Tunable Flat-Top Filtering Response in Cascaded Resonant Waveguide Gratings

Jinhua Hu,Long Zhang,Jun Zou,Xiu-Hong Liu,Jiuzhou Yu,Jijun Zhao

doi:10.1109/jphot.2021.3067032

Jinhua Hu, Long Zhang + Show 4 more

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The applicability of resonant waveguide grating (RWG)-based structures as filters to control the spectral response in an optical communication system is investigated. A new physical model for the structure is established on the basis of the Fabry-Pérot (FP) etalon model and coupled leaky mode theory (CLMT). It is found that the flat-top spectral response of the filter is achieved by the combined effect of the guided-mode resonance of an RWG and its Fabry-Pérot resonance (FPR). The bandwidth-tunable spectral response of the filter can be varied according to the change in the eigenvalues of the RWG by changing the structural parameters such as strip width of the grating and incident angle. The flat-top and bandwidth-tunable RWG-based resonant filter is a promising application for high-performance optical communication systems.

Highlights

Resonant waveguide gratings (RWGs) based on guided-mode resonance have been widely studied owing to their simple structure and excellent performance [1]
A single-layered RWG is applied as an optical filter because of the resonant coupling of an incident light wave to a leaky waveguide mode [6]; it was found that the Lorentzian-type spectral response in a single RWG hindered its further application in optical communications
In accordance with previous studies, we considered a single RWG composed of silicon grating layer and silica substrate to be a single-mode lossless resonator

Summary

Introduction

Resonant waveguide gratings (RWGs) based on guided-mode resonance have been widely studied owing to their simple structure and excellent performance [1]. They are utilized in many functional devices such as optical filters [2], optical sensors [3], absorbers [4], and ultra-broadband reflectors [5]. A single-layered RWG is applied as an optical filter because of the resonant coupling of an incident light wave to a leaky waveguide mode [6]; it was found that the Lorentzian-type spectral response in a single RWG hindered its further application in optical communications. The flat-top filters with tunable bandwidth were designed by the theoretical FP-CLMT model and identified by employing the rigorous coupled-wave analysis (RCWA) method [19]

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