Multilayer dielectric reflective metalens without metallic mirror

While transmission-mode metalenses have been extensively studied, reflection-mode metalenses remains almost unexplored, presenting advantages in terms of improved efficiency and reduced complexity. In this work we investigate a multilayer dielectric metalens operating in reflection mode without a metallic layer. Simulations and analysis demonstrate the performance of the metalens, with an 84% reflectivity the metalens proves its efficacy in reflection mode. At a numerical aperture of 0.15, the metalens achieves 33% focusing efficiency, facilitating efficient light manipulation and subwavelength resolution. Additionally, the metalens exhibits a well-defined focal spot with a full width at half maximum of 2.03 μm, approaching the diffraction limit.