RETRACTED ARTICLE: Modelling and verification of white light oil immersion microsphere optical nanoscope
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Modelling and verification of white light oil immersion microsphere optical nanoscope Jinzhong Ling1 • Xiaorui Wang1 • Dancui Li1 • Xin Liu1
Received: 28 September 2017 / Accepted: 20 October 2017 Springer Science+Business Media, LLC 2017
Abstract Microsphere has been demonstrated for imaging resolution improvement based on optical microscope, and applied in many engineering and biological fields successfully, while its mechanism is still inconclusive due to the complex physics of both near-field and far-field optics involved. In this paper, a comprehensive simulation model based on point spread function is built to develop a physical insight into microsphere optical nanoscope by numerical simulation. With this model, the Fresnel-region focusing of microsphere lens is studied, which shows the contradiction between focal spot size and focal length. Furthermore, the gap between microsphere and the sample surface is investigated by numerical simulation and experimental verification. As increasing of this gap, the image resolution declines rapidly, and the image becomes blur more and more. At last, a customized sample with a flower pattern etched on silicon substrate is demonstrated with microsphere optical nanoscope, and its feature sizes of 51 nm line width are imaged clearly. While it is generally accepted that microsphere optical nanoscope can be implemented in nano-imaging, these findings quantified the limit on image resolution of this setup, which serves as a general guideline in system design of the other microsphere or micro-particle assisted microscope/nanoscope. Keywords Imaging systems Microscope Microsphere Super-resolution
1 Introduction Optical microscope is one of the most powerful tools for us to observe the micro-world in scientific research, industrial inspection, medical diagnosis, and even daily life. However, its resolution is limited by the diffraction limit and determined by the incident wavelength & Xiaorui Wang [email protected] 1
School of Physics and Optoelectronic Engineering, Xidian University, Xi’an 710071, Shaanxi, China
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and numerical aperture (NA) of optical lens. To overcome the diffraction limit and attain super-resolution images by optical microscope, many techniques have been inspired or proposed, such as near-field scanning optical microscope (NSOM) (Neuman et al. 2015; Hossain et al. 2014; Gong et al. 2017), super-oscillatory lenses (SOL) (Rogers et al. 2015; Qin et al. 2015), stimulated emission depletion microscope (STED) (Willig et al. 2006), plasmonic lens (Liu et al. 2005), and perfect lens with negative index metamaterials (Zhang and Liu 2008; Lu and Liu 2012). These techniques mentioned above, however, either need long imaging time due to point by point scanning or need sophisticated engineering design and highly accurate fabrication due to the complexity of the imaging system, which limits their practical applications. Recently, a novel approach, microsphere optical nanoscope, was demonstrated in 2011 (Wang et al
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