Towards the standing wave surface plasmon resonance fluorescence microscopy

Surface plasmons are coherent oscillations of the free electrons on metal surface which can be used to improve the excitation efficiency of fluorophores due to increased field enhancement. Surface plasmon resonance fluorescence (SPRF) microscopy is a wide-field optical imaging technique that utilizes the evanescent electromagnetic field of surface plasmons to excite fluorophores near to a surface of a metal film. With the same excitation power, the field enhancement effect of the surface plasmon resonance (SPR) leads to strong fluorescence emission and thus increases the signal to noise ratio of detection. However, there have been few studies on the image formation process for SPRF in terms of its point-spread function. By imaging fluorescent microspheres with size below the diffraction limit, we obtained the point-spread function for SPRF. The SPR enhancement is confirmed by back-focal-plane imaging with various incidence angles of the excitation beam. Furthermore, we will investigate the potential of resolution enhancement by generating standing wave with two symmetric incident excitation beams toward the standing-wave surface plasmon resonance fluorescence (SW-SPRF) microscopy.