Mid-infrared supercontinuum laser source with efficient spectral enhancement in 3.7 µm.

A 3-5 µm mid-infrared (MIR) laser has a wide range of applications in biological tissue ablation, remote spectral fingerprint recognition, and directional infrared countermeasures. However, the performance of conventional MIR lasers has long been hindered by restricted wavelength radiation, spectral power efficiency, and system stability. Here, a highly efficient, compact, and stable MIR light source is reported, which is directly generated from a supercontinuum (SC) laser with a long wavelength edge of 4.2 µm in a 7 µm core diameter fluorotellurite fiber. Based on the integration of a high-peak-power pump light source and a small-core-diameter nonlinear medium, efficient nonlinear frequency conversion from traditional near-infrared laser to mid-infrared laser has been achieved, resulting in a significantly enhanced MIR spectrum of 3.7 µm, exceeding the pump peak of 2 µm by more than 12 dB. The pump conversion efficiency is 50.8%, with 94.3% of the spectral power distributed above 2.4 µm and 71.4% above 3 µm. This study has opened up a feasible avenue for obtaining high-efficiency mid-infrared band lasers that meet practical application needs.