Type-II Dirac photonic lattices

TL;DR

This paper demonstrates the design and analysis of type-II Dirac cones in Lieb-like photonic lattices, providing a feasible platform for studying topological and nonrelativistic phenomena in optics.

Contribution

It introduces a novel photonic lattice design exhibiting type-II Dirac cones, emphasizing the role of lattice symmetry over refractive index changes.

Findings

Observation of type-II Dirac cones in photonic lattices

Analysis of conical diffraction and Klein tunneling phenomena

Experimental feasibility of the proposed lattice design

Abstract

Different from the Fermi surface of the type-I Dirac semimetal being a point, that of the type-II Dirac semimetal is a pair of crossing lines because the Dirac cone is tilted with open and hyperbolic isofrequency contours. As an optical analogy, type-II Dirac photonic lattices have been also designed. Here, we report type-II Dirac cones in Lieb-like photonic lattices composed of identical waveguide channels, and the anisotropy of the band structure is due to neither the refractive index change nor the environment, but only the spatial symmetry of the lattice; therefore, the proposal is advantage and benefits experimental observation. Conical diffractions and Klein tunneling in the parametric type-II photonic lattice are investigated in detail. Our results provide a simple and experimental feasible platform to study two-dimensional topological photonic and other nonrelativistic phenomena around type-II Dirac cones.