Milliwatt average power, MHz-repetition rate, broadband THz generation in organic crystal BNA with diamond substrate

TL;DR

This paper reports a high-power, broadband THz source using organic crystal BNA with diamond cooling, achieving the highest average power to date and demonstrating its potential for advanced spectroscopy applications.

Contribution

It introduces a high-repetition-rate, high-average-power THz generation method using BNA crystal with diamond cooling, surpassing previous power levels and exploring thermal limitations.

Findings

Maximum THz power of 0.95 mW at 13.3 MHz

Spectral bandwidth up to 6 THz at -50 dB

Thermal effects limit power scaling in BNA

Abstract

We demonstrate a 13.3 MHz repetition rate, broadband THz source with milliwatt-average power, obtained by collinear optical rectification of a high-power Yb-doped thin-disk laser in the organic crystal BNA (N-benzyl-2-methyl-4-nitroaniline). Our source reaches a maximum THz average power of 0.95 mW with an optical-to-THz efficiency of 4e-4 and a spectral bandwidth spanning up to 6 THz at -50 dB, driven by 2.4 W average power (after an optical chopper with duty cycle of 10%), 85 fs-pulses. This high average power excitation was possible without damaging the crystal by using a diamond-heatsinked crystal with significantly improved thermal properties. To the best of our knowledge, this result represents the highest THz average power reported so far using the commercially available organic crystal BNA, showing the potential of these crystals for high average power, high repetition rate femtosecond excitation. The combination of high power, high dynamic range, high repetition rate and broadband spectrum makes the demonstrated THz source highly attractive to improve various time-domain spectroscopy applications. Furthermore, we present a first exploration of the thermal behavior of BNA in this excitation regime, showing that thermal effects are the main limitation in average power scaling in these crystals.