A new compact silicon grating coupler enabling fibre-to-chip light coupling at a minimized taper length is proposed. The proposed coupler, which incorporates a hollow tapered waveguide, converts the spot-size of optical modes from micro- to nano-scales by reducing the lateral dimension from 15 µm to 300 nm at a length equals to 60 µm. The incorporation of such a coupler in photonic integrated circuit causes a physical footprint as small as 81 µm × 15 µm with coupling efficiency and 3-dB coupling bandwidth as high as 72% and 69 nm respectively.

Nanophotonic technologies have attracted a lot of attention to co-develop optical and electronic devices on silicon that further modern optical communications in miniaturization. Optical properties of these miniaturized devices are highly dependent on waveguide geometry and can be tailored for various applications with minor changes in cross-sectional areas. This paper investigates the performance of widely discussed planar, rib and photonic crystal silicon (Si) waveguides by manipulating the dimensions of Si core designed for single mode operation across the 1.2 to 1.6 micron telecommunication bands. Each of the waveguide is studied and compared for a set of properties including effective refractive index, group index, group-velocity dispersion (GVD) and mode loss, with and without narrow bends which can be instrumental in selecting the correct type and geometry of the waveguide required for any specific application.Index Terms-Group velocity dispersion (GVD), mode confinement loss, planar waveguide, rib waveguide, photonic crystal waveguide, photonic nanostructures, silicon Photonics, silicon waveguides, silicon on insulator (SOI).

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