Optical properties of Ge–Te–Ga doping Al and AlCl3 far infrared transmitting chalcogenide glasses

The development of far infrared optical devices requires optical materials transmitting light far beyond 20 μm. In this paper, two series of far-IR transmitting glasses including Ge–Te–Ga–Al and Ge–Te–Ga–AlCl3 were synthesized by melting–quenching method. Their thermal stability and IR transmitting property were investigated too. These glasses have wide infrared transmission region from 1.8 to 20 μm, and the absorption peak of oxide in the 15–20 μm region disappeared in the Fourier-transform infrared (FTIR) spectra when Al or AlCl3 was added into the Ge–Te–Ga system. The Ge–Te–Ga–Al glass samples show good thermal stability and high resistance to crystallization. Among these glasses, the (Ge0.15Te0.75Ga0.1)94Al6 glass has the highest glass transition temperature Tg (196.3 °C), and the Ge15Te75Ga6Al4 glass has the largest △T (126.2 °C). In addition, the △T values of the Ge–Te–Ga–AlCl3 glass samples are all over 100 °C and have small fluctuation, which are acceptable for practical application.