Over 8 times resolution enhancement via structured illumination microscopy mediated by tunable bulk plasmon polaritons

Enhancing imaging resolution is a crucial point in structured illumination microscopy (SIM). However, the high-frequency structured light fields required for super-resolution imaging are prone to introducing frequency gaps during the process, leading to reconstruction artifacts. Simultaneously achieving high-resolution imaging and minimizing reconstruction artifacts in SIM remains a critical challenge. In this manuscript, we overcome this challenge by introducing a method that generates a tunable structured light field with high spatial frequencies. The optical field is the bulk plasmon polaritons (BPPs) generated by an integrated structure comprising a metal grating, a hyperbolic metamaterial (HMM), and a reverse Kretschmann (RK) configuration. Its spatial frequency can be tuned by adjusting the thickness of the nanocavity between the RK configuration and the HMM, enabling the extraction of sample frequency information across an exceptionally wide and continuous range, thereby suppressing artifacts arising from missing frequency information. The BPPs exhibit a maximum spatial frequency reaching up to 6.6 times that of the incident light. Therefore, the tunable BPPs based SIM (T-BPPSIM) achieves a resolution enhancement of 7.6-fold compared to conventional fluorescence microscopy. By further applying the fluorescence emission difference (FED) technique to the surface plasmon-coupled emission (SPCE) signals coupled out by the RK configuration, the resolution is enhanced to exceed 8-fold, achieving a resolution below 30 nm. This method provides a technical foundation for high-fidelity imaging of nanoscale at cell membrane interfaces.