Abstract: An optical energy gathering device having a large annular area provides advantages over a lens having equal collection area. Coupled with advantages afforded by keeping the device geometry in a planar form, the optical energy concentrator/retroreflector allows a deployment freedom not usually associated with lensing systems. The energy concentrator includes a transparent sheet, a director disposed in the perimetral region of the sheet for directing electromagnetic energy incident on the perimetral region to a concentrating region of the sheet, and a router disposed at the concentrating region for routing the directed electromagnetic energy out of the sheet. The thickness of the sheet may be substantially less than the mean distance from the concentrating region of the sheet to the perimetral region, and the area of the sheet's perimetral region may be substantially less than the total area of the sheet.