The Effects of Various Apodization Functions on the Filtering Characteristics of the Grating-Assisted SOI Strip Waveguides

Abstract

In this paper, four apodization functions are proposed for silicon-on-insulator (SOI) strip waveguides with sidewall-corrugated gratings. The effects of apodization functions on the full width at half maximum (FWHM), the side-lobe level, and the reflectivity of the reflection spectrum are studied using the coupled-mode theory (CMT) and the transfer-matrix method (TMM). The results show that applying proposed apodization functions creates very good filtering characteristics. Among investigated apodized waveguides, the apodization functions of Polynomial and z-power have the best performance in reducing side-lobes, where the side-lobe oscillations are entirely removed. Four functions are also used for precise adjustment of the bandwidth. Simulation results show that the minimum and maximum values of the FWHM are 0.74 nm and 8.48 nm respectively. In some investigated functions, changing the apodization parameters decreases the reflectivity which is compensated by increasing the grating length.

Comparative Study of Uniform and Nonuniform Grating Couplers for Optimized Fiber Coupling to Silicon Waveguides

“…Further enhancement of the coupling efficiency has been achieved using apodized waveguide grating structures or an overlay layer [8][9][10][11]. Various apodized grating structures have been also proposed or demonstrated to achieve improved coupling efficiencies of the NGCs.…”