Design of tight bends in silicon-on-insulator ridge waveguides

In this work numerical analysis was used to explore ways for reducing bending losses in silicon-on-insulator ridge waveguides. Bending losses in single-mode ridge waveguides with different sizes were calculated. The results obtained were used in a numerical optimization of an S-bend structure. Also, the loss reduction achieved by placing a groove along the side of a bend was determined. Calculations were made for both TE and TM polarizations at 1550nm wavelength. Smaller waveguides were found to cause much smaller bending losses. The groove structure allows the use of ten times smaller bending radii. With the groove, a ridge waveguide with 1.5µm thickness and 75µm bending radius was found to have only 0.7dB loss in a 90° turn, when both bending and junction losses were taken into account. The numerical path optimization of an S-bend halved the total loss in dB.