Metalenses for subwavelength imaging

Devices that form an optical image with a subwavelength resolution in real time—metalenses—are considered. Such devices either operate with near optical fields or convert near fields into wave fields. As a result, the spatial resolution of these devices is not limited by the diffraction limit. At the same time, the image is formed at a considerable distance from the object, which distinguishes near-field metalenses from the instruments used in near-field probe microscopy. Metalenses are implemented based on metamaterials or their two-dimensional analogs, metasurfaces. Historically, this line of research was based on the so-called perfect lens, the concept of which did not withstand experimental verification but gave impetus to the development of real metalenses. Depending on the device and principle of operation, metalenses are called either superlenses or hyperlenses.