Modeling and measurement of losses in silicon-on-insulator resonators and bends

We present an analytical model to quantify losses in resonators and bends without uncertain contributions from fiber coupling in/out or waveguide cleavage facets. With resonators in add-drop configuration, intrinsic losses are calculated from the free spectral range, through-port extinction and drop-port bandwidth. We fabricated and characterized silicon-on-insulator resonator for loss analysis. At 1.55 mu m, racetrack resonators with a bending radius of 4.5 mu m show intrinsic losses as small as 0.14 +/- 0.014 dB/round-trip. Meanwhile, intrinsic losses increase up to 1.23 dB/ round-trip in the racetrack resonator that has a bending radius of 2.25 mu m. Losses in a 180 degrees bend are estimated as a half of the intrinsic losses in these racetrack resonators, i. e., 0.07 +/- 0.007 dB/ turn for a bending radius of 4.5 mu m and 0.62 dB/turn for a bending radius of 2.25 mu m. Loss in a 90o bend with a radius of 4.5 mu m is determined to be 0.06 +/- 0.006 dB/turn at 1.55 mu m. The losses in 180 degrees or 90 degrees bends are found to be mainly due to the transition loss between waveguide bends and straight waveguides.