Radiation of a Charge Exiting Open-Ended Waveguide with Dielectric Filling

TL;DR

This paper presents an analytical solution for electromagnetic radiation emitted by a charge exiting a dielectric-filled open-ended waveguide, with applications in Terahertz radiation generation and validation through numerical simulations.

Contribution

The authors develop a rigorous analytical method using residue calculus to solve the electromagnetic problem involving dielectric-filled waveguides, validated by numerical simulations.

Findings

Excellent agreement between analytical and CST simulation results.

Cherenkov radiation analysis in dielectric and vacuum regions.

Potential for efficient Terahertz radiation generation using high-order modes.

Abstract

We consider a semi-infinite open-ended cylindrical waveguide with uniform dielectric filling placed into collinear infinite vacuum waveguide with larger radius. Electromagnetic field produced by a point charge or Gaussian bunch moving along structure's axis from the dielectric waveguide into the vacuum one is investigated. We utilize the modified residue-calculus technique and obtain rigorous analytical solution of the problem by determining coefficients of mode excitation in each subarea of the structure. Numerical simulations in CST Particle Studio are also performed and an excellent agreement between analytical and simulated results is shown. The main attention is paid to analysis of Cherenkov radiation generated in the inner dielectric waveguide and penetrated into vacuum regions of the outer waveguide. The discussed structure can be used for generation of Terahertz radiation by modulated bunches (bunch trains) by means of high-order Cherenkov modes. In this case, numerical simulations becomes difficult while the developed analytical technique allows for efficient calculation of the radiation characteristics.