A solar concentrator is composed of the cascading of the first light guiding module and a second light guiding module. The solar light is collected and guided simultaneously toward the light propagation destination by the light guiding modules. By cascading the light guiding modules in the direction of guiding, the solar concentrator has thinner thickness than the traditional concentrator and has a zero back focal distance to reduce the assembly cost. The solar concentrator utilizes the optical design concept of coincident image points from both the relay and converging optics such that the optical flux is increased in the cascading light guiding modules while the light propagation direction within the concentrator is maintained.