Enhancing plasmonic structured illumination microscopy with surface plasmon coupled emission.

Plasmonic structured illumination microscopy (PSIM) is a super-resolution technique that utilizes surface plasmon polaritons (SPPs) with higher frequency as the structured light; thus, it is able to break the diffraction limit with a 3-4 times resolution enhancement. However, the low efficiency of near-field fluorescence collection results in a low imaging signal-to-noise ratio (SNR) of PSIM. In this paper, we propose a method to enhance the performance of PSIM with surface plasmon coupled emission (SPCE). Compared to conventional fluorescence detection, it achieves a 5-fold enhancement in fluorescence collection efficiency by collecting SPCE signals, which facilitates better collection of near-field information of targets. In our PSIM, samples with different fluorescence excitation wavelengths are distinguished by adjusting the collection angle, since SPCE has high wavelength sensitivity. Especially, the technique of fluorescence emission difference (FED) for SPCE was used to obtain a 5.7-fold resolution enhancement, which further enhanced the super-resolution capability of PSIM. This method improves the SNR and resolution of PSIM and facilitates more detailed observation of biological cells.