Faceted concentrators optimized for homogeneous radiation

For technical reasons, large three-dimensional compound parabolic concentra tors (CPC's) are often built from facets with either no or only one-dimensi onal curvature. We analyze CPC approximations made with various numbers of axial and circumferential subdivisions, incident radiation within half-angl es of 10 degrees and 30 degrees is considered, The reflectivity of the mirr ors is assumed to be 90% or 95%. The performance of faceted concentrators c an be significantly improved by optimization as compared with heuristic CPC approaches. The highest increase in transmission that we observed was 19% greater as compared with that of a heuristic CPC approximation. The shapes of the optimized concentrators differ from that of a classic CPC, and most of the optimized concentrators are longer than a classic CPC. For practical concentrators with a small number of facets, the optimized geometry provid es better performance than a heuristic approximation of the CPC shape. (C) 2000 Optical Society of America.