Full 3D+1 modelling of the tilted-pulse-front setups for single-cycle terahertz generation

TL;DR

This paper presents a comprehensive 3D+1 numerical model for tilted-pulse-front terahertz generation, revealing how beam size and geometry influence the spatio-temporal properties of the generated terahertz pulses.

Contribution

It introduces a detailed 3D+1 simulation approach to better understand and optimize terahertz generation in tilted-pulse-front setups, highlighting spatial effects.

Findings

Terahertz electric field varies strongly with spatial position.

A few-cycle pulse is generated only near the prism apex.

Spatial inhomogeneity affects applications in strong-field physics.

Abstract

The tilted-pulse-front setup utilizing a diffraction grating is one of the most successful methods to generate single- to few-cycle terahertz pulses. However, the generated terahertz pulses have a large spatial inhomogeneity, due to the noncollinear phase matching condition and the asymmetry of the prism-shaped nonlinear crystal geometry, especially when pushing for high optical-to-terahertz conversion efficiency. A 3D+1 (x,y,z,t) numerical model is necessary in order to fully investigate the terahertz generation problem in the tilted-pulse-front scheme. We compare in detail the differences between 1D+1, 2D+1 and 3D+1 models. The simulations show that the size of the optical beam in the pulse-front-tilt plane sensitively affects the spatio-temporal properties of the terahertz electric field. The terahertz electric field is found to have a strong spatial dependence such that a few-cycle pulse is only generated near the apex of the prism. The part of the beam farther from the apex contains a large fraction of the energy but has a waveform that deviates from a few-cycle. This strong spatial dependence must be accounted for when using the terahertz pulses for strong-field physics and carrier-envelope-phase sensitive experiments such as terahertz acceleration, coherent control of antiferromagnetic spin waves and terahertz high-harmonic generation.