Orientation determination of single molecules by highly focused generalized cylindrical vector beams

Abstract

The orientation of the dipole moment, which is one of important parameters in single-molecule fluorescence spectroscopy, is determined by highly focused generalized cylindrical vector beams combined with a confocal far-field microscope. A generalized cylindrical vector beam can be decomposed into a linear superposition of radially polarized and azimuthally polarized components and the ratio of the radial and longitudinal components of the focal electric field can be adjusted by changing the polarization direction. As compared to the case of a radially polarized incident beam, numerical results demonstrate that fluorescence intensity difference among single molecules with different orientations can be effectively overcome for a particular polarization direction of the generalized cylindrical vector beam, which may increases the signal-to-noise ratio of the practical experiments and then ease the difficulty in orientation determination of single molecules.