Selenium modified GeTe₄ based glasses optical fibers for far-infrared sensing

This study reports on the synthesis of telluride glasses that have transmission far beyond the second atmospheric window and are stable enough toward crystallisation to be drawn into optical fiber. These glasses are based on the GeTe₄ initial composition which has been stabilized by the introduction of few percents of Se and a modified the Te/Ge ratio. In that domain, Ge₂₁Se₃Te₇₆ constitute the optimum composition and some mono index optical fibers have been successfully drawn. It is shown that their optical transparencies extend from 5 to almost 16 μm in the mid-infrared, establishing a record for chalcogenide glass fibers. These fibers have been used to implement Fiber Evanescent Wave Spectroscopy experiments, permitting to detect infrared molecule signatures beyond 12 μm, infrared domain that was unreachable by now. These innovative fibers are also used to detect the broad absorption band of gaseous CO₂ lying from 13 to 16 μm and therefore hold promises in the framework of the Darwin mission of the European Space Agency. Both of these results suggest that these new optical fibers will become essential in the field of infrared remote sensing.