
{"publication_number": "US-2012028007-A1", "abstract": "an electromagnetic black hole may be fabricated as concentric shells having a permittivity whose variation is at least as great as an inverse square dependence on the radius of the structure . such a structure concentrates electromagnetic energy incident thereon over a broad range of angles to an operational region near the center of curvature of the structure . devices or materials may be placed in the operational region so as to convert the electromagnetic energy to electrical signals or to heat . applications included solar energy harvesting and heat signature detectors .", "application_number": "US-201113190904-A", "description": "exemplary embodiments may be better understood with reference to the drawings , but these embodiments are not intended to be of a limiting nature . to achieve substantially equal performance at any incidence angle direction , a spherically symmetric shell , for example , may be used , as shown in fig1 a . the shell 5 may have an outer radius r s , 6 , and an inner radius r c , 7 , with the radial variation in the shell permittivity \u2208( r ) matching those of the outer medium 9 and of the internal core 10 at the corresponding interfaces where the core radius r c = r \u221a{ square root over (\u2208 0 /\u2208 c )