No abstract

Super-resolution microscopy by microspheres emerged as a simple and broadband imaging technique; however, the mechanisms of imaging are debated in the literature. Furthermore, the resolution values were estimated based on semi-quantitative criteria. The primary goals of this work are threefold: i) to quantify the spatial resolution provided by this method, ii) to compare the resolution of nanoplasmonic structures formed by different metals, and iii) to understand the imaging provided by microfibers. To this end, arrays of Au and Al nanoplasmonic dimers with very similar geometry were imaged using confocal laser scanning microscopy at λ = 405 nm through high-index (n~1.9-2.2) liquid-immersed BaTiO₃ microspheres and through etched silica microfibers. We developed a treatment of super-resolved images in label-free microscopy based on using point-spread functions with subdiffraction-limited widths. It is applicable to objects with arbitrary shapes and can be viewed as an integral form of the super-resolution quantification widely accepted in fluorescent microscopy. In the case of imaging through microspheres, the resolution ~λ/6-λ/7 is demonstrated for Au and Al nanoplasmonic arrays. In the case of imaging through microfibers, the resolution ~λ/6 with magnification M~2.1 is demonstrated in the direction perpendicular to the fiber with hundreds of times larger field-of-view in comparison to microspheres.

We fabricated thin-films made from polydimethylsiloxane (PDMS) with embedded high-index (n~1.9-2.2) microspheres for super-resolution imaging applications. To control the position of microspheres, such films can be translated along the surface of the nanoplasmonic structure to be imaged. Microsphere-assisted imaging, through these matrices, provided lateral resolution of ~λ/7 in nanoplasmonic dimer arrays with an illuminating wavelength λ=405 nm. Such thin films can be used as contact optical components to boost the resolution capability of conventional microscopes.