CFDTD PIC Simulation of a Dielectric-Loaded Rectangular Waveguide for THz Wave Generation

The micro-fabrication of small planar or rectangular waveguide components for use at very high frequencies in millimeter and up to THz wave ranges has attracted a lot of attention in recent decades due to advanced semiconductor manufacturing technologies. A homogenous metallic waveguide is a fast wave structure while a slow wave structure (SWS) can be obtained with employing a corrugation or dielectric filling in the waveguide. For a dielectric loaded waveguide, the normal modes are not, in general, either pure transverse electric (TE) or transverse magnetic (TM) modes, but rather combinations of these modes, namely longitudinal section electric (LSE) and longitudinal section magnetic (LSM) modes having no E and H components normal to the interface, respectively. It had been proposed to use a dielectric-loaded rectangular waveguide as an accelerating structure. In this work, we propose to use the partially filled rectangular waveguide as a SWS for THz wave generation (reversed acceleration) since the same beam wave interaction can be employed. The field analysis of the SWS is conducted using a conformal finite-difference time-domain (CFDTD) method and the corresponding dispersion relations of TE, TM, LSE, and LSM modes are calculated. The beam wave interaction for THz generation is studied using the 3-D CFDTD particle-in-cell simulations. The detailed simulation model and calculation results will be presented.