Design of three-dimensional nonimaging concentrators with inhomogeneous media

A three-dimensional nonimaging concentrator is an optical system that transforms a given four-parametric manifold of rays reaching a surface (entry aperture) into another four-parametric manifold of rays reaching the receiver. A procedure of design of such concentrators is developed. In general, the concentrators use mirrors and inhomogeneous media (i.e., gradient-index media). Using this method, we obtain an axisymmetrical concentrator with flat-entry aperture and receiver, which collects every ray that forms, at the entry aperture, an angle lower than a given value with the normal to this surface. The concentrator has the maximum concentration allowed by the theorem of conservation of phase-space volume. This is the first known concentrator with such properties. The Welford-Winston edge-ray principle in 3-D geometry is proven under several assumptions. The linear compound parabolic concentrator is derived as a particular case of the procedure of design.