field inside the nanoresonator operates as a quantum object. Due to the nanosize of the resonator, the internal plasmon electric field is about the atomic field even for few plasmon quants. The coupling between the plasmon field and plasmon resonator is anomalous strong. We develop the quantum dynamics of the plasmon field and show that the SPASER may be the subject of thermal instability. The loss in SPASER increases with increasing the temperature when the average number of the plasmons is maintained at the stationary level. Therefore, the heat generation increases with increasing the temperature. This positive feedback results in the thermal instability. When the energy, accumulated in the plasmon nanoresonator, exceeds the instability threshold the temperature increases exponentially. We find the increment of the temperature growth and lifetime as function of the loss in metal and the structure of the plasmon resonator. We consider how the thermal instability influences the luminescence and find how the lasing threshold is changed. The coherence of the light emitted by the plasmon laser is also considered. The thermal stability of the nanolaser is crucial for any practical application.

Thermal instability in plasmonics

The quantum-mechanical and thermal phenomena in the plasmonic nanoparticle and resonator are investigated. We develop quantum plasmonics by quantizing the collective electron motion in the surface plasmon. The operator of the electric field inside the metal nanoparticle is found. Thus obtained quantum electric field is anomalous large even for few plasmon quanta. The strong electric field, which value is comparable with the atomic field, results in huge electric current and overheating the metal nanoparticle when it operates as a resonator for the plasmon laser (SPASER). It is shown the overheating thermal instability can explode the particle.

Spaser in above-threshold regime: The lasing frequency shift

Operation of spaser-based nanolaser is considered theoretically. We establish that the dependence of the lasing frequency undergoes red-shift with the increase of the pumping intensity. We propose, that the mechanism leading to the red-shift is based on space deformation of the lasing mode, which is induced by inhomogeneous depletion of the gain media. We develop general analytical scheme which allows to account the mode deformation.