Unusual Superressolution Properties of Dielectric Microspheres
Pin-Yi Li1,2*, Yang Tsao1,3, Shi-Wei Chu3, Chih-Wei Chang1
1Center for Condensed Matter Science, National Taiwan University, Taipei, Taiwan
2Graduate Institute of Applied Physics, National Taiwan University, Taipei, Taiwan
3Department of Physics, National Taiwan University, Taipei, Taiwan
* presenting author:Pin-Yi Li, email:b01202041@ntu.edu.tw
Superresolution techniques are widely-used approaches to overcome diffraction limit. However, these techniques encounter a lot of difficulties, such as sluggish scanning speeds, limited lifetime of fluorescent dyes, or sophisticated fabrication processes. Recently, it has been shown that dielectric microspheres can bring the sub-wavelength information to far-field, achieving superresolution by a white-light source. We find that a semi-immersed geometry by coating the microspheres with PMMA can greatly improve the resolution, reaching the best spatial resolution up to λ/7.5. Notably, the best resolution results are all from metallic samples.
The reason why the microspheres can achieve superresolution is still under debate. We have also conducted two different experiments to eliminate the mechanisms suggested by earlier works. That is, neither photonic nanojets nor evanescent waves are responsible for the superresolution. In fact, our simulations show that the microspheres are like ordinary solid immersion lenses with a diameter-dependent focal width.

Keywords: Microspheres, Superresolution