Optical phase shifts and diabolic topology in Mobius-type strips

TL;DR

This paper investigates optical phase shifts in light traveling along non-planar twisted strips, revealing unique topological effects like diabolic crossings, especially prominent in Möbius strips, with potential implications for optical and topological physics.

Contribution

It introduces a novel analysis of optical phase shifts using a Schrödinger equation framework, highlighting the special topological features of Möbius strips and their relation to curvature and phase behavior.

Findings

Diabolic crossings occur at inflexion points where curvature vanishes.

Möbius strips exhibit a minimal phase shift at a critical width.

The effective Hamiltonian eigenvalues relate directly to the local curvature.

Abstract

We compute the optical phase shifts between the left and the right-circularly polarized light after it traverses non-planar cyclic paths described by the boundary curves of closed twisted strips. The evolution of the electric field along the curved path of a light ray is described by the Fermi-Walker transport law which is mapped to a Schr\"{o}dinger equation. The effective quantum Hamiltonian of the system has eigenvalues equal to $0, \pm \kappa$, where $\kappa$ is the local curvature of the path. The inflexion points of the twisted strips correspond to the vanishing of the curvature and manifest themselves as the diabolic crossings of the quantum Hamiltonian. For the M\"{o}bius loops, the critical width where the diabolic geometry resides also corresponds to the characteristic width where the optical phase shift is minimal. In our detailed study of various twisted strips, this intriguing property singles out the M"{o}bius geometry.