Modified GaSe crystal as a parametric frequency converter

Phase matching for the second harmonic generation in GaSe crystals

“…The PM angles measured for the second harmonic generation of СО 2 and Er 3+ :YSGG lasers and AgGaS 2 OPO in the majority of the examined crystals in the wavelength range 2.5−10.8 μm were in good agreement with the PM diagrams calculated with dispersion data of [11,13] as well as with the majority of the well-known experimental data [10,12,13,21,23,24]. The bright exceptions are only experimental data presented in [3].…”

GaSe1−x S x solid solutions

“…The growth of the GaSe 1-x S x solid solutions with sulfur contents up to 0.01-0.03 mass% led to the reduction of the coefficient of linear optical losses by two orders of magnitude in comparison with the available technology of pure GaSe crystal growth and to an increase in the generation efficiency of the second harmonic of a СО 2 laser by a factor of 2.25 in comparison with the wealkly doped (0.1 mass%) GaSe:In crystals [8]. Such situation confirms that a detailed study of the physical properties of GaSe 1-x S x solid solutions with mixing ratio x and dopant content >1-3 mass% is urgent.…”

“…The GaSe:Er (0.5 mass%) crystals kept their hexagonal structure unchanged and demonstrated a 24% increase in the second-order nonlinear susceptibility coefficient [11]. In turn, doping with sulfur led to a noticeable improvement of all physical properties of the GaSe crystals: improvement of cleavage with the corresponding reduction of the coefficient of linear optical losses in comparison with pure GaSe crystal grown by the available technology, increase in the nonlinear susceptibility coefficient, and shift of the absorption spectrum toward shorter wavelengths [7][8][9][10]. We note that the shift of the absorption spectrum toward shorter wavelengths must result in the corresponding reduction of the nonlinear optical losses.…”

“…Exactly this circumstance limits the energy parameters of laser radiation in the range 0.7-1.3 µm converted into the middle IR and terahertz ranges. In particular, the power of dye laser pulses converted into the middle IR range is limited by a subkilowatt level [1, [3][4][5][6][7][8][9][10][11].…”

Dispersion properties of GaSe1-x S x in the terahertz range

“…It has been established that besides the mechanical properties, other key physical properties of GaSe crystals can be controllably modified by selection of the sulfur content. Introducing large concentrations of sulfur, indium, and tellurium (leading to a change in the lattice parameters) have the best possibilities in this regard; in other words, growing nonlinear crystals of solid solutions according to the chemical formulas GaSe:GaS → GaSe 1-x S x [4], [12][13][14][15][16][17][18][19], GaSe:InSe → Ga 1-x In x Se [5,7], and GaSe:GaTe → GaSe 1-x Te x [8,9]. Introducing small sulfur ions eliminates cleavage defects in the GaSe crystals and reduces linear optical losses in the region of maximum transparency (optimal doping level, 2-3 wt.%), and also increases the thermal conductivity severalfold orthogonal to the growth layers, as a result of substitution of selenium ions, filling vacancies, and intercalation in the interlayer space.…”