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.

Research highlights
► Pure tellurium glasses are stabilized by introducing less than 5% of Se.
► Optical fibres are drawn, transmitting light until 16 μm.
► Fibres evanescent waves’ spectroscopy (FEWS) is carried out in mid-infrared.
► C-Cl bonds, beyond the wavelength of 13 μm, are detected by FEWS.
► The CO2 at 15 μm is detected in the context of the DARWIN mission.