Longitudinal Field Modes Probed by Single Molecules

TLDR

Single molecules with fixed absorption dipole moments probe the longitudinal field. The study shows that a radially polarized beam generates a strong, localized, nonpropagating longitudinal field whose energy density exceeds the transverse field by more than twice, can be mapped in three dimensions using single molecules with fixed dipole moments, and carries no momentum or energy transport.

Abstract

We demonstrate that a strong longitudinal, nonpropagating field is generated at the focus of a radially polarized beam mode. This field is localized in space and its energy density exceeds the energy density of the transverse field by more than a factor of 2. Single molecules with fixed absorption dipole moments are used to probe the longitudinal field. Vice versa, it is demonstrated that orientations of single molecules are efficiently mapped out in three dimensions by using a radially polarized beam as the excitation source. We also show that there is no momentum or energy transport associated with the longitudinal field.