Index of refraction of any medium is defined as the proportion between the light of speed in vacuum and in the investigated medium. Negative refractive index metamaterials sciencedirect. Brief overview of recent developments on negative phase. An illustrative case study demonstrates that in general the spectrum divides into five distinct regions. The larger the index, the slower the light travels through that medium. Refractive index formula refractive index of glass. Diverse approaches for achieving nr and nim are covered, such as using photonic crystals, phononic crystals, splitring resonators srrs and continuous media, focusing of waves, guidedwave behavior, and nonlinear effects.
Osa negative index of refraction in optical metamaterials. Recently, different groups observed indirectly10 negative at the thz region. Osa metamaterials with gradient negative index of refraction. The negative index of refraction demystified iopscience. The contributors to this book prepared their chapters coming from very diversi. It may eventually be possible, if not currently feasible, to produce a structure with a substantial negative optical refractive index.
It defines how much a light ray can be bent when it enters from one medium to the other. This book deals with the subject of optical and electronic negative refraction nr and negative index materials nim. Index of refraction article about index of refraction by. The optical density of a medium represents the ability to refract light. Part of the nato science series book series naii, volume 89. Appearence with negative index of refraction physics forums. This website gives refractive indices of various elements, compounds, and optical materials as a function of wavelength with references. That extends the recently studied case of propagation in mediums for which the relative.
This demonstration of a previously unexploited electromagnetic em property proved the importance of engineered materials and has resulted in an extraordinary amount of continued development by scientists working in optics, electromagnetism, physics. In the 1960s, a russian scientist named vesalago 1 suggested that a negative refractive index might be possible and he investigated theoretically what would happen if a material had a negative refractive index. In addition, the refractive index also provides a measure of the deflection of a beam of light as it crosses the interface between. Metamaterials are artificially fabricated structures that have new. Dec 04, 2006 i never said you would find such a material in nature. Is there a list of materials sorted by their index of refraction. This is the first documented use of refractive indices and is described by snells law of refraction, n 1 sin. A doubleperiodic array of pairs of parallel gold nanorods is shown to have a negative refractive index in the optical range. The law of refraction is also called snells law after the dutch mathematician willebrord snell 15911626, who discovered it in 1621. Index of refraction definition of index of refraction by. A slab of the negative refractive index metamaterial has a focal length that can be tuned by changing the gradient of the negative refractive index. The negative refraction effect that we describe depends only on the refractive index of the dielectric material and on the geometric factors used in twodimensional photonic crystals. Ultrafast refractive index control of a terahertz graphene metamaterial. Snells experiments showed that the law of refraction was obeyed and that a characteristic index of refraction n could be assigned to a given medium.
The index of refraction, n, depends not only on the material of the medium through which light passes, but the wavelength of light. Negative index of refraction in optical metamaterials. A negative index metamaterial causes light to refract, or bend, differently than in more common positive index materials such as glass lenses negative index metamaterial or negative index material nim is a metamaterial whose refractive index for an electromagnetic wave has a negative value over some frequency range. Martin w mccall1,4, akhlesh lakhtakia2 and werner s weiglhofer3. The definition of negative phase velocity npv propagation in eq. A thin metal film pierced with holes of appropriate size or spacing between them can be used as a. We study electromagnetic wave propagation in mediums in which the effective relative permittivity and the effective relative permeability are allowed to take any value in the upper half of the complex plane. Such behavior results from the plasmon resonance in the pairs of nanorods for both the electric and the magnetic components of light.
If both e and m are negative, then also the index of refraction n is negative 10, 11. The others havent actually answered your real question what primary properties of a material give it an index of refraction. As you mention, an artificial metamaterial can display a negative index of refraction. Full text of positive and negative gooshanchen shifts and. It was cowritten by john pendry, who has been credited for inventingdiscovering the metamaterial that exhibits this property. Top american libraries canadian libraries universal library community texts project gutenberg biodiversity heritage library childrens library. The negative index of refraction demystified view the table of contents for this issue, or go to the journal homepage for more home search collections journals about contact us my iopscience you may also be interested in. We study electromagnetic wave propagation in mediums in which the effective relative permittivity and the effective relative permeability are allowed to take. Springer series in materials science 98 physics of negative. The index of refraction of the first and second media is denoted by n 1 and n 2 respectively, and. Negativeindex metamaterial or negativeindex material nim is a metamaterial whose refractive index for an electromagnetic wave has a negative value over some frequency range nims are constructed of periodic basic parts called unit cells, which are usually significantly smaller than the wavelength of the externally applied electromagnetic radiation. My question is, if permittivity and permeabilitity of a material is negative then the end product, according to the above equation, should be positive.
Im going to answer this from a more interesting perspective, hopefully the perspective you intended. The speed of light is less due to the smaller refractive index in a vacuum when comparing with all other media. Refractive index, also called index of refraction, measure of the bending of a ray of light when passing from one medium into another. The negative index of refraction demystified internet archive. Negative refractive index metamaterials nrm are artificial composites, characteri zed by subwavelength features and negative effective value of re fractive index 2, 3. Jan 15, 2007 this article is as good as any tutorial on the physics of negative index of refraction. The refractive index determines how much light is bent, or refracted, when entering a material. If i is the angle of incidence of a ray in vacuum angle between the incoming ray and the perpendicular to the surface of a medium, called the normal and r is the angle of refraction angle between the ray in. The index of refraction provides a measure of the speed of an em wave as it propagates within a material.
We propose a new metamaterial with a gradient negative index of refraction, which can focus a collimated beam of light coming from a distant object. Preface are referred to in the book as lefthanded, negativerefractiveindex or negative index, and. One consequence of this difference in speed is that when light goes from one medium to another at an angle, the propagation vector in the new medium has a different angle with respect to the normal. Ultrafast refractive index control of a terahertz graphene. Weiglhoferthe negative index of refraction demystified. Jan 21, 2000 the refractive index is a basic property of material, accurate values of which are often required to interpret various types of spectroscopic data. Digital handheld refractometers by aiming a light beam into any substantial body of liquid ethane or methane, the ssp will attempt to record the index of refraction of the fluid, another indication of its density. My question is about how such a structure would appear versus the. This means the negative refraction of the electro magnetic wave passing through the boundary of two materials, one with positive and the second with negative n negative snells law. First, the physics of the phenomenon of negative refraction. When light changes its medium, one possible consequence is refraction, a change in direction. The negative index of refraction demystified martin w mccall 1,4, akhlesh lakhtakia 2 and werner s weiglhofer 3 published 8 may 2002 european journal of physics, volume 23, number 3. Pdf the negative index of refraction demystified researchgate.
Snells law specifies the relationship between the incident and refracted angles. The ratio of the speed of light in a vacuum to the speed of light in a medium under consideration. Index of refraction financial definition of index of refraction. Citeseerx the negative index of refraction demystified. What determines the refractive index of a material. Wave propagation in a slab with negative index of refraction. A commonly used em parameter is that of the index of refraction, which is defined as n. The negative index of refraction demystified article pdf available in european journal of physics 233 april 2002 with 126 reads how we measure reads. Experimental demonstration of negative index of refraction. If the speed of light reduces, the index of refraction increases. In most of the thz experiments1012 only one layer of srrs was fabricated on a substrate and the. Below we report our experimental observation of a negative refractive index for the optical range, specifically, for the wavelengths close to 1. Among the possible effects suggested were negative refraction, negative doppler shift which we wont discuss here, and planar focusing.
A covariant theory of negative phase velocity propagation. The index of refraction, n, is the ratio of the speed of light in a vacuum, c, to the speed of light in a medium, c. Citeseerx document details isaac councill, lee giles, pradeep teregowda. A materials refractive index depends on which wavelength of light you are considering. A general condition is derived for the phase velocity to be oppositely directed to the power flow. Ideas for potential applications of metamaterials with negative. The refractive index is retrieved from direct phase and amplitude measurements for transmission and reflection, which are all in. Metamaterials with negative real permittivity and permeability possess. Many groups were able to fabricate1,2,58 nims with an index of refraction n. If two negative numbers multiplied should give a positive number. Pdf we study electromagnetic wave propagation in mediums in which the effective relative permittivity and the effective relative permeability. The pa202 model includes dual scales for measuring both brix and index of refraction, as high as 85 brix or 1. Numerical simulations were performed as a function of the filling fraction and the relative index of refraction, ny defined as the ratio between the index of refraction of the scatterers and the surrounding media noted n and n0.
Still, the ultimate goal of negative refraction was not accomplished in these experiments. Simulation of electromagnetic fields in double negative. This means that refraction at the interface between a positiveindex material and a negativeindex material would tear the wave apart, leaving no single negatively refracted wave. Apr 23, 2002 we study electromagnetic wave propagation in mediums in which the effective relative permittivity and the effective relative permeability are allowed to take any value in the upper half of the complex plane. The refractive index of a medium is defined as how the light travels through that medium.
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