Subwavelength-sized plasmonic structures for wide-field optical microscopic imaging with super-resolution

Abstract

We propose a wide-field super-resolved optical microscopic imaging technique based on subwavelength slit arrays embedded in a thin silver film to generate surface plasmon (SP) standing wave interference patterns. These fringes carrying high spatial frequency information serve as excitation profiles to excite the nanoscale fluorescence objects. The super-resolved fluorescence density distribution is reconstructed from a weight sum of a series of fluorescence images with differently phase-shifted SP standing wave illumination. Simulation and experimental results show that the lateral resolution of the reconstructed fluorescence density image is enhanced by 0.28 λ SP in two dimensions, which is twofold better than that of conventional high numerical aperture fluorescence microscopy. This technique benefits from a grating coupler to offer a simple way for the generation and phase shift of SP standing wave excitation profiles in two dimensions. The flat configuration, wide field, and noninvasive nature make this approach suitable for real-time analyzing the fine details of bio-samples in biochip applications.