Optical properties of the zinc-tellurite glasses doped with Cr3+ ions

The zinc-tellurite glasses doped with Cr ³⁺ ion have been synthesized using orthotelluric acid, zinc nitrate, and ammonium dichromate as raw materials. According to the yielded results, Cr ³⁺ ions in the spectral range from 0.3 to 2.8 µm demonstrate two intense broad bands with maxima 454 and 650 nm, corresponding to the transitions ⁴A _2g(F) → ⁴T _1g(F) and ⁴A _2g(F) → ⁴T _2g(F). For the studied wavelength range the spectral dependence of the specific coefficient of Cr ³⁺ allows establishing the minimum chromium content for achieving the determined level of optical losses in glasses. The electron paramagnetic resonance spectra of the doped glasses demonstrate that ions Cr ³⁺ are presented both in the isolated ions and in Cr ³⁺−Cr ³⁺ paired in the distorted octahedral site. The optical band gap, Urbach energies, the crystal field and Racah parameters of the prepared glasses have been evaluated.