We reveal the intrinsic meron pseudospin texture in momentum space in a photonic crystal slab, which can be directly observed as meron and antimeron spin texture by polarimetric study of high-order diffracted light from the system. This work is published in Physics Review Letters.
Spin textures, the spin configurations in either real space or momentum space, are of great interest in various fields of physics and are relevant to many nontrivial physical phenomena. Skyrmions, merons and antimerons are non-singular topological spin textures that have been extensively studied in various systems. Photons are massless spin-1 particles, thus skyrmion-related objects can emerge as transverse spin textures, i.e., polarization of photons as well.
In this work, we report meron and antimeron in momentum space using a honeycomb photonic crystal slab. The existence of such objects has not been previously noted either in electronic or photonic systems. Breaking the inversion symmetry of a honeycomb photonic crystal gaps out the Dirac cones at the corners of Brillouin zone. The spin textures of photonic bands near the gaps exhibit a meron or antimeron. Unlike the electronic systems, the spin texture of the photonic modes manifests directly in the polarization of the leakage radiation, as the Dirac points can be above the light line.
Our work highlights the significant opportunities of using photonic structures for the exploration of topological spin textures, with potential applications towards topologically robust ways to manipulate polarizations and other modal characteristics of light.
Fig. 1. The spin textures of the leakage radiation on the iso-frequency contours of the photonic band structure.