Design and fabrication of As₂Se₃ chalcogenide waveguides with low optical losses

In this paper, we report the fabrication and characterization of chalcogenide-based planar waveguides for possible applications in broadband light sources and/or biochemical sensing. ${{\rm Ge}_{11.5}}{{\rm As}_{24}}{{\rm Se}_{64.5}}$Ge_11.5As₂₄Se_64.5 film as bottom cladding followed by another layer of ${{\rm As}_2}{{\rm Se}_3}$As₂Se₃ was deposited on a thermally oxidized silicon wafer using thermal evaporation, and the waveguides were patterned directly on the ${{\rm As}_2}{{\rm Se}_3}$As₂Se₃ layer by UV exposure followed by inductively coupled plasma dry etching. The device structure was optimized by using commercial software (COMSOL Multiphysics) based on complete vector finite components, and the fundamental mode of the waveguide was calculated. By optimizing the geometry of the waveguide, the zero dispersion wavelength was shifted to a short wavelength (at $\sim{2}.{3}\;\unicode{x00B5} {\rm m}$∼2.3µm), which facilitates supercontinuum generation with shorter wavelength pump source. The insertion loss of the rib waveguides with different widths was measured using the cut-back method, and the best propagation loss at 1550 nm was 1.4 dB/cm.