IR spectroscopic determination of the refractive index of Ag1−xTlxBr1−0.54xI0.54x (0 ⩽ x ⩽ 0.05) crystals

In this paper we examined materials relevant for manufacturing various near- and mid-infrared fiber optical elements: AgBr and - presumably for the first time - AgBr - (TlBr0.46I0.54) up to 5% of TlBr0.46I0.54, produced by hot embossing. Both real and imaginary parts of refractive indices were determined within the wavelength of 3.0-14.0 μm for samples of these materials. An increase of the substituent in AgBr caused a monotonous rise of the refractive index, while for every certain composition, a shift towards longer wavelengths led to its decrease. This dependence was depicted on dispersion curves, which clearly demonstrate that optical fibers, drawn from AgBr - (TlBr0.46I0.54) crystals, can be used within the wide mid-infrared range, since the dispersion coefficient here is minimal and constant. To determine the refractive index at the absorption edge (from 0.465 to 0.484 μm), we scrutinized eleven calculation models, with preferable Moss relation.