Determining small refractive index contrast in chalcogenide-glass pairs at mid-infrared wavelengths

A two-composition thin film (Ge20Sb10Se70/Ge20Sb10Se67S3 atomic%core/cladding glasses) was fabricated using a hot-fibre-pressing technique in which both glasses follow the same post-fibre processing. A simple approach is proposed that uses normal incidence transmission spectra to determine their refractive index contrast over the wavelength range from 2 to 25 μm with an error of less than _ 0.002. Using an improved Swanepoel method, the calculated numerical aperture of these two compositions was within _ 0.011 of that obtained from prism minimum deviation measurements. Results show that introducing 3 atomic % S into the Ge-Sb-Se glass system lowered the refractive index and blue-shifted the visible optical bandgap, the far-infrared fundamental vibrational absorption bands and the zero-dispersion wavelength

High purity Ge-Sb-Se/S step index optical fibers

Chalcogenide glasses are a promising group of materials for remote sensing applications. Two compositions from the Ge-Sb-Se/S system are investigated as core and cladding glasses in a step index fiber (SIF). Following thermomechanical and refractive index measurements, mid-infrared (MIR) light guiding is demonstrated through an 8 m length of SIF with a Ge20Sb10Se70 at. % core and Ge20Sb10Se67S3 at. % cladding. Using a single distillation procedure, Ge20Sb10Se70 at. % glass fibers are shown to have low optical loss across the 2 to 10 µm wavelength range with the lowest baseline loss shown as 0.44 dB/m at 6.4 µm