Circular birefringence in crystal optics

TL;DR

This paper explores how crystal symmetry and space-time considerations influence optical activity and gyrotropy in crystals, providing a relativistic perspective on their electrodynamic properties.

Contribution

It offers a relativistic justification for optical activity phenomena and links space-time symmetries to crystal gyrotropy and wave degeneracies.

Findings

Degeneracies of forward and backward waves are due to PT symmetry.

Space-time symmetry considerations classify static property tensors.

Relativistic analysis explains optical activity in crystal classes.

Abstract

In crystal optics the special status of the rest frame of the crystal means that space-time symmetry is less restrictive of electrodynamic phenomena than it is of static electromagnetic effects. A relativistic justification for this claim is provided and its consequences for the analysis of optical activity are explored. The discrete space-time symmetries P and T that lead to classification of static property tensors as polar or axial, time-invariant (-i) or time-change (-c) are shown to be connected by orientation considerations. The connection finds expression in the dynamic phenomenon of gyrotropy in certain, symmetry determined, crystal classes. In particular, the degeneracies of forward and backward waves in optically active crystals arise from the covariance of the wave equation under space-time (PT) reversal.