A. I. Gribenyukov

ZnGeP2 synthesis and growth from melt

Abstract The two-temperature technique has been examined for ZnGeP2 synthesis. The effect of the cold zone temperature on the Zn diffusion and the ZnP2 formation outside the ternary compound reaction zone has been studied. A qualitative analysis of the Zn diffusion equation taking into account the P mass transport has allowed us to identify conditions where no Zn diffusion is observed. The effect of the ampoule surroundings on the ZnGeP2 crystal growth has been investigated for the vertical Bridgman and vertical gradient freezing methods. The steady-state thermal conductivity equation has been solved for different ampoule surroundings. The proposed numerical model has established the reasons for the polycrystalline structure and physical properties heterogeneity of ZnGeP2 crystals, viz. the isotherm concavity and variable growth rate with respect to the ampoule translation speed.

Beam-path gas analyzer based on a tunable CO2 laser with frequency doubling

In an attempt to bring the high power and versatility of carbon dioxide lasers to bear on atmospheric measurements for pollutants such as carbon monoxide, nitrogen oxides, and sulfur dioxide, the authors propose parametric frequency converters for carbon dioxide laser radiation in the spectral range required. Field measurements are discussed of the densities of a number of atmospheric gas components, including CO, and of the transparency of the atmosphere to beam paths using a beam-path gas analyzer containing a frequency doubler for a carbon dioxide laser based on the zinc phosphide-germanium phosphide monocrystal. The KAMAK MERA-60 computer system 23 does programmed tuning of the carbon dioxide laser radiation wavelength by rotation of a diffraction grating.

Submillimeter-wave generation with ZnGeP2 crystals

This paper describes detailed analysis of optical and dielectric properties of ZnGeP2 crystals in middle IR and FIR spectral ranges, and also first experimental results on 1 W level 102 - 110 micrometers emission generation by means of difference frequency generation of CO2 laser line pairs. It is shown that MW level is achievable now, and AgIn0.35Ga0.65Se2 crystal can be used for efficient generation of FIR emission.

Far-infrared generation by CO2 lasers frequencies subtraction in a ZnGeP2 crystal

A pulsed radiation power of approximately 1 W was reached for the first time, with the aid of a ZnGeP2 crystal, at the difference frequency of CO2 lasers radiation in the submillimeter spectral range.

Mechanisms of loss formation in nonlinear optical crystals ZnGeP2 in the terahertz frequency range

Physical mechanisms of formation of radiation losses in the terahertz range in ZnGeP2 crystals have been experimentally studied in the wave number range of 5–350 cm−1 at temperatures of 10–300 K. The dominant contribution of two-phonon difference processes to the loss formation in the given frequency range has been shown.

Far infrared generation by CO2 lasers frequencies subtraction in a ZnGeP2 crystal

Abstracta pulsed radiation power of the order of 1W in the submillimeter range (102–110 µm) was reached for the first time, with the aid of a ZnGeP2 crystal, at the difference frequency of CO2 laser radiations.

Effect of electron irradiation of ZnGeP2 single crystals on terahertz losses in a wide temperature range

The reflection and transmission spectra of ZnGeP2 single crystals irradiated with 4-MeV electrons have been measured in the frequency range of 5-5000 cm−1 at temperatures in the range of 10-300 K. Based on the measured spectra, the spectra of complex permittivity ɛ*(ν) and absorption coefficient α(ν) have been simulated using the dispersion analysis method. It has been found that the electron irradiation decreasing the losses in the pumping range by a factor of 2–3 does not lead to additional losses in the region of generating terahertz radiation.

Modelling half-cycle pulse generation in ZnGeP2 crystal

For the first time for a ZnGeP2 crystal, the three-wave interaction of picosecond pulses was considered as the difference frequency generation. The group velocities and absorption of radiation were taken into account in performing a spectral analysis. The calculations of a radiation pulse were made for the following parameters of a CO2 laser: 100-1.25 ps and 15-1100 GW cm-2. At the 804.5 µm wavelength of difference frequency, the spectral characteristics have been obtained and the pulse power has been found as a function of crystal length. The half-cycle pulse generation is possible at a particular crystal length.

Simulation of parametric oscillation in the submillimeter range at pumping of the ZnGeP2 crystal by a train of 100-ps high-power pulses

Analysis is given for a possibility of singly resonant parametric oscillation in the submillimeter range at synchronous pumping of the ZnGeP2 crystal by a train of 100-ps second-harmonic pulses from the CO2 laser with the radiation energy 1.0 J. The calculation shows that using the ZnGeP2 crystal and the second harmonic of the CO2 laser with the energy density 1.8 J cm−2, one can get the peak submillimeter radiation power from 3.6 to 12 MW in the range from 95 to 300 µm (1.0–3.3 THz). The expected peak power values are larger than the experimental ones obtained by other nonlinear optics methods.

Parametric oscillation of high-power 3-THz pulse by synchronously pumped ZnGeP2 crystal: Computer simulation

Possible parametric oscillation of 3-THz pulse at synchronous pumping of the ZnGeP2 crystal by a train of short second-harmonic pulses from the CO2 laser has been analyzed. Calculation shows that at changing laser pulse duration τ between 4 and 500 ps and correspondingly pumping energy density (0.5–3.5 J cm−2) THz pulse peak power varies from 3 to 70MW with maximum at τ =9 ps.