title: Increased impedance near cut-off in plasma-like media leading to emission of high-power, narrow-bandwidth radiation.
abstract: Ultra-intense, narrow-bandwidth, electromagnetic pulses have become important tools for exploring the characteristics of matter. Modern tuneable high-power light sources, such as free-electron lasers and vacuum tubes, rely on bunching of relativistic or near-relativistic electrons in vacuum. Here we present a fundamentally different method for producing narrow-bandwidth radiation from a broad spectral bandwidth current source, which takes advantage of the inflated radiation impedance close to cut-off in a medium with a plasma-like permittivity. We find that by embedding a current source in this cut-off region, more than an order of magnitude enhancement of the radiation intensity is obtained compared with emission directly into free space. The method suggests a simple and general way to flexibly use broadband current sources to produce broad or narrow bandwidth pulses. As an example, we demonstrate, using particle-in-cell simulations, enhanced monochromatic emission of terahertz radiation using a two-colour pumped current source enclosed by a tapered waveguide.
authors.affiliation: School of Natural Science, UNIST, Ulsan, 689-798, Korea.
authors.forename: M S
authors.initials: MS
authors.lastname: Hur
authors.affiliation: Scottish Universities Physics Alliance and University of Strathclyde, Glasgow G4 0NG, United Kingdom.
authors.forename: B
authors.initials: B
authors.lastname: Ersfeld
authors.affiliation: Scottish Universities Physics Alliance and University of Strathclyde, Glasgow G4 0NG, United Kingdom.
authors.forename: A
authors.initials: A
authors.lastname: Noble
authors.affiliation: Department of Physics and Photon Science, GIST, Gwangju, 500-712, Korea.
authors.forename: H
authors.initials: H
authors.lastname: Suk
authors.affiliation: Scottish Universities Physics Alliance and University of Strathclyde, Glasgow G4 0NG, United Kingdom.
authors.forename: D A
authors.initials: DA
authors.lastname: Jaroszynski