Alexander I. Smirnov

Two-photon luminescence imaging by scanning near-field optical microscopy for characterization of gold nanoparticles

Spatial distribution of a two-photon luminescence signal when gold nanoparticles on the surface are scanned by the tip of an atomic force microscope irradiated by femtosecond laser radiation was studied in an experiment. Comparison of the experimental data with the results of numerical simulation of two-photon luminescence based on a finite-difference time-domain calculation of electric field distribution in the nanoparticle–tip system can give information on the shape and orientation of the nanoparticles.

Second harmonic generation and two-photon luminescence from colloidal gold nanoparticles

Second harmonic generation and two-photon luminescence from colloidal gold nanoparticles in the 980–1300 nm wavelength range of exciting femtosecond radiation were investigated experimentally. The measured polarization and spectral characteristics of the second harmonic and two-photon luminescence demonstrate that the observed nonlinear optical signal is determined by the dimers constituting several percent of the total nanoparticle number.

Guiding properties of metamaterials

This paper is devoted to detailed research of an opportunity to use modern metamaterials for an efficient guiding of electromagnetic waves of various ranges (mainly: giga- and terahertz). The following basic questions are considered: the true surface waves [1] guided boundary of the metamaterial; the surface waves guided by layers of a metamaterial; the localized waves in lattices of resonance microelements. The special regard is devoted to mechanism of formation backward waves in discrete systems.

Nonlinear optical diagnostics of gold nanoparticles by atomic-force microscopy and femtosecond laser pulses

This work is devoted to studying the possibilities of using a femtosecond laser facility and a scanning atomic-force microscope (AFM) for nonlinear optical diagnostics. The developed technique ensures an optical resolution of 30 nm for gold nanoparticles. It is shown that the presence of the AFM tip significantly affects the nonlinear optical response of separate gold nanoparticles.

Second-harmonic generation by resonant high-index dielectric nanoparticles

By combining analytical and numerical approaches, we study resonantly enhanced second-harmonic (SH) generation by individual high-index dielectric nanoparticles made of centrosymmetric materials. Considering both bulk and surface nonlinearities, we describe second-harmonic nonlinear scattering from a silicon nanoparticle optically excited in the vicinity of the magnetic and electric dipole resonance. We discuss the contributions of different nonlinear sources and the effect of the lowest-order optical Mie modes on the characteristics of the generated far-field. Our findings uncover important implications for design of nonlinear nanoantennas fully integrable with silicon-based photonic circuits.

Nonlinear scattering of laser radiation by high-refractive-index nanoparticles

We develop the asymptotic theory of third-harmonic generation from silicon nanoparticles driven by optically-induced Mie resonances and analyze the multipolar nature of the generated electromagnetic fields. We propose the approaches for directing the resonantly enhanced nonlinear scattering by spherical and disk-shaped particles, excited in the vicinity of the magnetic dipolar resonance. Our analytical results are supported by direct full-wave numerical simulations.

Dimer impact on second harmonic generation and two-photon luminescence from colloidal gold nanoparticles

The second harmonic generation and two-photon luminescence from a colloidal solution of spherical gold nanoparticles at wavelength tuning of exciting radiation is studied in experiments. The measured polarization and spectral characteristics of the second harmonic and two-photon luminescence demonstrate that the observed nonlinear optical response is determined by the dimers that constitute several percent of the total nanoparticle number.

Numerical calculation of nonlinear-optical interaction of gold nanoparticle and atomic force microscopy probe

We numerically simulated two-photon luminescence at the near-filed interaction of a gold nanoparticle and a conductive atomic-force microscope tip (AFM) using FDTD calculation of electric field distribution. Comparison of the results of numerical simulation with the experimental data [1] gives information on the shape and orientation of the nanoparticles with a resolution surpassing that of conventional methods of atomic force microscopy.

Self-action effects for the laser radiation scattered by metal nanoparticles

The self-action effects of the laser radiation incident on metal nanoparticles of spherical shape are analyzed within the framework of a free-electron model and a phenomenological description of the nonlinear electrodynamic properties of the metal surface. Analytical expressions are obtained for the nonlinear addition to the field-induced dipole moment of a nanoparticle at the fundamental frequency. The theory we developed explains the experimentally observed features typical of the nonlinear susceptibility of the dielectric materials containing nanosized metal inclusions.

Channelling of a microwave discharge by a plasma filament created in atmospheric air by an intense femtosecond laser pulse

We study the initiation of a pulsed microwave discharge in atmospheric air by a plasma channel induced by intense femtosecond laser pulses. It is shown that the electric field threshold for the initiated discharge is lowered compared with the self-discharge by about a factor of two, from 25 to 12 kV·cm−1. Channelling of the atmospheric-pressure microwave discharge in the direction of the plasma filament has been detected. The time of existence of the initiated discharge plasma was determined by the duration of the microwave pulse and amounted to 1–2 μs for the maximum electron density estimated as about 4 × 1015 cm−3. The developed theory of propagation of the microwave radiation along the plasma channel created by a femtosecond laser pulse predicts that the relatively low conductivity of the plasma and its rapid decay limit the characteristic scale of decay of the microwave fields confined by the plasma channel to a few centimeters.