High-efficiency narrowband terahertz generation in novel wide-bandgap barium chalcogenide crystals

TL;DR

This paper explores novel barium chalcogenide crystals for efficient narrowband terahertz generation, demonstrating high conversion efficiency and potential for imaging and spectroscopy applications.

Contribution

It introduces new barium chalcogenide crystals with high optical damage thresholds for narrowband THz generation via optical rectification.

Findings

Achieved up to 0.8×10^(-5) optical-to-THz conversion efficiency.

Generated narrowband THz pulses at 1.9 to 2.5 THz with 3-4% bandwidth.

Demonstrated suitability for security and medical imaging applications.

Abstract

We report on extensive experimental investigation of novel barium chalcogenides (BaGa4Se7, BaGa2GeSe6 and BaGa2GeS6) for generation of a strong narrowband terahertz (THz) radiation. The Ba-containing compounds demonstrate the large bandgap values, high optical damage threshold and wide transparency range from the visible to mid-infrared region, coupled with narrowband transparency windows in the THz frequency range. In these windows a THz generation via the second-order nonlinear process of optical rectification occurs under optical pumping by a 50-GW high-power Cr:forsterite laser leading to intrinsically narrowband THz pulses. The highest optical-to-THz conversion efficiency of 0.8^10(-5) is reached in the Z-cut BaGa2GeS6 crystal in the saturation regime and corresponds to an output energy of 20 nJ. Ba compounds provide narrow-bandwidth THz pulses at the frequencies in the range from 1.9 to 2.5 THz with a relative bandwidth of 3-4%, necessary for imaging and spectroscopy for security or medical applications.