Optical Metamaterials at Near and Mid IR Range Fabricated by Nanoimprint Lithography

TL;DR

This paper reports the design, fabrication, and characterization of optical metamaterials operating at near-IR and mid-IR frequencies using nanoimprint lithography, demonstrating negative refractive index and resonances in a cost-effective manner.

Contribution

It introduces a novel application of nanoimprint lithography for fabricating optical metamaterials with negative index properties at IR wavelengths.

Findings

Near-IR fishnet structure exhibits negative permittivity and permeability near 1.7 um.

Mid-IR L-shaped resonators show negative permittivity and permeability at 3.7 um and 5.25 um.

Optical properties match theoretical predictions.

Abstract

Two types of optical metamaterials operating at near-IR and mid-IR frequencies, respectively, have been designed, fabricated by nanoimprint lithography (NIL), and characterized by laser spectroscopic ellipsometry. The structure for the near-IR range was a metal/dielectric/metal stack "fishnet" structure that demonstrated negative permittivity and permeability in the same frequency region and hence exhibited a negative refractive index at a wavelength near 1.7 um. In the mid-IR range, the metamaterial was an ordered array of four-fold symmetric L-shaped resonators (LSRs) that showed both a dipole plasmon resonance resulting in negative permittivity and a magnetic resonance with negative permeability near wavelengths of 3.7 um and 5.25 um, respectively. The optical properties of both metamaterials are in agreement with theoretical predictions. This work demonstrates the feasibility of designing various optical negative-index metamaterials and fabricating them using the nanoimprint lithography as a low-cost, high-throughput fabrication approach.