Multiple-Wavelength Achromatic Superresolution Focusing with Optimized Constructive Interference

Recently, there has been growing interest in developing superresolution lenses to focus light beyond the conventional diffraction limit in the far field. Achromatic superresolution is particularly attractive for many practical applications. However, it remains a great challenge to realize an achromatic superresolu-tion focusing lens with both a high numerical aperture and a small depth of focus, which is critical for superresolution imaging with high longitudinal resolution. Here, a method for preparing a multiwave-length achromatic superresolution lens with a high numerical aperture is proposed to control the wave front through a binary-phase zone plate for generating a transverse superresolution focal spot with a small depth of focus. The approach is experimentally verified with an achromatic superresolution lens with a high numerical aperture of 0.95 at six wavelengths in the visible range between 405 and 684 nm. The proposed method is practical for superresolution-related applications, including imaging, microscopy, and data storage.