Spatiotemporal control of two-color terahertz generation

TL;DR

This paper demonstrates how spatiotemporal structuring of two-color laser pulses can precisely control the emission angle, focus, and spectrum of generated terahertz radiation, enabling highly focused on-axis THz sources.

Contribution

It introduces a method to manipulate THz emission properties using programmable spatiotemporal laser pulse shaping, a novel approach for THz source control.

Findings

Controlled THz emission angle and spectrum achieved

Sub-luminal intensity peaks enable on-axis THz focusing

Programmable pulse shaping allows precise THz emission control

Abstract

A laser pulse composed of a fundamental and properly phased second harmonic exhibits an asymmetric electric field that can drive a time-dependent current of photoionized electrons. The current produces an ultrashort burst of terahertz (THz) radiation. When driven by a conventional laser pulse, the THz radiation is emitted into a cone with an angle determined by the dispersion of the medium. Here we demonstrate that the programmable-velocity intensity peak of a spatiotemporally structured, two-color laser pulse can be used to control the emission angle, focal spot, and spectrum of the THz radiation. Of particular interest for applications, a structured pulse with a subluminal intensity peak can drive highly focusable, on-axis THz radiation.