Geometry and performance comparison of three optical concentrators for optical wireless communication applications

This study presents a comparative analysis of the geometries and optical performance of three non-imaging concentrators for optical wireless communication receivers, including the compound parabolic concentrator (CPC), the dielectric totally internally reflecting concentrator (DTIRC), and a novel freeform concentrator. All designs use a 1.5mm diameter detector, identical exit apertures, the same acceptance half-angle, and polymethyl methacrylate (PMMA) as the material. The CPC employs symmetric parabolic profiles (hollow or dielectric-filled), while the DTIRC utilizes a curved entrance surface and total internal reflection along its sidewalls. The proposed freeform concentrator is specifically optimized to achieve highly uniform irradiance distribution on the detector, overcoming the non-uniform illumination inherent in conventional CPC and DTIRC designs. Ray-tracing simulations demonstrate that the freeform concentrator provides more than 10% higher optical gain compared to the CPC and DTIRC, while maintaining irradiance uniformity exceeding 90%. At a 6^◦ acceptance angle, its height is 5.97 times smaller than that of the CPC and 1.42 times smaller than that of the DTIRC. These results indicate that the freeform design offers a compelling combination of higher efficiency, better uniformity, and significantly more compact size for high-speed optical wireless receivers.