We investigate the loss mechanism in three-moded multimode-interference couplers that are the building blocks of a compact and low-loss waveguide crossing structure. Broadband silicon waveguide crossing arrays with <0.01  dB insertion loss per crossing are proposed using cascaded multimode-interference couplers, where lateral subwavelength nanostructures are used to reduce the insertions loss. ...

We experimentally demonstrate broadband waveguide crossing arrays showing ultralow loss of 0.0 4dB/crossing (0.9%) on average and converging to 0.033 dB/crossing (0.075%) matching theory and cross-talk suppression over 35 dB in a CMOS-compatible geometry. The principle of operation is the tailored excitation of a low-loss spatial Bloch wave formed by matching the periodicity of the crossing arr...

We present general criteria for crossing perpendicular waveguides with nearly 100% throughput and 0% cross talk. Our design applies even when the waveguide width is of the order of the wavelength. The theoretical basis for this phenomenon is explained in terms of symmetry considerations and resonant tunneling and is then illustrated with numerical simulations for both a two-dimensional photonic...

Increasing scope and applications of integrated optics necessitates the development of automated techniques for physical design of optical systems. A key area of integrated optic design is waveguide routing, which currently lacks the level of automation found in VLSI design. Unlike VLSI, where signal nets are routed with metal layers and vias, integrated optics is a planar technology and lacks ...

We design an intersection for crossing waveguides in triangular lattice photonic crystals with cross-talk smaller than 10(-5). The cross-talk to the transverse waveguides is suppressed by symmetry mismatch between the cavity mode and the waveguide mode or by the mode-gap effect induced by air hole radius modulation of the waveguides. The transmission behavior of the crossing waveguides are illu...