A high numerical aperture parabolic mirror as imaging device for confocal microscopy.

We explore the diffraction limited focusing and confocal imaging properties of a high NA parabolic mirror for confocal imaging and spectroscopy of nanoparticles and single molecules. Vector field calculations of the electric fields near focus for both linear and radially polarized illumination are discussed and show that the optical field can be similar tightly focused as in the case of a high NA objective lens. Furthermore they show that a high NA parabolic mirror allows an easy orientation of the polarization of the illuminating light in all spatial directions. The simulation of confocal imaging of single molecules is discussed and yields, that the use of radially polarized excitation light gives an easy access to their orientations.