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Application

• To convert CO₂-laser radiationinto second, third and fourth harmonics;
• To convert CO-laser radiation into second harmonic;
• To generate sum and difference frequencies of radiation of CO- and CO₂-lasers, as well as solid-state lasers generating at 1-3µm;
• To create parametric light oscillators tunable in a wide spectral range (from 3 to 10 µm) at pumping with 2-µm laser radiation;
• To create submillimeter radiation sources based on generation of difference frequency of two radiation lines of CO₂-or CO-lasers.

 

Specifications

Composition, formula - ZnGeP₂

Crystal structure - tetragonal, chalcopyrite

Point symmetry group  - ‾42m

Lattice parameters - a - b - 5.467 Å : c - 10.710 Å

Melting point  - 1027 ± 3 °C

Density - 4.158 g/cm³

Microhardness - 980 ± 80 kg/mm²

Mohs hardness - 5.5

Thermal conductivity - 0.18 W/(cm •K)

Heat capacity - 0.392 J/(g •K)

Effective transmission band - 2-12 µm

Optical symmetry - positive uniaxial birefringent - ne>no

 

Function

Frequency converters based on nonlinear optical materials solve the problem on creation of coherent optical sources generating  in spectral ranges unattainable for other methods of light generation. The most urgent is creation of coherent sources that allow new approach to solving many  problem in high- and superhigh- resolution spectroscopy.

Single crystal of zink germanium diphosphide (ZnGeP₂) is the most virtual nonlinear material in the middle IR range (0.7 - 12 µm). The figure of merit of ZnGeP₂ crystal characterizing  potential efficiency of parametric frequency conversion has a value M=(d₁₄)²/n³ = 210•10^-24 m²v^-2

 

Merits

High damage threshold; thermal conductivity providing tolerance for thermocycling; large values of temperature, angular and spectral phase matching  widths, that facilitate optical channel alignement and tuning of frequency converters based on  single ZnGeP₂ crystals to phase matching; mechanical strength providing stable operation under vibrations; crystal resistance to high humidity and even to corrosive media.

All these unique characteristics make the material promising for producing optical elements and applying them into different optical devices and systems.

 

Based on studies of grounds of optical loss in ZnGeP₂ crystals, Design and Technology Laboratory of IMCES SB RAS developed a technological process providing growth of high quality ZnGeP₂ single crystals with optical loss diminished  to 0.02-0.04 cm^-1 at wavelength of ~ 2µm.

The most essential advance is development of a technological process fully complying to lot production requirements and providing growth of ZnGeP₂ single crystals of high optical quality with the yield of ~50%.