Left: cross-section view of the Y-junction geometry. The high-index strip waveguide is bounded by As₂Se₃, As₂S₃ and air. Examples of refractive indices at 6, 8, 10, and 12 μm used in this study are n = 2.788, 2.783, 2.777, 2.774 for As₂Se₃ and n = 2.403, 2.394, 2.381, 2.364 for As₂S₃. Right: theoretical spatial distribution of the electric field for the TE_0,0 fundamental mode superimposed on the waveguide geometry. The vertical scale ranges from high (violet) to low (yellow) intensity.