Lateral beam shifts and depolarization upon oblique reflection from dielectric mirrors

TL;DR

This paper investigates how dielectric mirrors cause lateral beam shifts, shape distortion, and depolarization at oblique incidence, highlighting the importance of understanding these effects for optical experiments.

Contribution

It provides experimental and simulated analysis of beam shifts and depolarization effects in dielectric mirrors, emphasizing the need for vendor transparency.

Findings

Lateral beam shifts depend on wavelength, angle, and polarization.

Dielectric mirrors can cause significant beam-shape distortion.

Depolarization effects are observed at oblique incidence.

Abstract

Dielectric mirrors comprising thin-film multilayers are widely used in optical experiments because they can achieve substantially higher reflectance compared to metal mirrors. Here we investigate potential problems that can arise when dielectric mirrors are used at oblique incidence, in particular for focused beams. We found that light beams reflected from dielectric mirrors can experience lateral beam shifts, beam-shape distortion, and depolarization, and these effects have a strong dependence on wavelength, incident angle, and incident polarization. Because vendors of dielectric mirrors typically do not share the particular layer structure of their products, we designed and simulated several dielectric-mirror stacks, and then also measured the lateral beam shift from two commercial dielectric mirrors and one coated metal mirror. We hope that this paper brings awareness of the tradeoffs between dielectric mirrors and front-surface metal mirrors in certain optics experiments, and suggest that vendors of dielectric mirrors provide information about beam shifts, distortion, and depolarization when their products are used at oblique incidence.