Efficient, 0.35-THz Overmoded Oscillator Based on a Two-Dimensional Periodic Surface Lattice

We present the theory, design, and numerical modeling of a cylindrical, two-dimensional periodic surface lattice (2D-PSL) intended for use as the interaction region of an electron beam-driven, pulsed source. The production of 1.95-MW peak, pulsed 0.35-THz radiation with an electronic efficiency of 24% is reported. Mode selection in the oversized cavity, where the diameter D is almost
$3.5\times $
larger than the operating wavelength
$\lambda $
, is achieved by coupling volume and surface fields to form a coupled cavity eigenmode. We demonstrate the advantages (including enhanced output power and improved spectral purity) of using a 2D-PSL over a simpler 1-D structure. The cylindrical
${D}/\lambda \sim {3.5} 2\text{D}$
-PSL demonstrates the “proof-of-principle” high-order mode coupling with the potential to increase
${D}/\lambda $
to values of 20 or more for the realization of CW 2D-PSL sources or very powerful pulsed sources. The theory is applicable over a broad frequency range.