LAUSR

Abstract A novel scheme to achieve a back reflector based on two-dimensional dielectric-metal graded metasurface is proposed, which presents high-efficiency over a broad range of incident solid angles and wavelengths. The remarkable performance of the back reflector is achieved by an effective optimization by searching the maximum reflection and the lowest deviation angle of solid space at a certain diffraction order. As a result, the optimized structure, working as a two-dimensional Littrow grating, is able to funnel the incident energy into the diffraction order (1,1) to reflect almost all (> 92%) the impinging light back to the source based on Huygens-Fresnel principle. The working wavelength of the back reflector can be tuned by simply adjusting the structural parameters of the graded metasurface.