Exploration of a Kilowatt-Level Terahertz Amplifier Based on Higher-Order Mode Interaction

The parameters for a kilowatt-level high-power terahertz amplifier were explored based on the higher-order mode and extended-interaction mechanism. It has been demonstrated that the antisymmetric electrical field mode (TM
₂₁
) has a unique advantage in achieving high power. Physical factors on power extraction were studied. In particular, the heavily reduced
${Q}_{{0}}$
has a great effect on the coupling characteristic as well as the output power. It is found that the critical coupling state, i.e.,
${Q}_{e} = {Q}_{{0}}$
, defines an upper limit of the power that can be extracted from the output circuit. The design of a complete interaction circuit was accomplished. The particle-in-cell (PIC) simulations showed that a saturated power of 1.2 kW can be achieved at 220 GHz with a voltage of 45 kV and a total current of
$2\times0.6$
A where two beams were used. The saturated gain is over 30 dB with a 3-dB bandwidth of
$\sim 400$
MHz.