Fluorescence emission difference microscopy by superoscillation excitation.

A superresolution fluorescence emission difference (FED) microscopy based on superoscillation excitation is investigated. The solid superoscillation excitation spot is produced by the radially polarised Laguerre-Gaussian beam (LG), and the donut superoscillation excitation spot is produced by the same LG beam with spiral phase modulation. We show that the superoscillation excitation can enhance the spatial resolution of FED microscopy. When the ratio of the pupil radius and the second moment radius of the LG3,1 beam is 0.85 and the subtractive factor is 0.3, the resolution can be enhanced about 2 times than the general confocal microscopy. Compared with the general FED microscopy, the resolution can be enhanced about 1.1 times. Our simulations also demonstrate that two-view Richardson-Lucy (RL) deconvolution method can reduce the effect of side lobes, which is related to subtractive factor and pinhole. LAY DESCRIPTION: The fluorescence emission difference (FED) microscopy is a high-resolution light microscopy, which is based on the subtraction of images produced by two different confocal imaging modes. Here, the solid excitation spot is used in one imaging mode, and the donut excitation spot is in another imaging mode. There are various ways that the solid and donut excitation spots can be structured, but superoscillation excitation spots are still not used in the FED microscopy. Considering that the main lobe of superoscillation can be arbitrarily small in principle, we exploit the radially polarised Laguerre-Gaussian beam (LG) and spiral phase plate to produce superoscillation solid and donut spots. We present a detailed analysis about the performance of FED microscopy via superoscillation excitation. Our analysis is based on vector diffraction theory and supported by simulations of imaging. We find the proposed FED microscopy has better resolution than the confocal microscopy or the general FED microscopy excited by Gaussian beam. Especially, two-view Richardson-Lucy (RL) deconvolution method can reduce the negative impact of strong side lobes, which is related to the subtractive factor and the size of pinhole located at the detector.