Possible Realization of Optical Quadratic and Dirac Points in Woodpile Photonic Crystals

TL;DR

This paper demonstrates that woodpile photonic crystals can host exotic fermion-like relativistic degeneracies, including Dirac nodal lines and quadratic points, enabling optical Dirac physics at visible frequencies.

Contribution

It reveals the presence of Dirac and quadratic degeneracies in woodpile photonic crystals, a novel finding for all-dielectric optical materials.

Findings

Discovery of Dirac nodal line and quadratic point in woodpile photonic crystals

Deformation leads to emergence of type-II Dirac points

Type-II Dirac points exhibit giant birefringence in experiments

Abstract

The simulation of fermionic relativistic physics, e.g., Dirac and Weyl physics, has led to the discovery of many unprecedented phenomena in photonics, of which the optical-frequency realization is, however, still challenging. Here, surprisingly, we discover that the woodpile photonic crystals commonly used for optical frequency applications host exotic fermion-like relativistic degeneracies: a Dirac nodal line and a fourfold quadratic point, as protected by the nonsymmorphic crystalline symmetry. Deforming the woodpile photonic crystal leads to the emergence of type-II Dirac points from the fourfold quadratic point. Such type-II Dirac points can be detected by its anomalous refraction property which is manifested as a giant birefringence in a slab setup. Our findings provide a promising route towards 3D optical Dirac physics in all-dielectric photonic crystals.