High-numerical-aperture optical microscopy and modern applications: introduction to the feature issue

Far-field polarization-based sensitivity to sub-resolution displacements of a sub-resolution scatterer in tightly focused fields

We present a system built to perform measurements of scattering-angle-resolved polarization state distributions across the exit pupil of a high numerical aperture collector lens. These distributions contain information about the three-dimensional electromagnetic field that results from the interaction of a tightly focused field and a sub-resolution scatterer. Experimental evidence proving that the system allows for high polarization-dependent sensitivity to sub-resolution displacements of a sub-resolution scatterer is provided together with the corresponding numerical results.

Simple fiber-optic confocal microscopy with nanoscale depth resolution beyond the diffraction barrier

A novel fiber-optic confocal approach for ultrahigh depth-resolution (<or=2 nm) microscopy beyond the diffraction barrier in the subwavelength nanometric range below 200 nm is presented. The key idea is based on a simple fiber-optic confocal microscope approach that is compatible with a differential confocal microscope technique. To improve the dynamic range of the resolving laser power and to achieve a high resolution in the nanometric range, we have designed a simple apertureless reflection confocal microscope with a highly sensitive single-mode-fiber confocal output. The fiber-optic design is an effective alternative to conventional pinhole-based confocal systems and offers a number of advantages in terms of spatial resolution, flexibility, miniaturization, and scanning potential. Furthermore, the design is compatible with the differential confocal pinhole microscope based on the use of the sharp diffraction-free slope of the axial confocal response curve rather than the area around the maximum of that curve. Combining the advantages of ultrahigh-resolution fiber-optic confocal microscopy, we can work beyond the diffraction barrier in the subwavelength (below 200 nm) nanometric range exploiting confocal nanobioimaging of single cell and intracellular analytes.