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%.