The study of a Bragg grating based on hybrid plasmonic waveguides

Abstract

A Bragg grating based on a hybrid plasmonic waveguide (HPW) is proposed and investigated. This HPW's structure consists of an air gap sandwiched between a silicon waveguide and a silver grating with its reflective ridges towards the silicon waveguide. The width of the air gap varies periodically because of the ridges and grooves of the silver grating, which results in the periodical modulation of the HPW's effective refractive index along the light propagation direction. A Bragg grating is shown with an extinction ratio of the transmission spectrum 24dB, a transmittance of 85%, and a resonance peak 3dB bandwidth 19nm in the HPW consisting of a silicon waveguide with a cross-section of dimensions 350nm×350nm, and a silver grating of ridge height 50nm, period 325nm, and length 40μm. The relation between the resonance peak central wavelength and the period of the grating is found to be nonlinear and is formulated. There should be a tradeoff between the high extinction ratio of the transmission spectrum and low loss in the optimization of the HPW parameters.