A. P. Shkurinov

Enhancement of second-harmonic generation with femtosecond laser pulses near the photonic band edge for different polarizations of incident light

We present experimental evidence of enhancement of second-harmonic generation as a result of an increase of the fundamental-field energy density within a multilayer structure near the photonic band edge.

The use of combination of nonlinear optical materials to control terahertz pulse generation and detection

We suggest composite nonlinear optical media based on the pair of ZnTe and GaP crystals for terahertz pulse detection or generation. The influence of laser wavelength, pulse duration, and media thickness on the terahertz pulse conversion are studied. The optimization of the composite structure performed numerically allowed for essential improvement of the phase-matching condition observed in the experiment.

Time-resolved spontaneous and coherent raman scattering of Ni-octaethylporphyrin in excited electronic states

Abstract The results are presented of a detailed analysis of the vibrational structure of the excited triplet electronic state T d of Ni-octaethylporphyrin (Ni-OEP) in solution by means of spontaneous and coherent Raman scattering spectroscopy. The application of these two methods generated complementary information about the characteristics of the T d state.

Analysis of blood plasma at terahertz frequencies

Terahertz time-domain spectroscopy in the 0.05-2.5 THz frequency range was employed to analyze blood plasma samples obtained from laboratory animals with experimental diabetes and from healthy controls. It was found that transmission and reflection coefficients of samples from rats with diabetes differed significantly from control values in both amplitude and phase. The cause of the detected differences is discussed with respect to variation in the terahertz response of water.

Experimental observation of the interference of three-and five-wave mixing processes in optical second harmonic generation in a solution of bacteriorhodopsin

The generation of a femptosecond second harmonic in a bacterior-hodopsin solution is investigated. It is shown that the behavior of the harmonic can be explained by the coherent interference of several contributions from three-and five-wave mixing processes (χ(2) and χ(4)). The magnitude and phase of the fourth-order electronic susceptibility χ(4) of the medium with respect to χ(2) are determined.

Theory of a laser-plasma method for detecting terahertz radiation

A theory is developed for calculating the spectrum and the shape of a terahertz wave packet from the temporal profile of the energy of the second harmonic of the laser field generated during nonlinear interaction of laser and terahertz pulses in an optical-breakdown plasma. The spectral and temporal characteristics of the second-harmonic envelope and a terahertz pulse are shown to coincide only for short laser pulses. For long laser pulses, the second-harmonic spectral line shifts to the red and its temporal profile is determined by the time integral of the electric field of terahertz radiation.

Studying human and animal skin optical properties by terahertz time-domain spectroscopy

Human and rat skin reflection spectra and the effect of glucose and glycerol on these spectra are studied in vivo by terahertz time-domain spectroscopy in the frequency range of 0.1–2.0 THz. Variations in skin optical properties proved to correlate with changes in the blood glucose level.

Polarization characteristics of the “forbidden” second optical harmonic of femtosecond laser pulses in a bacteriorhodopsin solution

The generation of the second harmonic of femtosecond laser pulses in a bacteriorhodopsin solution has been experimentally studied for various wavelengths and polarization states of radiation at the fundamental frequency. The polarization properties of the effect are analyzed under various experimental conditions. The nature and properties of the signal are treated as the manifestation of a superposition of nonlinear optical effects of various orders (the second and the fourth). The second-order effects can have both an electric-dipole and a magnetic-dipole or electric-quadrupole character. In analyzing fourth-order processes, besides the direct electric-dipole contribution, the possibility of the participation of cascade processes at second-and third-order nonlinearities is also allowed.

Band gaps in the spectra of terahertz surface plasmons on metallic diffraction gratings

The effect of the appearance of band gaps in the energy spectra of terahertz surface plasmons has been experimentally observed and investigated. The band gaps are formed due to the interference interaction of the surface plasmons excited by pulsed terahertz radiation on metallic diffraction gratings. It has been shown that the experimental dispersion curves of terahertz plasmons are in good agreement with the dispersion curves obtained in the numerical simulation.

Light-induced director reorientation in nematic liquid crystal under femtosecond pulses

The interaction of a nematic liquid crystal (NLC) with the succession of the femtosecond light pulses has been investigated. Direct experimental comparison between the nonlinear NLC response to femtosecond and cw radiation was performed.