Accurate experimental detection method for characterizing superoscillatory lenses made from multiannular metasurfaces

To verify the superoscillatory optical diffraction focusing characteristics of multiannular metasurfaces (MAMs), we propose an experimental detection method. It consists of two parts, the reflection positioning optical system and transmission detection imaging system. The best focal plane of the superoscillatory optical diffraction focus for the MAM can be precisely positioned through the reflection positioning optical system, which is the core part of the experimental detection method and is based on the structured illumination optical sectioning principle. A typical MAM is designed using vectorial angular spectrum (VAS) theory and a genetic algorithm. It was fabricated by focused ion-beam milling. The three-dimensional finite-difference time-domain method is used to verify the intensity distribution of the focus predicted by the VAS theory. For the designed 14-μm-diameter MAM at a wavelength of 640 nm, the simulation result broadly agrees with the experimental result obtained from the transmission microscopic imaging system. The proposed detection method can be used in fields such as optical diffraction focusing and subwavelength resolution imaging.