Abstract: A solar concentrator assembly comprises a stepped wave-guide assembly, a reflective mirror assembly, and an optical target providing unit. The stepped wave-guide assembly includes at least one surface, comprising a set of parallel but offset adjacent surfaces, and an opposing surface. The wave-guide assembly propagates light in a total internal reflection mode between the at least one surface and the opposing surface. The wave-guide assembly also includes transition surfaces between the adjacent parallel surfaces and the transition surfaces include edges perpendicular to a longitudinal axis of the wave-guide assembly. The reflective mirror assembly includes a plurality of mirrors each being aligned to reflect the light to one of the transition surfaces between two of the parallel adjacent surfaces. The optical target providing unit converts solar energy from the light propagated in the wave-guide assembly to a different form of energy.