Advances in Dielectric Microspherical Lens Nanoscopy: Label-Free Superresolution Imaging

The optical diffraction limit, also known as Abbe's limit, has long been a barrier for the development of advanced optical microscopy, thus hampering attempts to explore subdiffraction-scale entities with light. Dielectric microobjects, such as microfibers and microspheres, display unique optical properties including photonic nanojet (PNJ) effects, optical whispering-gallery resonances, and optical directional antenna effects, which are benefits for nanoscale optical engineering applications, such as nanoimaging, nanopatterning, and nanodetection. Dielectric microspherical lens nanoscopy (DMN) has been widely studied for optical superresolution imaging because of its ability of label-free noninvasive nanoscale investigation. In this review article, we present the principles of DMN and recent advances in studies of imaging mechanism and imaging modes. An overview of DMN imaging applications in label-free superresolution imaging is summarized as well. Furthermore, other DMN applications, including microsphere-assisted laser nanopatterning and nonlinear optical effects enhancements, are also discussed.