Preparation of High Purity Te-Rich Ge-Te-Se Fibers for 5-15 mu m Infrared Range
Résumé
Te rich glasses in the ternary Ge-Te-Se system are stable against crystallization and remain transparent enough for application in the far infrared beyond 15 μm. Four protocoles of preparation of highly-purified Te-rich Ge-Te-Se glasses are developed and compared. These methods are based on different distillation procedures to remove water, oxides, hydrogen and carbon impurities from glasses. The final residual impurity content in glasses was determined by the IR spectroscopy and laser mass spectrometry. Then, unclad optical fibers were drawn from each synthetized glass. At room temperature, the minimum of attenuation is about 7 dB/m at 10.6 μm whatever the purification procedure, showing that the residual optical losses are intrinsic to the chemical nature of the glasses. On the other hand, at 77 K, the optical losses are lowered to 1 dB/m confirming that losses are mainly due to the high charge carrier concentration inherent to the semi-conducting behavior of these glasses. Finally, this low level of losses is rather a promising news in view of application in space where optical filtering devices working beyond 15 μm are needed.