A 0.34-THz Quasi-Optical Resonant Cavity-Based Klystron Amplifier

A klystron amplifier based on Smith–Purcell (SP) radiation and the quasi-optical resonator cavity (QORC) is proposed for terahertz (THz) waves. Benefits from high interaction impedance and simple grating structure of QORC, the proposed klystron amplifier can operate at a low voltage and can achieve a high gain. The verification of the novel concept amplifier is carried out successfully by the particle-in-cell (PIC) simulations of a 0.34-THz klystron amplifier using three QORCs. The results show that with the voltage of 11.5 kV and a current of 70 mA, the klystron amplifier obtains an output power of 11.78 W for an input power of 8 mW, corresponding the gain of 31.7 dB. Besides, in the case of reduced period length of grating, QORC klystron amplifier can operate with the same cavity mode at lower dc power, and the saturated input power is significantly reduced, but the output performance is weakened. The grating of 0.34-THz QORC is fabricated by using computer numerical control (CNC) milling, showing the maximum fabrication deviation of thickness of grating facet less than
$5~\mu \text{m}$
, which proves the fabrication feasibility of the 0.34-THz QORC klystron amplifier.