Design of a gradient-index lens with a compound parabolic concentrator shape as a visible light communication receiving antenna.

We propose a design for a gradient lens that can extend the field of view and receive higher optical power for indoor visible light communication systems. The proposed structure is an axially symmetric lens with a refractive index gradient distribution in the axial direction and a slight gradient in the radial direction, and with a spherical top surface and side surface in a compound parabolic concentrator (CPC) shape. The radius of the outlet of the CPC is 3 mm, and the inlet radius is 6.8 mm with a 9.04 mm radius of curvature. The height of the receiving system is 15.2 mm, resulting in the small volume of the structure. Simulation results show that the half field of view (FOV) of the lens can reach 36.2°, while the gain is higher than that of a bare CPC. The designed receiving system has an average receiving gain ∼1.72 times larger than a bare CPC-based system, and is suitable for indoor visible light communication.