Quasi-Optical Pulse Compressor Featuring Linear Resonant Cavity for Tunable Nanosecond Terahertz Pulse Generation

The quasi-optical (QO) pulse compressor is a promise method to generate amplified high-power nanosecond terahertz (THz) pulse, but its fixed output pulsewidth significantly limits practical applications. To address this limitation, we propose a QO pulse compressor incorporating a linear resonant cavity, enabling continuous tunability of THz pulse widths. By adjusting the optical distance between two terminal mirrors in the linear cavity, the output THz pulsewidth can be precisely tuned with high resolution. Strategic integration of beam-focusing mirrors can significantly extend the pulsewidth tuning range. To counteract gain factor reduction induced by propagation loss variations during optical path adjustment, a double-wafer laser-driven semiconductor switch (LDSS) featuring controllable reflectance serves as the coupler, ensuring critical coupling across the entire tuning range. In simulations and experiments, we investigate the effect of the coupling condition and the optical path adjustment on the gain factor and the pulsewidth tunability. Results demonstrate that within the 230–260-GHz operating frequency band, the output THz pulsewidth is continuously tunable from 3 to 15 ns with subnanosecond resolution, while maintaining a peak gain factor of 15 and values exceeding 7 throughout tuning. This achieved pulsewidth tunability surpasses the state-of-the-art reported performances.