Analysis of dispersion properties of photonic crystal slab

Abstract

Line-defect waveguides in photonic crystals are receiving considerable attention because their waveguiding mechanism is fundamentally different from that of conventional dielectric waveguides, such as optical fibres, which rely on total internal reflection. It has various unique properties which cannot be provided by conventional waveguides such as realization of sharp bends and group velocity dispersion characteristics that differ greatly from conventional waveguides. This structure is based on silicon photonics which allow different optical components to connect each other using silicon waveguide to establish very fast communication between circuit boards, between chips on a board, or even within single chips.

The present work aims at the designing, simulation and analysis of a structure on SOI based on hexagonal lattice of two dimensional photonic crystal with flat dispersion over a large wavelength band, low propagation loss and polarization dependent single mode photonic crystal waveguide. By varying various parameters such as diameter of air holes (d), lattice constant (a) analysis has been done for an optimum profile and low propagation loss is realized. At photonic waveguide parameters, thickness of Si is 0.3 µm, thickness of SiO2 is 1.0 µm, diameter of air-holes (d) is 0.44 µm, and lattice constant (a) is 0.9 µm at the wavelength of 1.55 µm. The low propagation loss is estimated to be of 3.6 dB/ mm. Although the largest negative dispersion value of 19.9x104 ps/nm km is calculated for d= 0.44 μm and a= 0.5 µm but desired structure has been achieved at d= .44 μm and a= 1 µm of flat dispersion in a range of 1.375x104 ps/nm km to 0.913x104 ps/nm km with the wavelength range of 1.55 µm to 1.65 μm. The characteristics of both the TE and TM like polarization exhibit periodicity at a= 0.8 µm and a= 1.0 µm of lattice constant the effective group index for both polarizations coincide at the wavelength of 1.55 µm. Polarization dependent loss and polarization dependent dispersion characteristics are also analysed with proposed structure. Such waveguides can also find applications in generation of slow light which is a promising solution for buffering and time-domain processing of optical signals and also offers the possibility for spatial compression of optical energy and the enhancement of linear and nonlinear optical effects.