Enabling High-Power, Broadband THz Generation with 800-nm Pump Wavelength

TL;DR

This paper demonstrates that bonding BNA crystals to sapphire significantly enhances their damage threshold, enabling high-field, broadband THz generation with 800-nm pump light, surpassing previous limitations.

Contribution

The study introduces a novel bonding technique to improve BNA's damage threshold, allowing higher electric fields and broader THz spectra with 800-nm pumping.

Findings

Bonded BNA (BNA-sapphire) produces 2.5 times higher electric fields than bare BNA.

Peak-to-peak electric fields exceeding 1 MV/cm achieved with BNA-sapphire.

Broadband THz components from 0.5 to 5 THz generated with high fields.

Abstract

The organic terahertz (THz) generation crystal BNA has recently gained traction as a valuable source to produce broadband THz pulses. Even when pumped with 800-nm light, thin BNA crystals can produce relatively high electric fields with frequency components out to 5 THz. However, the THz output when pumped with 800-nm light is limited by the damage threshold of the organic crystal. Here we report that the damage threshold of BNA can be significantly improved by physically bonding BNA to a high-thermal conductivity sapphire window. When pumped with 800-nm light from an amplified Ti:sapphire laser system, our bonded BNA (BNA-sapphire) generates 2.5 times higher electric field strengths compared to bare BNA crystals. We characterize the average damage threshold for bare BNA and BNA-sapphire, measure peak-to-peak electric field strengths and THz waveforms, and determine the nonlinear transmission in BNA. Pumping BNA-sapphire with 800-nm light results in peak-to-peak electric fields exceeding 1 MV/cm, with strong broadband frequency components from 0.5-5 THz. Our BNA-sapphire THz source is a promising alternative to tilted pulse front LiNbO3 THz sources, which will enable many research groups without optical parametric amplifiers to perform high-field, broadband THz spectroscopy.