Tapered metallic Photonic Crystal slow wave structure for terahertz vacuum electron devices

An interaction structure employing metallic Photonic Crystals (PhC) to replace the lateral walls of the waveguide enclosure is proposed for terahertz vacuum tubes application. The tapered PhC assures effective confinement of the propagating field and improves the hollowness of the interaction line, thus alleviating the typical issues in the tube assembly.