Single crystals LiGaX 2 (X = S, Se, Te) of optical quality were grown, with transparency ranges at 5 cm -1 absorption level of 0.32-11.6 µm, 0.37-13.2 µm and 0.54-14.2 µm, respectively. The first two, LiGaS 2 and LiGaSe 2 , have a wurtzite-type structure whereas LiGaTe 2 is tetragonal (chalcopyrite lattice). The three refractive indices were measured in the whole transparency ranges of LiGaS 2 and LiGaSe 2 and n a and n c were found to be very close (quasi-uniaxial optical anisotropy) with a crosspoint at 6.5 µm (LiGaS 2 ) and 8 µm (LiGaSe 2 ). Sellmeier equations were fitted and phase-matching conditions for second harmonic generation (SHG) were calculated: the 1.467-11.72 µm spectral range for the fundamental is covered by LiGaS 2 and LiGaSe 2 .

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The thermal conductivity and thermal-expansion and thermo-optic coefficients, the knowledge of which is essential for nonlinear optical applications, are measured along the three crystallographic axes of the newly discovered orthorhombic crystal LiInSe2. The latter has a nonlinear susceptibility only a quarter lower than that for the commercially available AgGaS2, but its advantages include ∼4 times higher thermal conductivity, ∼2 times lower thermo-optic coefficients, and the lack of sign inversion in thermal-expansion coefficients.

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Optical Applications in the Mid-IR. -Single crystals of the title compounds are synthesized from the elements using the Bridgman-Stockbarger technique and characterized by UV/VIS and Raman spectroscopy. LiGaS2 and LiGaSe2 crystallize in the orthorhombic space group Pna21 with Z = 4 and LiGaTe2 in the tetragonal space group I42d with Z = 16 (single crystal and powder XRD). Refractive indices for LiGaS 2 and LiGaSe 2 are measured over the whole transparency range. Sellmeier equations are fitted and phase-matching conditions for second harmonic generation are calculated. The 1.467-11.72 µm spectral range for the fundamental is covered by LiGaS2 and LiGaSe2. -(ISAENKO, L.; YELISSEYEV*, A.; LOBANOV, S.; TITOV, A.; PETROV, V.; ZONDY, J.-J.; KRINITSIN, P.; MERKULOV, A.; VEDENYAPIN, V.; SMIRNOVA, J.; Cryst.

Laser-induced fluorescence (LIF) spectra of calcified human heart-valve tissue and LIF spectra of macroscopic calcinosis fragments dissected from human heart valves were compared with LIF spectra of pig myocardium tissues. Excitation was provided by an excimer laser with wavelength lambda = 248 nm. Fluorescence bands that were due to mineral and organic tissue components were identified by measurement of LIF spectra of macroscopic fragments of calcified tissues that had been heat treated at 700 degrees C. The studies showed that LIF spectra of calcified tissues include fluorescence emission from tryptophan, collagen, elastin, and a mineral component of tissue, hydroxylapatite. The observed differences in LIF spectra of normal and calcified tissues with different pathologies may result not only from calcification-induced changes in relative collagen and elastin concentrations but also from additional (absent in normal heart tissue) fluorescence of hydroxylapatite. The calcification-induced changes in the LIF spectra of human heart-valve tissues, characterized by a 330/450 nm ratio, were found to be quite appreciable, which suggests that this ratio can be used with LIF measurements to evaluate the degree of heart-tissue calcification.

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We have studied the degradation of photoelectric characteristics of heterojunction solar cell samples based on α-Si:H/Si structures upon irradiation by electrons with an energy of 3.8 MeV and fluences of 1 × 10^12–1 × 10^14 cm^–2. It is shown that the efficiency of the samples of heterojunction solar cell elements under the conditions of AM0 illumination (0.136 W/cm^2) is reduced by 25% at a fluence of 2 × 10^13 cm^–2. This is more than an order of magnitude higher than the critical fluence value achieved previously when silicon solar cells with a p–n junction and an n -type base were irradiated by high-energy electrons.