Optical super-resolution by high-index liquid-immersed microspheres

It is experimentally shown that barium titanate glass microspheres with diameters (D) in the range 2–220 μm and with high refractive index (n ∼ 1.9–2.1) can be used for super-resolution imaging of liquid-immersed nanostructures. Using micron-scale microspheres, we demonstrate an ability to discern the shape of a pattern with a minimum feature size of ∼λ/7, where λ is the illumination wavelength. For spheres with D > 50 μm, the discernible feature sizes were found to increase to ∼λ/4. Detailed data on the resolution, magnification, and field-of-view are presented. This imaging technique can be used in biomedical microscopy, microfluidics, and nanophotonics applications.