Tunable narrowband THz generation in the organic crystal BNA

TL;DR

This paper demonstrates a method for generating tunable narrowband terahertz pulses using a specific organic crystal, BNA, with improved stability and a broad tunable frequency range, simplifying the setup by avoiding additional amplification stages.

Contribution

It introduces a collinear phase-matched difference-frequency generation technique in BNA for THz generation, eliminating the need for optical parametric amplifiers and enhancing stability.

Findings

Tunable THz pulses from 0.25 to 2.1 THz achieved.

Chirped-pulse excitation suppresses multiphoton absorption.

Stable, narrowband THz generation in BNA demonstrated.

Abstract

The generation of tunable narrowband pulses is increasingly being pursued in terahertz science, for example to study the nonlinear response of individual modes of solids and molecules. Here, we extend the chirp-and-delay method to achieve collinear phase-matched difference-frequency generation in the organic crystal N-benzyl-2-methyl-4-nitroaniline (BNA-S), which results in tunable narrowband terahertz pulses. In this configuration, the fundamental frequency of a Ti:sapphire amplifier is used - eliminating the need for optical parametric amplifiers typically required for THz generation in other organic crystals. Chirped-pulse excitation suppresses multiphoton absorption in BNA, improving stability and extending crystal lifetime. The source delivers THz transients tunable from 0.25 THz to 2.1 THz with adjustable spectral width.