INDIAN INSTITUTE OF TECHNOLOGY ROORKEE

Metamaterials : Negative refractive index property

By

Rahul Choudhary(12118062)Sourabh Hirau(12118077)

Udit Kumar(12118084)

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Overview

Introduction

Artificial magnetic materials

Applications

Negative Refractive Index

Fabrication

Conclusions

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Introduction

• A metamaterial is a micro/nano composite of periodic or non-periodic structure, whose function is due to both the artificial cellular architecture and chemical composition.

• These materials exhibit some properties, that are not usually shown by the naturally occurring material generally.

• 1st Stage observation and investigation of the physical phenomena in nature

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Introduction

• 2nd stage - design of From natural to complex EM materials artificial materials to imitate the nature at lower frequencies.

• 3rd Stage - Measurement of electromagnetic parameters of The paradigmatic example of chiral the some chiral materials realized doping a host dielectric through metallic or synthetic helices

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Introduction

• 4th Stage - investigation of the exciting features of metamaterials to:

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Science Behind all these

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Applications

1. Negative Index2. Artificial Magnetism3. Chiral Metamaterials4. Light antenna5. Absorber6. Superlens7. Cloaking devices8. Seismic protection

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Artificial magnetic materials

• Natural materials with unusual electric response (e.g. exhibiting a negative polarizability) already exist at optical frequencies (e.g. noble metals).

• Plasmas are another interesting example of materials with unusual electric response.

• Artificial plasmas have been studied since the 60s using the so-called parallel-plate and wire medium.

• Since the beginning of the metamaterial era, these studies came back into play.

• Negative permittivity has been observed in nature but negative permeability is quiet a sticky issue to simple exist in nature.

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Split Ring Resonator

Pendry J B, Holden A J, Robbins D J and Stewart W J 1999 IEEE Trans. Microw. Theory Tech. 47 2075–84

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Negative Refractive Index

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Superlens

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Fabrication

• There are various methods Fabrication and Each have their own advantages and drawbacks.

1. )Fabrication of 2D metamaterials A. Electron-beam lithography (EBL) B. Rapid prototyping: focused-ion beam (FIB) milling C. Large-scale fabrication: interference lithography. D. High-resolution large-scale fabrication: nanoimprint lithography (NIL).2. )Fabrication of 3D metamaterials A. Making multiple layers B. Two-photon-photopolymerization (TPP) technology C. Fabrication of complex 3D structures D. 3D structures by nanoimprint

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First experimentally obtained optical negative-index metamaterials: (a) schematic of an array of paired Au

nanorods separated by a layer of SiO2 together with

(b) field-emission scanning electron microscope images of the fabricated array (Au(50 nm)–SiO2(50 nm)–Au(50 nm) stacks), where a negative refractive index is achieved at telecommunication wavelengths

V.M. Shalaev, W. Cai, U.K. Chettiar, H.K. Yuan, A.K. Sarychev, V.P. Drachev, A.V. Kildishev, Negative index of refraction in optical metamaterials, Opt. Lett. 30 (2006) 3356

Fabrication of 2D metamaterials

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c) schematic of a multilayer structure consisting of a dielectric layer between two metal films perforated with a hole on a glass substrate

(d) scanning electron microscope image of the fabricated structure (Au(30 nm).Al2O3(60 nm).Au(30 nm) stack, 838 nm pitch, 360 nmhole diameter), which exhibits a negative index at about λ = 2μm

S. Zhang,W. Fan, N.C. Panoiu, K.J. Malloy, R.M. Osgood, S.R.J. Brueck, Experimental demonstration of near-infrared negativeindex metamaterials, Phys. Rev. Lett. 95 (2005) 137404

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Fabrication of 3D metamaterials

(a) Schematic (side view) of the metamaterial layers under investigation together with

(b) electron micrographs of fabricated structures with N-functional layers (400-nm scale bar

S. Zhang,W. Fan, N.C. Panoiu, K.J. Malloy, R.M. Osgood, S.R.J. Brueck, Optical negative-index bulk metamaterials consisting of 2D perforated metal–dielectric stacks, Opt. Express 14 2006) 6778.

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Schematic of two possible ways of making multiple metal–dielectric layers: (a) the standard deposition—lift-off procedure[64] that provides trapezoidal final structures and has a total deposited thickness limitation (it has to be at least 15–20% less than the thickness of the resist for a successful lift-off process) together with

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(b) the proposed etch-based procedure where a thick planar stack of metal–dielectric layers is deep etched to create a 3D metamaterialslab.

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Conclusions

• Metamaterials is one of the emerging field and many aspects of this field are still unexplored.

• Certainly Metamaterials assembly can be in micro size range but nano size range give them the functionality to work in optical range.

• Simple concepts of inductance and capacitor coupled with wonderful Maxwell relations gives us a whole new material which is engineered at nanoscale.

• Basically most of the fabrication routs are top down methods but few are bottom up methods (actually little bit of both).

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References

[1] V.G. Veselago, The electrodynamics of substances with simultaneously negative values of å and ì, Sov. Phys. Usp. 10 (1968) 509.[2] V.G. Veselago, L. Braginsky, V. Shklover, Ch. Hafner, Negative refractive index materials, J. Comput. Theor. Nanosci. 3 (2006) 189.[3] J.B. Pendry, Negative refraction makes a perfect lens, Phys. Rev.Lett. 85 (2000) 3966[4] Boltasseva, A., & Shalaev, V. M. (2008). Fabrication of optical negative-index metamaterials: Recent advances and outlook. Metamaterials, 2(1), 1–17. http://doi.org/10.1016/j.metmat.2008.03.004

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