Free-space communication and remote sensing using mid-infrared quantum cascade lasers down to few-photon light level

The implementation of free-space optical communication and sensing systems at mid-IR wavelengths represents a critical advancement for next-generation high-speed communication networks, offering a robust solution for environments where traditional radio frequency (RF) and near-IR systems face significant limitations. Here we report on our recent advancements in free-space optical communication and sensing using mid-IR quantum cascade lasers (QCLs). Two setups are discussed, one using a QCL comb for optical communication in the 4-μm atmospheric transparency window and one LIDAR based on single-mode cw QCL for range finding and air quality analysis. Experimental results demonstrating few-photon coherent detection will be shown.