Electrodeposited Negative Index Metamaterials with Visible and Near Infrared Response

Negative index metamaterials have revolutionized the field of photonics because of their unconventional electromagnetic properties absent in naturally occurring materials. It remains a challenge however, to achieve strong negative refractive index at optical frequencies over large areas in a device compatible fashion. In this work, a scalable method for the straightforward production of fishnet-like negative index metamaterials combining soft nanoimprinting and electrodeposition is reported. In four simple steps, 2D arrays of pillars surrounded by metal-insulator-metal stacks made of gold and air gaps are created. The proper design of the geometrical features leads to negative indices from the visible to the near infrared, with values from -1.2 at 700 nm to -2.8 at 910 nm. The metamaterials are prepared on transparent conductive electrodes hence ready for device implementation. In addition, the nanostructures display high optical quality, which is corroborated with numerical simulations under normal and oblique incidence. As a proof of concept, the accessibility to the porosity of the metamaterial by studying the spectral changes produced when infiltrating different liquids through the metallic layers is demonstrated. The resonant wavelength increasing with the refractive index of the media makes the metamaterials potential platforms for both negative index structures and optical sensors.