Photonic metamaterials by direct laser writing and silver chemical vapour deposition

Metamaterials are artificial materials that-unlike natural substances-enable magnetism to be achieved at optical frequencies(1-3). The vast majority of photonicmetamaterials(4,5) has been fabricated by electron-beam lithography and evaporation of metal films, both of which are well-established two-dimensional (2D) technologies. Although stacking of three(6) or four(7) functional layers made using these methods has been reported, a truly 3D fabrication approach would be preferable for 3D photonic metamaterials. Here, we report first steps in this direction by using a combination of direct laser writing(8,9) and silver chemical vapour deposition(10,11)-the 3D analogues of electron-beam lithography and evaporation, respectively. The optical characterization of a planar test structure composed of elongated split-ring resonators is in good agreement with theory. Retrieval of the effective optical parameters reveals the importance of bi-anisotropy. Once suitable theoretical blueprints are available, our fabrication approach will enable rapid prototyping of truly 3D photonic metamaterials.