Superlensing plano-convex-microsphere (PCM) lens for direct laser nano-marking and beyond

A high-performance all-dielectric lens, formed by integrating a conventional plano-convex lens with a high-index microsphere lens (PCM), was developed for far-field super-resolution applications. The PCM lens features a theoretical resolution of $\sim\lambda /{2.5}$∼λ/2.5 in air with a WD $\sim 2\;{\unicode{x00B5} \rm m}$∼2µm away from the lens. When combined with a femtosecond laser, the actual patterning resolution can reach $\sim\lambda /{3.5}$∼λ/3.5. The unusual focusing properties were theoretically and experimentally verified, and direct laser nano-writing of arbitrary patterns and nanostructures on various substrates was demonstrated. This Letter can be naturally extended to other super-resolution applications, including imaging, sensing, and trapping, with the potential of developing next-generation low-cost direct laser nano-marking machine and super-resolution imaging nanoscope.