Superoscillation: from physics to optical applications

The resolution of conventional optical elements and systems has long been perceived to satisfy the classic Rayleigh criterion. Paramount efforts have been made to develop different types of superresolution techniques to achieve optical resolution down to several nanometres, such as by using evanescent waves, fluorescence labelling, and postprocessing. Superresolution imaging techniques, which are noncontact, far field and label free, are highly desirable but challenging to implement. The concept of superoscillation offers an alternative route to optical superresolution and enables the engineering of focal spots and point-spread functions of arbitrarily small size without theoretical limitations. This paper reviews recent developments in optical superoscillation technologies, design approaches, methods of characterizing superoscillatory optical fields, and applications in noncontact, far-field and label-free superresolution microscopy. This work may promote the wider adoption and application of optical superresolution across different wave types and application domains. Using superoscillations in light for superresolution imagery Researchers are getting closer to achieving ‘superresolution’ images by employing localized high-amplitude oscillations in light waves. Cheng-Wei Qiu of the National University of Singapore and colleagues in China reviewed developments in optical ‘superoscillation’ technologies, which aim to overcome current limitations in superresolution techniques requiring contact with the observed object, the use of fluorescent labels, or viewing that is restricted to the near-field of a lens. Superoscillation is a mathematical phenomenon in which a light wave contains local frequencies that are large in amplitude. Optical systems employing this phenomenon could improve the ability to distinguish two tiny objects separated by nanoscale-length distances. Recent developments show potential for applications in telescopes, microscopy, and ultrahigh density optical data storage. Improving the design of superoscillatory lenses could overcome challenges in efficiently focusing more of the incident optical energy.