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

摘要

We propose and experimentally demonstrate a tunable band-notched line-defectwaveguide in a surface-wave photonic crystal, which consists of a straightline-defect waveguide and side-coupled defect cavities. A tunable narrowstopband can be observed in the broadband transmission spectra. We alsodemonstrate that both the filtering levels and filtering frequencies of theband-notched line-defect waveguide can be conveniently tuned through changingthe total number and the pillar height of the side-coupled defect cavities. Theband-notch function is based on the idea that the propagating surface modeswith the resonance frequencies of the side-coupled defect cavities will betightly localized around the defect sites, being filtered from the waveguideoutput. Transmission spectra measurements and direct near-field profilesimaging are performed at microwave frequencies to verify our idea and design.These results may enable new band-notched devices design and provide routes forthe realization of tunable surface-wave filters on a single metal surface.