Full-chain simulation on microsphere assisted nanoscopy for its super-resolution imaging characteristics

Microsphere-assisted nanoscopy has attracted much attention for its advantages of high resolution, label-free and simple setup. In this article, a full-chain simulation model of the microsphere lens imaging was developed, where both the effects of interaction between light and nano-structures in near-field and the light propagation from near-field to far-field are considered. Upon simulation, we studied two key factors that affect the imaging resolution and imaging quality of microsphere lens: immersion condition and the defocus amount. The former affects imaging contrast and can be used for the resolution improvement, while the latter affects the imaging quality. Then, we confirmed the above simulation conclusion experimentally. In addition, in order to accurately measure the gap between the microspheres and the sample, we proposed a distance monitoring scheme that uses Newton's rings to feedback the gap changing. Comparing with previous simulation models considering only focusing effect, our simulation model of the microsphere lens is more accurate, since more fundamental physical models are involved. Moreover, our simulation method demonstrates the imaging result directly, which truly reflects what you see is what you get. This work can help us better understand the super- resolution mechanism of the microsphere lens, and help us design and optimize the microsphere lens etched with micro/nano-structures for light field modulation.