A.N. Morozov

CO laser frequency conversion in nonlinear crystals ZnGeP2 and GaSe

Experimental and modeling results on CO laser frequency conversion are presented. A Q-switched multiline CO laser with pulse repetition rate 20-150 Hz of sub-microsecond pulses and electron beam sustained discharge frequency-tunable mode-locked CO laser were used in the experiments on second harmonic generation (SHG) in high-quality ZnGeP2 and GaSe crystals. Internal SHG efficiency exceeded 12.4 % in 12 mm ZnGeP2 crystal. The SHG in 4 mm GaSe crystal was observed with internal efficiency of 0.3%. A possibility of difference frequency generation of fundamental and firstovertone CO laser lines to cover spectral range of ~4.0-5.0 μm is discussed. It is estimated that the difference frequency generation of neighboring lines of both fundamental and first-overtone bands allows one to obtain oscillation in THz spectral range within ~200-3000 μm.

GaSe 1−x S x crystals for teraherz frequency range

GaSe1−xSx single crystals has been grown by Bridgman-Stockbarger technique. Structural quality has been evaluated with TEM observation. Terahertz time-domain spectroscopy has been applied for measurements of the frequency-dependent optical constant of doped GaSe crystals as a function of s-content.

Properties of gallium selenide doped with sulfur from melt and from gas phase

This paper presents the results of investigation on influence of doping with sulfur and annealing in sulfur atmosphere on properties of promising nonlinear optical gallium selenide crystals, grown by the Bridgeman method from melts with content of sulfur 0.01-3 mass % and annealed in sulfur atmosphere.

S-Doped GaSe for sub-microwave generation

The near IR and sub-microwave range optical properties of AgGaS2-doped GaSe (GaSe:AgGaS2) grown in accordance with chemical formula [2(GaSe)]1−x:(AgGaS2)x, x=0.1, in charge composition, were studied in comparison with that in 2 wt% and 10.2 wt% S-doped GaSe (GaSe:S) to reveal the potentials for phase matching and frequency conversion from near IR into sub-microwave range by down-conversion of fs Ti:Sapphire laser emission. The composition of grown GaSe:AgGaS2 crystal is identified as GaSe:S (2.19 mass%). The crystal possesses 25% higher hardness comparing to that of GaSe:S(2 mass%) grown by traditional technique, can be cut and polished, and is useful in applied systems. It was found that GaSe:S possesses the best set of physical properties for sub-microwave and microwave generation among doped GaSe crystals.

Physical properties of electrooptical GaSe:Al

Physical properties of Al-doped GaSe or GaSe:Al(0.01, 0.02, 0.05, 0.1, 0.5, 1, 2 wt%) crystals in charge composition were studied in comparison with pure GaSe to reveal the potentials for sub- and microwave elec-trooptical application. Aluminium was not detected in GaSe:Al by X-ray chemical analysis. It was found that resistivity of GaSe:Al drastically increases with Al doping up to 10⁵−10⁷ in comparison with (1–3)·10² in pure GaSe and 10³ Om-cm in GaSe:S(2 wt%). No significant changes in optical properties to that in GaSe (α≤0.1–0.2cm⁻¹) were found at 0.01–0.02 wt% Al-doping but 2-fold to 3-fold increase in hardness at 0.5 wt% Al-doping. GaSe physical properties modified by Al-doping make it very attractive for mid-IR and sub-microwave electrooptic applications.

Study of GaSe 1−x S x properties for terahertz applications

For prospective nonlinear crystals GaSe<inf>1−x</inf>S<inf>x</inf> experimental study of second harmonic generation processes of Er³⁺:YSGG-, CO<inf>2</inf>- and CO-lasers has been performed, control experiment on difference frequency generation of two lines of CO<inf>2</inf>-laser has been realized, the transmission spectra and dispersion of complex refractive indices in terahertz range have been measured.

Structure, Defects, Mechanical and Optical Properties of Hexagonal Semiconductor GaSe 1-X S x Single Crystals at 0<X<0.4

Structure, defects, mechanical and optical properties of GaSe_1-xS_x, 0<x<0.4, matters and single crystals are presented.