Terahertz multichannel notch filter consisting of four T-shaped cavities based on parallel-plate waveguide

Lujing Xing,Qing Cao,Kai Wang,Huifang Zhang

doi:10.1063/1.5057720

Abstract

We propose herein a terahertz (THz) multichannel notch filter consisting of four T-shaped cavities based on a parallel-plate waveguide (PPWG). For such devices, the resonance frequency depends on the separation b of the PPWG and the width w of the grooves. The full width at half maximum (FWHM) of the resonance peak in the power-transmission spectrum varies with the ratio w/b and the resonance frequency f0. When the ratio increases, the resonance frequency redshifts and the FWHM widens. The successive passage of THz waves through the four PPWG-based T-shaped cavities reveals four resonance frequencies. In other words, the device serves as a tunable monochromatic THz multichannel notch filter. Optimizing the THz multichannel notch filter diminishes the effect of the undesired weak resonant modes and gives a smooth power-transmission spectrum. To better display the multichannel notch filter, the electrical-field distribution at four resonance frequencies are shown. Finally, the optimized THz multichannel notch filter operates not only in the lower THz range but also in the higher THz range. This filter may have potential applications in optical communications and wavelength division multiplexing.

Highlights

Research in terahertz (THz) radiation has led to many applications of THz waves in fields such as basic science, security, and astronomy.[1,2,3,4] Recently, THz waveguides have attracted considerable interest.[5,6,7,8,9] One example is the parallel-plate waveguide (PPWG), which has been intensively studied because of its low loss and low dispersion
A narrow dip appears in the transmission spectrum of a THz wave that passes through the PPWG with an embedded groove;[10] Chen et al call this resonant mode the “fundamental cavity mode.”[11]. Many resonant-cavity-PPWG designs have been proposed, such as the T-shaped cavity, Bragg gratings, periodic grooves.[12,13,14,15]
This paper presents a THz multichannel notch filter consisting of four T-shaped cavities based on a PPWG

Summary

INTRODUCTION

Research in terahertz (THz) radiation has led to many applications of THz waves in fields such as basic science, security, and astronomy.[1,2,3,4] Recently, THz waveguides have attracted considerable interest.[5,6,7,8,9] One example is the parallel-plate waveguide (PPWG), which has been intensively studied because of its low loss and low dispersion. To diminish the effect of the undesired weak resonant modes and obtain a smooth power-transmission spectrum, three stubs are fixed to the upper plate between adjacent T-shaped cavities. This weakens the intensity of the undesired resonant modes and reduces the fluctuation from 0.27 to 0.03. The optimized THz multichannel notch filter operates in the lower THz frequency range, and in the higher THz frequency range. This filter may have potential applications in optical communications and wavelength division multiplexing

ANALYSIS OF ONE-CHANNEL STRUCTURE

Initial multichannel structure

Optimized multichannel structure

Findings

CONCLUSIONS