Compact and low loss silicon-on-insulator rib waveguide 90 degrees bend.

A compact and low loss silicon-on-insulator rib waveguide 90 degrees bend is designed and demonstrated. An interface realized by a trench filled with SU8 at the corner of a waveguide bend effectively reflects incoming light through total internal reflection (TIR). In order to accurately position the SU8-filled trench relative to the waveguide and reduce sidewall roughness of the interface, electron beam lithography (EBL) is employed while inductively coupled plasma reactive ion etching (ICP RIE) is used to achieve a vertical sidewall. The measured loss for TE polarization is 0.32 dB +/- 0.02 dB/bend at a wavelength of 1.55 microm.