EAGER: Optical Negative Index Materials Using 3d Metals

University Of Massachusetts Lowell, Lowell MA

Investigators

Abstract

This work proposes to design and create a novel natural, principally non-composite, negative refraction index metamaterial based on 3d ferromagnetic metals (Fe, Ni) in the Mid-wavelength Infrared (MWIR) regime for applications in security screening, tunable bandpass filters, non-destructive testing, label-free techniques for biomolecules, and superlensing. In this design, we exploit novel internal microscopic molecular response mechanisms to obtain the negative index of refraction. We should emphasize that there are no other suggested analogous metamaterial designs in the optical domain based on the mechanism proposed herein. Our preliminary results show that, indeed, coupling between the electromagnetic wave and both plasmons and magnons exists in these materials, and this coupling ensures simultaneous permittivity and permeability responses, which can be adjusted to provide a negative index of refraction. Hence, we suggest both new materials as well as new mechanisms for the negative index effect. The major tasks proposed in this research include: 1) fabrication and characterization of these materials and 2) validation of the unique properties of the fabricated materials through experimental and theoretical studies. This is a bold novel idea of combining the two fields of solid state physics: plasmonics with magnonics to achieve the desirable negative refractive index effect in homogeneous materials and has the potential to transform this very popular area of and optics since all other optical NIMs are non-homogeneous. This radically new approach to obtaining optical negative index materials is novel in terms of both the target (negative refractive index), and the means (plasmonics and magnonics) of reaching this goal. Intellectual Merit: The successful validation of the proposed design would represent one of the first practical implementation of a homogenous, fully isotropic, and low-loss negative index THz metamaterial. We should stress that this principally homogeneous (or natural), metal-based medium has not been reported in the field of negative index of refraction metamaterials. Our proposed material has an advantage in fabrication over its composite counterparts, with respect to the difficulty in alignment, registration, and in creating multi-layer structures if one is to use these in actual applications (especially as scales become smaller for high frequency regimes). Consequently, these homogeneous materials are better suited for the realization of real-world applications. The major innovation of the proposed work lies in the creation of a novel type of negative index material based on metallic ferromagnets for the first time and the new mechanism which is exploited to obtain the negative index effect. Both of these innovations could transform the way optical negative index materials are designed. The non-composite, fully optically isotropic, and low-loss metamaterial, as is proposed here, may allow the implementation of various applications including, bandpass filters, frequency multipliers, THz sub-wavelength resolution imaging systems, molecular spectroscopy for biosensors, and security systems and make a great impact in the field of enhanced near-field imaging. Broader Impact: The successful validation of the proposed design would represent one of the first practical implementation of a homogenous, low-loss, metal-based negative index material in the MWIR. These metamaterials could potentially make a significant impact in the areas of personnel security screening, medical imaging, remote sensing, biomedicine, and sensors for high throughput screening. These applications could have important implications in for Homeland Security and drug discovery.