Small radius bends and large angle splitters in SOI waveguides

Abstract
The silicon/silicon dioxide (Si/SiO2) materials system provides a high index contrast waveguide platform compatible with existing monolithic microelectronic fabrication processes. The large index difference between the Si and SiO2 ((Delta) n approximately equals 2.0) allows the miniaturization of waveguide cross-sectional dimensions: single-mode strip waveguides with 0.2 X 0.5 micrometers cross-sections are possible. Additionally, right angle waveguide bends with radii of 2.0 micrometers can be fabricated with insertion loss of less than 1.0 dB. Bend radii of 250 micrometers or more are required to achieve the same performance in less confined waveguide systems such as GaAs/AlGaAs. The high confinement of the Si/SiO2 system also allows Y-branch power splitters with splitting angles greater than 20 degree(s) to operate with low loss. The combination of small cross- section, small bend radius, and large splitting angle provides a highly compact light guiding technology. Calculations of the loss due to 90 degree(s) bends in these waveguides and preliminary loss measurements for bends from 2.0 to 100.0 micrometers in radius are reported. Y-branch power splitters are analyzed and measurements of branches from 2 degree(s) to 40 degree(s) are presented.