Serpentine low loss trapezoidal silica waveguides on silicon

We report the fabrication and characterization of straight and serpentine low loss trapezoidal silica waveguides integrated on a silicon substrate. The waveguide channel was defined using a dual photo-lithography and buffered HF etching and isolated from the silicon substrate using an isotropic silicon etchant. The waveguide is air-clad and thus has a core-cladding effective index contrast of approximately 25%. Measured at 658, 980 and 1550 nm, the propagation loss was found to be 0.69, 0.59, and 0.41 dB/cm respectively, with a critical bending radius less than 375 μm. The waveguide's polarization behavior was investigated both theoretically and experimentally. Additionally, the output power shows a linear response with input power up to 200 mW.