Free-Space Optical Communications using Terahertz Lasers at Gbit/s Data Rates

High-speed free-space optical (FSO) communication in the terahertz (THz) spectrum is gaining attention as a solution to the rising demand for wireless data. THz frequencies (0.1-10 THz) offer ample bandwidth and can deliver fiber-equivalent data rates wirelessly, making them suitable for beyond-5G backhaul [1]. Terahertz quantum cascade lasers (THz QCLs) offer multi-gigabit modulation speed in FSO links. The THz FSO communication systems >1 THz remain largely unexplored due to limitations in source and photodetector limitations. However, significant progress in sources, modulators, and receivers has improved output power, bandwidth, and sensitivity. [2]. A THz QCL link at 20 Mbit/s was demonstrated [3], and a recent link achieved 1 Mbit/s with a room-temperature graphene receiver [4]. However, achieving higher data rates in a THz FSO communication link remains a significant goal.