Low-loss chalcogenide waveguides on lithium niobate for the mid-infrared

We demonstrate low-loss chalcogenide (As(2)S(3)) waveguides on a LiNbO(3) substrate for the mid-IR wavelength (4.8 μm). Designed for single-mode propagation, they are fabricated through photolithography and dry-etching technology and characterized on a mid-IR measurement setup with a quantum cascade laser. For straight waveguides, propagation loss as low as 0.33 dB/cm is measured and low-loss bends on the order of 100 μm are simulated, with measurement results showing <3 dB for a 250 μm bend radius. The coupling efficiency is estimated to be 81%. In addition, the influences of variations in width and bend radius are also investigated.