Abstract
LiGaSe2 (LGSe) and LiInSe2 (LISe) are wide band-gap nonlinear crystals transparent in the mid-IR spectral range. LiGa0.5In0.5Se2 (LGISe) is a new mixed crystal, a solid solution in the system LGSe–LISe, which exhibits the same orthorhombic structure (mm2) as the parent compounds in the same time being more technological with regard to the growth process. In comparison with LGSe and LISe its homogeneity range is broader in the phase diagram. About 10% of the Li ions in LGISe occupy octahedral positions (octapores) with coordination number of 3. The band-gap of LGISe is estimated to be 2.94 eV at room temperature and 3.04 eV at 80 K. The transparency at the 0-level extends from 0.47 to 13 µm. LGISe crystals exhibit luminescence in broad bands centered near 1.7 and 1.25 eV which is excited most effectively by band-to-band transition. From the measured principal refractive indices and the fitted Sellmeier equations second-harmonic generation from 1.75 to 11.8 μm (fundamental wavelength) is predicted. The nonlinear coefficients of LGISe have values between those of LGSe and LISe. 6LGISe crystals are considered promising also for detection of thermal neutrons.
Highlights
The orthorhombic lithium ternary chalcogenides with the chemical formula LiBC2 where B=In andGa, C=S and Se, occupy a special position among the non-oxide nonlinear optical crystals because they are characterized by the widest band-gaps [1,2,3,4,5,6,7]
Their main advantage consists in the possibility to pump them at rather short wavelengths, without two-photon absorption (TPA), generating tunable mid-IR radiation by frequency down-conversion nonlinear optical processes [8]
The present paper presents information on the growth procedure, crystal structure, and the linear and nonlinear optical properties of LGISe
Summary
The orthorhombic lithium ternary chalcogenides with the chemical formula LiBC2 where B=In and. In the chalcopyrite family of nonlinear crystals AgBC2 , all four types of solid solutions have been studied but in the limit of AgInC2 , the birefringence is too low for phase-matching. E.g., amplified Ti:sapphire laser systems, the most advanced sources of high energy femtosecond pulses, can be used for pumping parametric amplifiers based on LGSe but not LISe the latter exhibits the highest nonlinearity among the LiBC2 compounds. This limitation is a consequence of the different band-gaps: as a result of this the TPA coefficient measured at 820 nm is
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