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 a 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.