The interference of birefractive waves in ZnAl2Se4:Co2+ crystal

The anisotropy of reflection, transmission and wavelength modulated reflection and transmission optical spectra of ZnAl2Se4 crystals doped by cobalt were investigated at 10 and 300 K. Intersections of refractive indices spectral dependences of ordinary and extraordinary waves (isotropic wavelengths λ0, λ01, λ02 and λ03) were revealed in the region of electron transitions from Co2+ ions and in the depth of absorption band (λ04, λ05, λ06 and λ07). It was found, that the spectral dependence Δn=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 101-103 times. Narrow-band filters of different wavelengths could be created on the base of ZnAl2Se4 crystals doped by cobalt.