LIGHT RAY CONCENTRATOR

An optical device and systems using an optical device are provided, where the optical device may be configured for collimating incoming light rays. The optical device may include a host medium substantially comprised of a transparent material and an array of substantially transparent structures embedded within the host medium. The structures of the array each include a convex side presented to the incoming light rays and a concave side that passes light rays through toward the output face of the host medium, collimating the rays. Multiple stages of arrays may be provided in the optical device, typically with lengthening aspect ratios and increasing indexes of refraction in a direction from the input face toward the output face. The systems may use the optical device for using an exterior light to illuminate an interior space in a building or to generate power.