Physical Origins of Extreme Cross-Polarization Extinction in Confocal Microscopy

Abstract

Confocal microscopy is an essential imaging tool for biological systems, solid-state physics and nanophotonics. Using confocal microscopes allows performing resonant fluorescence experiments, where the emitted light has the same wavelength as the excitation laser. These challenging experiments are carried out under linear cross-polarization conditions, rejecting laser light from the detector. In this work, we uncover the physical mechanisms that are at the origin of the yet-unexplained high polarization rejection ratio which makes these measurements possible. We show in both experiment and theory that the use of a reflecting surface (i.e., the beam splitter and mirrors) placed between the polarizer and analyzer in combination with a confocal arrangement explains the giant cross-polarization extinction ratio of 108 and beyond. We map the modal transformation of the polarized optical Gaussian beam. We find an intensity “hole” in the reflected beam under cross-polarization conditions. We interpret this hole as a manifestation of the Imbert-Fedorov effect, which deviates the beam depending on its polarization helicity. This result implies that this topological effect is amplified here from the usually observed nanometer to the micrometer scale due to our cross-polarization dark-field methods. We confirm these experimental findings for a large variety of commercially available mirrors and polarization components, allowing their practical implementation in many experiments.Received 29 April 2020Revised 14 January 2021Accepted 15 February 2021DOI:https://doi.org/10.1103/PhysRevX.11.021007Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasNanophotonicsPolarization of lightAtomic, Molecular & Optical

Locations

• Physical Review X - View - PDF
• arXiv (Cornell University) - View - PDF
• DOAJ (DOAJ: Directory of Open Access Journals) - View
• DataCite API - View