Fabrication and characterization of straight and compact S-bend optical waveguides on a silicon-on-insulator platform

Straight and S-bend rib waveguide structures with a novel design have been fabricated and characterized on a silicon-on-insulator (SOI) platform. For a typical straight rib waveguide, the single-mode waveguide at lambda approximately 1550 nm has been verified by measuring the near-field output with an IR camera, and a nearly polarization-independent mode size is found to be approximately 10 microm x 4.5 microm. The waveguide loss has been estimated from low-finesse Fabry-Perot transmission characteristics, and a typical value of approximately 0.5 dB/cm is obtained. It is also shown experimentally that the bending radius of an asymmetrically etched S-bend waveguide can be ten times smaller than that of conventional symmetrically etched S-bend waveguides for similar optical losses. These bend waveguides (bending radii of approximately 1500 microm) are found to be low loss (<2.5 dB) and nearly polarization independent.