Resonance-mode-induced beating effect for THz wave generation and principal demonstration

We present a method of terahertz (THz) wave generation in the complete THz band that harnesses resonance modes within high-quality-factor photonic-crystal resonators. In the proposed method, the input infrared “single-frequency” wave and the resonance mode induced efficiently in the resonator generate a beat note of THz frequency, and the beat note is converted to an independent THz radiation wave with the help of an amplitude demodulator, which provides high power-conversion efficiency (PCE). The theoretical PCE is a 22.93 % half-wave-rectification amplitude demodulator without considering the insertion loss. Through simulations, we demonstrate the feasibility of our approach of inducing a resonance mode from a conventional “single-frequency” wave and using the induced resonance mode to beat with the input source wave with PCE of 24.03 % in agreement with the theoretical PCE value by half-wave-rectification demodulation. Such a high PCE can be obtained only at a certain frequency. The mechanism of the proposed method is further demonstrated experimentally in the microwave band. The proposed method is a general method that can be applied to frequency conversion of all kinds of waves, showcasing its potential across various applications in electronics, optics, acoustics, and beyond. We expect to overcome many future challenges in terahertz technology because of its high efficiency and miniaturization. Furthermore, our findings pave the way for efficient frequency manipulation with broad implications in signal processing, detection, and communication systems.