Low-Loss Silicon Waveguides and Grating Couplers Fabricated Using Anisotropic Wet Etching Technique

We report low-loss silicon waveguides and efficient grating coupler to couple light into them. By using anisotropic wet etching technique, we reduced the side wall roughness down to 1.2 nm. The waveguides were patterned along the [112] direction on a [110] silicon-on-insulator substrate. The waveguide boundaries are decided by the [111] planes, which are normal to the [110] surface. Fabricated waveguides show minimum propagation loss of 0.85 dB/cm for TE polarization and 1.08 dB/cm for TM polarization. The fabricated grating couplers show coupling efficiency of −4.16 dB at 1570 nm with 3 dB bandwidth of 46 nm.