V. N. Streltsov

Parametric Acoustic Switches, Modulators, and Detectors

The sound wave passage through a parametrically active layer of a material with a quasistatic variation in the speed of sound was calculated. General expressions for the space-time evolution of an incident monochromatic beam were derived and the layer transmittance was determined.

High-resolution four-wave mixing spectroscopy of suspensions: the nonlinear mechanism of a Rayleigh-wing formation

Results of theoretical and experimental investigations of the nonlinear mechanism of Rayleigh-wing formation during the four-wave mixing process in suspensions are presented. The developed theory shows that simultaneous action of two laser radiations with different wavelengths on a spherical particle in a viscous liquid causes a nonlinear resonant response, whose width depends in a complex manner on the particle size, its mechanical properties and the bulk and shear viscosity of the surrounding liquid. The diffusion of particles in a liquid, which depends on several parameters including concentration, leads to concentration dependence of the resonance linewidth observed in the experiment. The four-wave mixing spectroscopy allows us to directly observe nonlinear Rayleigh scattering resonances in the suspensions of spherical nanoparticles whose bandwidth lies in the range from 20 MHz (7 × 10−4 cm−1) to 150 MHz (5 × 10−3 cm−1). These resonances are observed at a high enough level of the detected signal and the signal/noise ratio achieved in the individual measurements is of two orders of magnitude.

Two-frequency parametric generation of sound in acoustic resonator

Steady-state parametric generation of sound in an acoustic resonator with time modulation of the speed of sound in a resonator material was theoretically studied taking into account quadratic nonlinearity of a medium.

Parametric generation of short acoustic pulses

A method of parametric generation of short sound pulses with controllable duration upon excitation of steady-state vibrations of the acoustic field in the resonator under conditions of modulation of the amplitude of high-frequency variations in the speed of sound in a resonator material was proposed and theoretically studied.

Four-photon polarization spectroscopy of induced plasma oscillations in a skin layer of semiconductors

Probe-beam scattering spectra have been obtained for four-wave mixing of laser waves in the skin layer of intrinsic semiconductors. The spectra were recorded using the frequency dispersion of orthogonally polarized radiation, which arises as a result of nonlinear optical interaction with conduction-band electrons. The mixing of two counterpropagating light waves in a semiconductor, implemented under nonlinear excitation of longitudinal density oscillations in the plasma electron subsystem of the semiconductor, is theoretically considered. This mixing is shown to lead to the rotation of the probe-beam polarization vector. The results obtained are of interest, e.g., for studying optical metamaterials based on thin-film structures.

Low-frequency four-photon spectroscopy of surface waves in semiconductors: A new mechanism of optical nonlinearity

A new mechanism of optical nonlinearity of intrinsic semiconductors is proposed, which is based on bandgap modulation due to the four-wave mixing of interacting waves on the semiconductor surface. This phenomenon is theoretically considered within a one-dimensional model. The corresponding resonances are experimentally found in Ge and Si samples.

High-Resolution Spectroscopy at Steady-State Lasing with Multiphoton Backscattering

A steady-state self-consistent lasing regime in a laser cavity is investigated with allowance for the back action of the output radiation at four-wave low-frequency scattering in the external sample. The scattering is by the photoelastic potential in the field of the additional opposing laser. General expressions for steady-state amplitudes of field oscillation in the cavity are obtained and employed for investigation of lasing features. Experiments were carried out with narrow-band (line width 1 MHz) continuously tunable diode lasers. The four-wave scattering occurred in solid and liquid dielectrics. It is shown that the fourwave scattering of the pumping laser radiation into the cavity of the signal laser substantially changes its lasing spectrum and can be used to measure dispersion of acousto-optic parameters.

Passage of sound wave through a resonant parametric layer: Theory

General expressions were derived for the transmittance and reflectance at normal incidence of a monochromatic sound wave on a plane-parallel layer with a modulated speed of sound at a resonant layer thickness.

Low-frequency laser spectroscopy of cylindrical nanoparticle suspensions

A theory of generation of anti-Stokes radiation on the eigenvibrations in a suspension of cylindrical nanoparticles in the field of two copropagating electromagnetic pump waves has been developed. Surface ponderomotive forces are shown to induce acoustic vibrations and dipolemoments of nanoparticles at the anti-Stokes frequency. Under these conditions, the scattering efficiency depends on the dielectric characteristics of the solution and the acoustic parameters of the liquid and solid fractions of the suspension. Experiments on stimulated low-frequency Raman scattering of laser radiation in aqueous suspensions of tobacco mosaic virus in a buffer solution have been performed. A coherent signal of the Stokes component with a frequency shift of ≈60GHz is detected; this value is in good agreement with the estimated frequency shift for stimulated excitation of eigenvibrations of cylindrical nanoparticles in a liquid: ≈50 GHz.

Laser-controlled semiconductor acoustic switches and modulators

The transmission of a sound wave through a plane-parallel semiconductor layer excited by a laser beam with adiabatically slow temporal change in intensity is investigated. Phonon-plasmon interaction on the deformation potential is implemented in the layer. It is shown that this system can be used as an efficient acoustic switch or a modulator.