Dual-mode super-resolution imaging with stimulated emission depletion microscopy and fluorescence emission difference microscopy.

Dual-mode super-resolution imaging system with two different super-resolution imaging methods, STED and FED, is presented. Electrical shutters controlled by the host computer are introduced to switch the two imaging modes. Principles of both methods are analyzed theoretically, and enhancements in the lateral resolution and SNR are demonstrated theoretically and experimentally. Results show that both imaging methods offered by the proposed system can break the diffraction barrier. Furthermore, the presented system provides a meaningful way to image fluorescent samples by a corresponding imaging mode according to the specific characteristics of samples analyzed for study. For samples that can endure high-power illumination, it is appropriate to use the STED mode to achieve a better resolution, while for samples that are vulnerable to high intensity, the FED method is a better choice because no high-power beam is needed, and the FED method can provide better resolution than STED when no high-power beam is allowed. The flexible switching of the two super-resolution imaging modes can help researchers to make most of the advantages of each imaging method. It is believed that the presented system has the potential to be widely used in future nanoscale investigations.