Determination of the three-dimensional orientation of single molecules

A simple method for real-time determination of the full three-dimensional orientation of the emission dipole of single molecules is presented. Introduction of a π phase step in the back focal plane of the collector lens breaks the inherent symmetry, allowing the longitudinal dipole component to be measured. Experimental tolerances and the consequence of a nonzero bandwidth emission spectrum are also discussed. The scheme also allows for the longitudinal component of an electric field to be found experimentally.