Realization of large reflective surface of silica-waveguide turning corner with strategic deep-trenching

In this work, a strategic deep trenching with theoretical optimization is adopted to reach a successful reflective effect of WTC structure. The experimental results are within the reasonable range. We select the SOS refractive index difference of 0.75%, waveguide core size of 5.5 μm × 5.5 μm. We know, only the trench bottom is at the same depth as the waveguide core, the side-wall can reflect the guided-mode from an input waveguide to an output waveguide, so set the trenching depth of 26 μm, which is realized with the inductively coupled plasma (ICP) dry etching technique. Such a deep trenching process has to face the critic challenge in the bottom position and angle of trench side-wall as well as the roughness. At 1.55 μm wavelength, we have experimentally observed the output guided-mode and then measure the average optical loss of each WTC structure is 11 dB, implying that an optical reflective efficiency of 8% has been reached.