Comparison between strip and rib SOI microwaveguides for intra-chip light distribution

A comparative analysis of the strip and rib geometries guided wave devices (waveguides, bends, mirrors, beam splitters) is performed to realize an optical distribution to several outputs. For the strip structures, the optical losses are strongly sensitive to side-wall roughness due to processing, whereas for slightly etched submicron rib waveguides, optical losses are lower than 0.4 dB/cm. The design, realization and characterization of an H-tree optical distribution from one input to 16 output points using 1 cm long rib waveguides, four compact T-splitters and two mirrors are presented. A 2.6 μW optical power is obtained at each output for a 3 mW input power. This corresponds to an excess loss of 14 dB which seems to be sufficient for an integrated photodetector.