Volume and surface mode coupling experiments in periodic surface structures for use in mm-THz high power radiation sources

A J Maclachlan,A W Cross,A D R Phelps,C W Robertson

doi:10.1063/1.5020542

Abstract

Planar Periodic Surface Lattice (PSL) structures of different configurations have been designed, fabricated and measured in the 140-220 GHz frequency band. Surface mode resonances are observed in ‘mesh’ PSL structures. We establish that, when mounted on suitable metal-backed dielectric substrates, PSLs exhibit ‘mode-locked’ coherent cavity eigenmodes formed from coupled volume and surface modes. The ‘proof-of-principle’ coupling of volume and surface modes and concept of mode selection in a large cavity, which can lead to the innovation of high power mm-THz radiation sources, is demonstrated. Evidence of coupled eigenmode formation in a 0.64 mm planar PSL measured at 325-500 GHz is presented, verifying the scalability of this work. Excellent agreement between numerical modelling and experiment is reported.

Highlights

Volume and surface mode coupling experiments in periodic surface structures for use in mm-THz high power radiation sources
When mounted on dielectric substrates, the planar Periodic Surface Lattice (PSL) considered in this work, can support both surface and volume fields
While it is possible to develop a high-power radiation source based on a metal planar PSL combined with an electron sheet beam, planar PSLs, especially those mounted on dielectric substrates, are not intended for use within electron-beam-driven sources

Summary

Introduction

Volume and surface mode coupling experiments in periodic surface structures for use in mm-THz high power radiation sources. The dispersion relation calculated using the AKS Eigenmode Solver of CST Microwave Studio (CST MWS) in Fig. 2 shows coupled volume and surface fields in a planar PSL with period dz =1.74 mm and corrugation depth ∆r =35 μm, mounted on a 0.76 mm copper-backed substrate.

Results

Conclusion