High‐Numerical‐Aperture Dielectric Metalens for Super‐Resolution Focusing of Oblique Incident Light

Recently, developments in superoscillatory optical devices have allowed for label‐free far‐field optical super‐resolution technology by allowing engineering of optical point‐spread functions beyond the traditional Abbe diffraction limit. However, such superoscillatory optical devices are optimized for the normal‐incident operation, which inevitably leads to a comparatively slow imaging acquisition rate in the application of super‐resolution microscopy. Here, a super‐resolution metalens is demonstrated with a high numerical aperture that can focus oblique incident light into a hot spot with a size smaller than the diffraction limit at the visible wavelength. This super‐resolution metalens has a numerical aperture of as large as 0.97, a focal length of 38.0 µm, a radius of 151.9 µm, and a field of view of 4° that enables super‐resolution focusing on the focal plane at a wavelength of λ = 632.8 nm. In a 5.6λ × 5.6λ field of view on the focal plane, the size of the focal spot is smaller than 0.45λ, which is only 0.874 times the corresponding Abbe diffraction limit. The super‐resolution metalens offers a promising way toward fast‐scanning label‐free far‐field super‐resolution microscopy. Due to their promising potentials in super‐resolution imaging, super‐resolution metalenses are widely investigated. However, previously reported super‐resolution metalenses only work for normal incident waves, which greatly restricts their practical applications. Here, a super‐resolution metalens is reported with a high numerical aperture of 0.97 and a field of view of 4°, which offers a promising way toward fast‐scanning label‐free far‐field super‐resolution microscopy.