An overmoded structure for the narrowband high-power terahertz pulse detection

An overmoded detecting structure for 0.14 THz frequency band based on hot electron effect in semiconductors is proposed in this paper. The novel device consists of two standard waveguides WR10 and WR6, a tapered waveguide, a sensing sample composed of n-type silicon, and a bias constant current source. With sensing sample mounted on the wide wall of WR10, the waveguide WR6 and tapered waveguide are assembled ahead to ensure the basic mode operation of the detector. According to the derived relative sensitivity, a three-dimensional finite-difference time-domain method is used to optimize the structural parameters of the detector with flat frequency response. Numerical results indicate that, while the bias voltage on the sensing element is 10 V, the sensitivity of the optimized detector in linear region is around 2 V/kW with a fluctuation less than 25% in the frequency range 0.13-0.16 THz. Compared with traditional resistive sensor and diode detectors, the detector with overmoded structure shows its special merits for the power measurements of narrowband high-power terahertz pulses.