Single-Polarization Waveguiding by Low-Index Strips on the Surface of Chalcogenide Glass Film

In this paper, we propose and demonstrate a simple chalcogenide glass (ChG) waveguide structure, which is composed of a low refractive-index strip on the surface of the planar ChG film. Theoretical analysis shows that it supports single quasi-TE mode transmission at 1.55 μm with high third-order nonlinearity and negligible bending loss if the bending radius is higher than 60 μm. Then, the ChG waveguide is fabricated and measured. For the waveguide sample with a ChG film of 180 nm in thickness, the measured attenuation of the quasi-TE mode is 0.4 dB/cm at 1.55 μm. Meanwhile, the extinction ratio between the two polarization modes in the waveguide sample of 10 mm in length is higher than 25 dB over a region of 80 nm at 1.55 μm. For the waveguide sample with similar length and a smaller ChG film thickness (150 nm), the extinction ratio increases to 35 dB. These results demonstrate its property of low-loss single-polarization transmission. It provides a simple way to realize high-quality ChG waveguides, which have great potential on integrated nonlinear optical devices.