Large-mode-area infrared guiding in ultrafast laser written waveguides in Sulfur-based chalcogenide glasses

Current demands in astrophotonics impose advancing optical functions in infrared domains within embedded refractive index designs. We demonstrate concepts for large-mode-area guiding in ultrafast laser photowritten waveguides in bulk Sulfur-based chalcogenide glasses. If positive index contrasts are weak in As₂S₃, Ge doping increases the matrix rigidity and allows for high contrast (10^?3) positive refractive index changes. Guiding with variable mode diameter and large-mode-area light transport is demonstrated up to 10μm spectral domain using transverse slit-shaped and evanescently-coupled multicore traces.