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Optical spectra were investigated in a spectral range of (300 - 700) nm for CuAlS2 single crystals. Transmission and wavelength modulated transmission spectra demonstrated presence of some impurity absorption bands in the region of optical transparency of crystals. Optical functions (real and imaginary components of the dielectric function, refractive index and extinction coefficient) have been calculated from the optical reflection spectra by means of the Kramers-Kronig relations. A strong anisotropy and birefringence have been revealed for CuAlS2 crystals. Two isotropic points have been found in (100) oriented platelets around 380 nm and 530 nm. The position of the isotropic point around 530 nm was found to be strongly influenced by the technological conditions of crystal growth and platelet thickness, it being situated at 535 nm for a platelet with thickness of 223 μm. An optical band-pass filter was constructed with such a platelet placed between two Gran-Thompson prism crossed polarizers.

The anisotropy of reflection, transmission and wavelength modulated reflection and transmission optical spectra of ZnAl 2 Se 4 crystals doped by cobalt were investigated at 10 and 300 K. Intersections of refractive indices spectral dependences of ordinary and extraordinary waves (isotropic wavelengths λ 0 , λ 01 , λ 02 and λ 03 ) were revealed in the region of electron transitions from Co 2+ ions and in the depth of absorption band ( λ 04 , λ 05 , λ 06 and λ 07 ). It was found, that the spectral dependence Δ n = n (E⊥c)− n (E||c) intersects the zero axis in all values of isotropic wavelengths as in transmission region and in the depth of absorption band. The bands observed in reflection spectra of crystals in parallel and crossed polarizers at isotopic wavelengths have half-widths around 7–15 Å. Refractive indices in isotropic wavelengths change in 10 1 –10 3 times. Narrow-band filters of different wavelengths could be created on the base of ZnAl 2 Se 4 crystals doped by cobalt. [ABSTRACT FROM AUTHOR]