Spectrally shaped THz pulses from tapered dielectric waveguides

TL;DR

This paper presents the design of tapered dielectric waveguides capable of generating spectrally shaped THz pulses up to 1 THz, tailored for accelerator-based pump-probe applications like the European XFEL.

Contribution

It introduces custom waveguide geometries with tapered layers or radii to produce spectrally tailored THz pulses, advancing THz source development for accelerator facilities.

Findings

Achieved generation of flat-top and Gaussian THz pulses up to 1 THz.

Demonstrated scalability of spectral content to higher frequencies.

Provided design principles for spectrally shaped THz pulse generation.

Abstract

In order to exploit the complete scientific potential of user-oriented accelerator facilities, it is necessary to provide adequate pump sources to enable pump-probe science. The users of the European XFEL have requested a THz pump source matching the X-ray repetition rate (10 Hz burst mode with up to 2700 bunches per burst) with a wide range of properties. The quest for suitable THz sources is thus a major development goal. The EuXFEL R\&D project STERN is exploring beam-based radiation generation methods using Cherenkov waveguides to satisfy these user requirements. In this work, custom waveguide geometries are designed to generate a THz pulse with arbitrary spectral content. The layer-thickness or inner radius of a wakefield structure is tapered to generate flattop or Gaussian pulses up to $1 \ \mathrm{THz}$, which can be scaled to higher frequencies.