Chromatic Effect for THz Generation in a Novel Wave-front Tilt Scheme

TL;DR

This paper introduces a novel lithium niobate crystal design and reveals the significant impact of laser pulse chirp on enhancing terahertz generation efficiency in wave-front tilt schemes.

Contribution

A new dual-face-cut lithium niobate crystal with Brewster coupling was developed, and the role of laser pulse chirp in improving THz generation efficiency was systematically investigated.

Findings

Predicted THz conversion efficiency of 10% at 0.5cm-1 absorption.

Discovered laser pulse chirp greatly enhances THz generation.

Optimized multi-parameter scheme for higher efficiency.

Abstract

Deriving single or few cycle terahertz pulse (THz) by intense femtosecond laser through cascaded optical rectification in electro-optic crystals is a crucial technique in cutting-edge time-resolved spectroscopy to characterize micro-scale structures and ultrafast dynamics. In the past decade, lithium niobate (LN) crystal implementation of wave-front tilt scheme has been prevalently used, while painstaking efforts have been invested in order to achieve higher THz conversion efficiency. In this research we developed a brand new type of LN crystal possessing dual-face-cut and Brewster coupling, and conducted experimental and simulative investigation systematically to optimize the multi-dimensionally entangled parameters in THz generation, predicting the extreme conversion efficiency of 10% is potentially promising at the THz absorption coefficient of 0.5cm-1. More remarkably, we first discovered that the chirp of the driving laser pulse plays a decisive role in the wave-front tilt scheme, and the THz generation efficiency could be enhanced tremendously by applying an appropriate chirp.