Development of narrow bandpass filters based on cross cavities for the terahertz frequency range

A narrow bandpass terahertz filter based on cross cavities was developed for four frequencies. The geometric parameters of the cavities for each resonant frequency were calculated, and the filter transmission spectra for the calculated parameters were obtained numerically, analytically, and experimentally. The simulation was carried out in the COMSOL Multiphysics modeling environment using the finite element method. A model of the oscillator circuit was used for the analytical construction of spectra. An experimental sample was fabricated and an experiment was performed using pulse terahertz spectroscopy. The possibility of controlling the spectral characteristics of the filter using two methods—mechanically and by changing the angle of incidence of radiation on the plane of the filter—was studied.