Harvesting Planck radiation for free-space optical communications in the LWIR band

We demonstrate a free-space optical communication link with an optical transmitter that harvests naturally occurring Planck radiation from a warm body and modulates the emitted intensity. The transmitter exploits an electro-thermo-optic effect in a multilayer graphene device that electrically controls the surface emissivity of the device resulting in control of the intensity of the emitted Planck radiation. We design and demonstrate multiple amplitude-modulated optical communication schemes and provide a link budget for communications data rate and range based on our experimental electro-optic characterization of the transmitter. We present an experimental demonstration achieving error-free communications at one hundred bits per second over laboratory scales and discuss how to scale this to >25km links. Finally, we discuss how to apply this system to achieve steganographic communications. https://arxiv.org/abs/2210.06942