Multi-Gb/s free-space communication with energy-efficient room-temperature quantum cascade laser emitting at $8. 1\ \mu \mathrm{m}$

We demonstrate a free-space transmission with a direct electrical modulation in a quantum cascade laser emitting in one of the transparency windows of the atmosphere, near
$8.1\ \mu \mathrm{m}$
. The advantages of the presented work are a room-temperature setup, real-time high-speed operation and low-power consumption.