Generation and experimental investigation of complex polarization topologies at the nanoscale

Light is a fascinating ‘playground’, which is amazingly rich, especially if its polarization is taken into account. When light is highly confined, for instance, by tight focusing, the polarization can form three-dimensional, spatially varying landscapes leading to complex phase and field distributions as well as extraordinary topologies. One of these 3D topologies might resemble a Möbius strip – a geometrical object that has only one side and one boundary.

Proposed theoretically for intersecting collimated light beams about a decade ago by I. Freund [1], we now succeeded in experimentally proving the existence of these highly unusual objects for the first time [2]. In this joint project, we created optical polarization Möbius strips in the lab by focusing a superposition [3] of two light beams tightly. Utilizing a recently developed coherent nano-probing approach [4], we were able to measure the distribution of the electric field in the focal plane with deep sub-wavelength spatial resolution. By retrieving the local polarization ellipses from the electric field information, we unveiled the hidden Möbius strips formed by the ellipse axes.

References:

[1] I. Freund, Cones, spirals, and Möbius strips, in elliptically polarized light, Opt. Commun. 249, 7 (2005).
[2] T. Bauer, S. Orlov, U. Peschel, P. Banzer and G. Leuchs, Nanointerferometric amplitude and phase reconstruction of tightly focused vector beams, Nature Photonics 8, 23 - 27 (2014)
[3] L. Marrucci, C. Manzo, D. Paparo, Optical Spin-to-Orbital Angular Momentum Conversion in Inhomogeneous Anisotropic Media, Phys. Rev. Lett. 96, 163905 (2006)..
[4] T. Bauer, P. Banzer, E. Karimi, S. Orlov, A. Rubano, L. Marrucci, E. Santamato, R. W. Boyd and G. Leuchs, Observation of optical polarization Möbius strips, Science 347, 964-966 (2015).

Project leaders:

Peter Banzer (MPL), peter.banzer@mpl.mpg.de
Ebrahim Karimi (uOttawa), ekarimi@uottawa.ca

Other senior researchers:

Robert W. Boyd (uOttawa)
Gerd Leuchs (MPL)