Second-order nonlinear optical metamaterials: ABC-type nanolaminates

TL;DR

This paper demonstrates the creation of second-order nonlinear optical metamaterials using non-metallic, centrosymmetric nanolaminates, breaking symmetry through stacking sequences, enabling low-loss nonlinear optical responses.

Contribution

It introduces the first realization of bulk nonlinear optical metamaterials from non-metallic constituents using atomic-layer deposition.

Findings

Successfully fabricated ABC-type nanolaminates with broken centrosymmetry

Demonstrated second-order nonlinear optical response in the metamaterials

First to realize bulk nonlinear optical metamaterials from non-metallic materials

Abstract

Structuring optical materials on a nanometer scale can lead to artificial effective media, or metamaterials, with strongly altered optical behavior. Metamaterials can provide a wide range of linear optical properties such as negative refractive index, hyperbolic dispersion, or magnetic behavior at optical frequencies. Nonlinear optical properties, however, have only been demonstrated for patterned metallic films which suffer from high optical losses. Here we show that second-order nonlinear metamaterials can also be obtained from non-metallic centrosymmetric constituents with inherently low optical absorption. In our proof-of-principle experiments, we have iterated atomic-layer deposition (ALD) of three different constituents, A = Al$_2$O$_3$, B = TiO$_2$ and C = HfO$_2$. The centrosymmetry of the resulting ABC stack is broken since the ABC and the inverted CBA sequences are not equivalent - a necessary condition for non-zero second-order nonlinearity. To the best of our knowledge, this is the first realization of a bulk nonlinear optical metamaterial.