Tunable band-notched line-defect waveguide in a surface-wave photonic crystal

TL;DR

This paper presents a tunable band-notched waveguide in a surface-wave photonic crystal, enabling adjustable filtering frequencies and levels through structural modifications, verified by microwave experiments.

Contribution

It introduces a novel tunable band-notched waveguide design with adjustable filtering properties using side-coupled defect cavities in a surface-wave photonic crystal.

Findings

Tunable narrow stopband observed in transmission spectra.

Filtering levels and frequencies can be adjusted by changing defect cavity parameters.

Experimental verification through microwave measurements and near-field imaging.

Abstract

We propose and experimentally demonstrate a tunable band-notched line-defect waveguide in a surface-wave photonic crystal, which consists of a straight line-defect waveguide and side-coupled defect cavities. A tunable narrow stopband can be observed in the broadband transmission spectra. We also demonstrate that both the filtering levels and filtering frequencies of the band-notched line-defect waveguide can be conveniently tuned through changing the total number and the pillar height of the side-coupled defect cavities. The band-notch function is based on the idea that the propagating surface modes with the resonance frequencies of the side-coupled defect cavities will be tightly localized around the defect sites, being filtered from the waveguide output. Transmission spectra measurements and direct near-field profiles imaging are performed at microwave frequencies to verify our idea and design. These results may enable new band-notched devices design and provide routes for the realization of tunable surface-wave filters on a single metal surface.