Visible Light Communications via Intelligent Reflecting Surfaces: Metasurfaces vs Mirror Arrays

We propose two types of intelligent reflecting systems based on programmable metasurfaces and mirrors to focus the incident optical power towards a visible light communication receiver. We derive the required phase gradients for the metasurface array reflector and the required orientations of each mirror in the mirrors array reflector to achieve power focusing. Based on which, we derive the irradiance expressions for the two systems in the detector plane to characterize their performance in terms of aiming and focusing capabilities. We show analytically that the number of reflecting elements along with the relative source - reflector dimensions determine the system power focusing capability. Moreover, we quantify analytically the received power gain compared with reflector-free systems. In addition, we introduce a new simple metric to assess the relative reflectors' performance for a given source, detector, reflector layout. Finally, we verify the analytical findings regarding absolute and relative reflectors' performance via numerical simulations.