Design for beam splitting components employing silicon-on-insulator rib waveguide structures

[[abstract]]© 2005 Optical Society of America - We present a new design for beam splitting components employing a silicon-on-insulator rib waveguide structures. In the new design, a high-index thin-film layer is deposited in the rib section to reduce the wave field dispersive tails in the slab section and accordingly render the mode field a confined spot. This in turn improves the beam splitting performance of some conventional waveguide components such as y branches and multimode interference couplers (MMICs), in terms of the excess loss, fiber coupling loss, and compactness of these components. For a 1×2 y-branch beam splitter, the excess loss can be as small as 0.43 dB in the new design, which is much lower than that for a conventional rib waveguide structure (which is 1.28 dB). For a 1×2 MMIC in our example, the new rib waveguide structure presents an excess loss of 0.064 dB for the TE mode and 0.046 dB for the TM mode, with negligible nonuniformity in dimensions of 30 μm × 1040 μm, whereas its counterpart (i.e., the one with the same dimensions but without a thin-film layer) presents an excess loss of [similar to] 0.86 dB for both modes. A conventional MMIC must have dimensions larger than 70 μm × 5650 μm to maintain almost the same low excess loss. © 2005 Optical Society of America.[[department]]電機工程學