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

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.