The „field resolved infrared science“ group has demonstrated for the first time the generation of octave-spanning mid-infrared using a BGSe nonlinear crystal. A Cr:ZnS laser system delivering 28-fs pulses at a central wavelength of 2.4 µm is used as the pump source, which drives the intra-pulse difference frequency generation inside the crystal. As a result, a coherent broadband mid-infrared continuum spanning from 6 to 18 µm has been obtained. It shows that the BGSe crystal is a promising material for broadband, few-cycle mid-infrared generation via frequency down conversion with femtosecond pump sources.
J. Zhang, Q. Wang, J. Hao, H. Liu, J. Yao, Z. Li, J. Liu, K. Mak
"Broadband, few-cycle mid-infrared continuum based on the intra-pulse difference frequency generation with BGSe crystals"
Optics Express 28, 37903 (2020)