Topological Photonic Phase in Chiral Hyperbolic Metamaterials

Abstract

Recently, the possibility of achieving one-way backscatter immune transportation of light by mimicking the topological properties of certain solid state systems, such as topological insulators, has received much attention. Thus far, however, demonstrations of nontrivial topology in photonics have relied on photonic crystals with precisely engineered lattice structures, periodic on the scale of the operational wavelength and composed of finely tuned, complex materials. Here we propose a novel effective medium approach towards achieving topologically protected photonic surface states robust against disorder on all length scales and for a wide range of material parameters. Remarkably, the nontrivial topology of our metamaterial design results from the Berry curvature arising from the transversality of electromagnetic waves in a homogeneous medium. Our investigation therefore acts to bridge the gap between the advancing field of topological band theory and classical optical phenomena such as the spin Hall effect of light. The effective medium route to topological phases will pave the way for highly compact one-way transportation of electromagnetic waves in integrated photonic circuits.

Optical Gyrotropy from Axion Electrodynamics in Momentum Space

“…To date, this research has focused mainly on intricately fabricated metamedia in which response functions vary periodically on the scale of the optical wavelength. An example of a topological photonic state that can be created in this way is an analogue of the quantum Hall effect [44], but interfaces between conventional materials, which require less difficult fabrication, can also support topological interface states [45,46]. However, in Ref.…”

Field-effect induced tunability in hyperbolic metamaterials

“…Photonic analogues of topological insulators, in other words photonic materials that support non-trivial topologically protected states against back-scattering, have been realized with helical waveguides in a honeycomb lattice [16], by engineering the dispersion characteristics of photonic crystals. Theoretical studies suggest other configurations for realization of such protected states like chiral metamaterials with equal values of electric permittivity and magnetic permeability [17], or with chiral hyperbolic metamaterials [18] or with index-near-zero (which can be generalized to effective electric permittivity or magnetic permeability near-zero) metamaterials [19,20]. The latter idea arises from the consideration that Dirac-like dispersion cones can be realized in a linear dispersion regime where the metamaterial effective parameters approach zero, allowing for topological transitions to occur in metamaterials.…”

Hyperbolic Weyl Point in Reciprocal Chiral Metamaterials

“…The exploration of Weyl point in metamaterials as described by homogeneous effective material parameters is of fundamental interest since the wavevector space 4 of such meta-material is non-compact, which is in contrast with the wavevector space of periodic systems which is always topologically compact. [22] As a result, there is significant qualitative difference between the topological properties of the bands for meta-materials and photonic crystals as we will discuss in this paper.…”