Compact beam expander based on planar structure to avoid inner focus

Based on the planar optical theory, compact beam expanders are proposed to miniaturize the dimension of an optical system. Both simulated and experimental results have demonstrated the designate functions of the proposed beam expanders. Such planar beam expanders (PBEs) consist of both parabolic mirrors which locate on the both sides of one substrate. The calculated results have showed that those PBEs, possessing thinner volume compared with the conventional beam expanders, are achromatic and aberration-free. To verify the optical performance of the designed PBEs, two of them were individually fabricated using the diamond grinding technique. The measured results have shown that the designate functions of the fabricated PBE have been achieved.