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Topic: Negative refractive index

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	Refractive index - Wikipedia, the free encyclopedia
		The refractive index of a material is the factor by which the phase velocity of electromagnetic radiation is slowed relative to vacuum.
		The refractive index of certain media may be different depending on the polarization and direction of propagation of the light through the medium.
		If the refractive index of a medium is not constant, but varies gradually with position, the material is known as a gradient-index medium and is described by gradient index optics.
	en.wikipedia.org /wiki/Refractive_index (1120 words)

	Bambooweb: Refractive index
		The refractive index of a material at a particular frequency is the factor by which electromagnetic radiation of that frequency is slowed down (relative to vacuum) when it travels inside the material.
		For a non-magnetic material, the square of the refractive index is the dielectric constant $\epsilon (sometimes multiplied by \epsilon_0, the permittivity of free space).$
		Sometimes the refractive index is defined as a complex number, with the imaginary part of the number representing the absorption of the material.
	www.bambooweb.com /articles/r/e/Refractive_index.html (853 words)

	Refraction (Site not responding. Last check: 2007-10-15)
		Refraction is the change in direction of a wave due to a change in velocity.
		Refraction is also responsible for rainbows and for splitting up of white lightinto a rainbow-spectrum as it passes through a glass prism.
		Glasshas a higher refractive index than air and the different frequencies of light travel at different speeds (dispersion), causing them to be refracted at different angles.The different frequencies correspond to different colours observed.
	spanish.therfcc.org /refraction-24575.html (403 words)

	Light bends the wrong way
		This effect is known as refraction, controlled by a property of the materials known as their refractive index.
		Most materials have a refractive index greater than 1, which means that as light enters the material from air, the angle of the ray in the material will be more nearly "normal" (perpendicular) to the surface than it was before it entered.
		Refractive index is linked to the speed of light in the material, so it may seem that, for a material to have negative refractive index, light would have to travel backwards in the material - it doesn't, of course!
	www.geocities.com /mathfair2002/mpjournal/mp1/fibo8.htm (561 words)

	Refractive index Article, Refractiveindex Information (Site not responding. Last check: 2007-10-15)
		If the refractive indices of two materials are known for a given frequency, then one can compute the angle by which radiationof that frequency will be refracted as it moves from the first into the secondmaterial from Snell's law.
		Sometimes the refractive index is defined as a complex number, withthe imaginary part of the number representing the absorption of the material.
		If the index varies quadraticallywith the field (linearly with the intensity), it is called the optical Kerreffect and causes phenomena such as self-focusing and self phase modulation.
	www.anoca.org /velocity/material/refractive_index.html (837 words)

	Physics Today June 2004- Reversing Light With Negative Refraction
		In the form of a wedge refraction experiment, as depicted in figure 2, Snell's law is also the basis for a direct measurement of a material's refractive index.
		The negative medium thus amplifies the wave and compensates for the decay that occurred in an equal thickness of vacuum.
		Negative refraction is a subject with constant capacity for surprise: Innocent assumptions lead to unexpected and sometimes profound consequences.
	www.physicstoday.org /vol-57/iss-6/p37.html (3923 words)

	Metamaterial - Wikipedia, the free encyclopedia
		A material having either (but not both) ε or μ negative is opaque to electromagnetic radiation (see surface plasmon for more details).
		Although the optical properties of a transparent material are fully specified by the parameters ε and μ, in practice the refractive index N is often used.
		The first Superlens (an optical lens employing negative refraction with vastly improved microscopic resolution) was created and demonstrated in 2005 by Xiang Zhang et al of UC Berkeley, as reported in the April 22 issue of the journal Science [1]
	en.wikipedia.org /wiki/Negative_refractive_index (431 words)

	[No title] (Site not responding. Last check: 2007-10-15)
		Exploring the possible implementation of negative index materials for such applications will require significant enhancements in the properties of existing NIM materials (bandwidth, loss, operational frequency, etc.), as well as improved understanding of the physics of their electromagnetic transport properties.
		One direct consequence of a negative phase advance would be the potential to use this phenomenon to compensate for the positive phase advance of a wave that has propagated through a "right-handed" medium, such as free space.
		Since the negative refractive properties are attributed to a combination of negative permittivity and permeability, expanding the frequency range of operation up into the IR and optical spectrums will require the demonstration of materials that exhibit the appropriate dielectric and magnetic responses at these frequencies.
	www.darpa.mil /baa/baa04-12mod5.htm (1357 words)

	Untitled Document
		The negative angle of refraction behavior associated with the negative index of refraction exhibited by DNG metamaterials is demonstrated.
		For the periodic structure with zero averaged refractive index, we demonstrate a number of unique properties of the beam transmission observed in strong beam modification and reshaping.
		Pulse broadening of the signal tails is associated with both dispersion and a larger negative index of refraction seen by the associated wave components.
	physics.ucsd.edu /~drs/LHM_pubs_others_2003.htm (6300 words)

	Refractive index (Site not responding. Last check: 2007-10-15)
		For a non-magnetic material, the square of the refractive index is the dielectric constant
		is the phase velocity of radiation of a specific frequency in a specific material, the refractive index is given by
		The refractive index of a material varies with frequency (except in vacuum, where all frequencies travel at the same speed,
	www.sciencedaily.com /encyclopedia/refractive_index (846 words)

	Radome compensation using matched negative index or refraction materials - US Patent 6788273 (Site not responding. Last check: 2007-10-15)
		A compensated radome is provided, comprising an inner layer of a negative index of refraction material, often referred to as a "metamaterial", and an outer layer of a positive index of refraction material.
		In accordance with the present invention, a compensated radome is provided, comprising an inner layer of a negative index of refraction material, often referred to as a "metamaterial", and an outer layer of a positive index of refraction material.
		Further, it is possible to alter the shape of either of the surfaces on the negative index material 124, using spheric or aspheric surfaces to form lensing surfaces, as is well-known in optical materials.
	www.patentstorm.us /patents/6788273.html (3039 words)

	Metamaterials Publications (Site not responding. Last check: 2007-10-15)
		The negative refraction observed corresponds to left-handed electromagnetism that arises due to the dispersion characteristics of waves in a periodic medium.
		While the refraction of the beam is clearly negative, the modulation interference fronts are not normal to the group velocity, and thus exhibit a sideways motion relative to the beam-an effect due to the inherent frequency dispersion associated with the negative index medium.
		The choices of the square root that leads to the index of refraction and the wave impedance in a DNG medium are determined by imposing analyticity in the complex frequency domain, and the corresponding wave properties associated with each choice are presented.
	ceta-p5.mit.edu /metamaterials/papers/papers.html (12951 words)

	[No title]
		In a negative phase velocity medium, the phase velocity is directed opposite to the direction of energy flow (and attenuation).
		But double negativity is not a necessary condition for the phase velocity to be negative (in a passive material).
		The term negative index medium (NIM) should also be avoided, because it is really the phase velocity which is negatively directed.
	www.esm.psu.edu /~axl4/lakhtakia/ALNPV.html (1144 words)

	The reality of negative refraction (May 2003) - Physics World - PhysicsWeb
		This means that refraction at the interface between a positive-index material and a negative-index material would tear the wave apart, leaving no single negatively refracted wave.
		To make sure that the observed beam was due to the inherent negative index of the wedge - as opposed to an artefact associated with the sample being lossy or diffractive - the team used two different wedge samples so that waves would be incident on the metamaterial at two different angles.
		Both cases exhibited negative refraction at angles that were consistent with the sample having a well defined negative index - confirmation of Snell's law for a negative refractive index.
	physicsweb.org /articles/world/16/5/3 (1597 words)

	Radical Lens Theory Repeals Diffraction Limit - March, 2001 (Site not responding. Last check: 2007-10-15)
		Materials with a negative refractive index have an angle of deflection inverse to conventional media with positive refractive indices.
		Conventional lenses deflect incident light at an angle measurable as the refractive index.
		The index of glass is about 1.4, and lens makers compensate for this deflection by curving the surface of the lens to focus light rays at a point beyond the lens.
	www.photonics.com /spectra/tech/XQ/ASP/techid.1044/QX/read.htm (550 words)

	CommsDesign - Unnatural optics create precise photonic lens (Site not responding. Last check: 2007-10-15)
		A negative refractive index, which is not found in nature, would allow scientists to construct new types of microscopes with unprecedented resolution and could allow the creation of novel photonic devices.
		A transmission medium with a negative index of refractions would enable a flat planar lens to focus light to precisions that are smaller than the wavelength of the light itself.
		With the photonically engineered materials, everything is reversed: The field parameters are negative, and the field vectors are described by a corresponding "left-hand rule." In addition, the electromagnetic direction bends away from the normal to the interface between two media, rather than toward the normal, as in Snell's Law.
	www.commsdesign.com /story/OEG20020826S0041 (1562 words)

	Negative Refraction Confirmed - June, 2003 (Site not responding. Last check: 2007-10-15)
		The latest salvo in the battle over negative refractive index materials has been fired, and it has proponents of their existence declaring a victory.
		Nearly 40 years ago, V.G. Veselago posited that materials with a negative dielectric constant and permeability would have a negative refractive index, refracting an incident ray by the same magnitude but in the opposite direction from the normal line as a typical material.
		Houck noted that the material was rather lossy, attributable in part to the presence of a thin carbon film left on the surfaces by the high-power computer-controlled laser cutter that the researchers use to fabricate the arrays.
	www.photonics.com /spectra/research/XQ/ASP/preaid.121/QX/read.htm (718 words)

	Untitled Document
		In the late 1960s, V.G. Veselago proposed that materials with simultaneously negative permittivity and permeability are physically permissible and possess a negative index of refraction [1].
		His conceptual exploration of this phenomenon revealed that, through negative refraction, planar slabs of such media would cause light or electromagnetic radiation to focus in on itself, as depicted in Figure 1.
		The refractive indices of the RHM and LHM are +1.2 and -2.4, respectively.
	www.waves.utoronto.ca /prof/gelefth/metamaterials.html (926 words)

	NIM
		Exciting results inlcuding negative refraction by a photonic crystal and imaging by a flat lens have been observed in "our three dimensional approach": experiment, theory and simulations.
		Artificial materials with negative refractive index are called left handed materials becaue of the unusual electromagnetic wave propagation in them.
		However, negative index of refraction allows a flat slab of a material to behave as a lens and focus electromagnetic waves as well as produce a real 3-D image.
	sagar.physics.neu.edu /lhm2003/NIM.html (669 words)

	News - June-July 2004
		In theory, however, in a left-handed material, the direction of radiation changes at the surface of a material with a negative index of refraction in such a way as to form a perfect focus on the other side of the solid plate.
		The approach uses the well-known change in refractive index that occurs in silicon as the density of free carrier electrons or holes varies.
		This charge is sufficient to slightly change the index of refraction and shift the phase of the transmitted light.
	www.tipmagazine.com /tip/INPHFA/vol-10/iss-3/p10.html (2082 words)

	Alexander Moroz Home Page (Site not responding. Last check: 2007-10-15)
		Various subjects of theoretical physics, including general scattering theory, the numerical solution of electromagnetic scattering problems, negative refractive index metamaterials, subwavelength nanoguides, surface plasmons, optical imaging of biotissues, quantum optics, light-matter interactions, theory of optical tweezers, and physics of photonic band-gap structures, or, photonic crystals.
		The resulting negative refractive index structure is a truly subwavelength structure with wavelength-to-structure ratio as high as 14:1, which appears to be almost by 50% higher than it has been achieved so far using split ring resonators and wires.
		Refractive index of SiO2 is taken to be 1.45, that of water 1.33, and that of X you can supply yourself.
	www.wave-scattering.com /moroz.html (1175 words)

	Smith and Left-Handed Metamaterials Home Page
		A negative is made of the desired design with a high density printer onto a high quality transparency and placed print side against the PCB.
		The PCB and negative are exposed to UV light in the range of 350-425 nm for 4.5 minutes.
		The mylar layer is then removed by hand and the PBC placed in film developer (sodium carbonate 1% by volume in DI H2O), and scrubbed gently until the unexposed photoresist is removed.
	physics.ucsd.edu /~drs/PRL_2000_details.html (571 words)

	APS - 2005 APS March Meeting PostDeadline - Event - Imaging Potential of a Negative Refractive Index Lens (Site not responding. Last check: 2007-10-15)
		Negative refractive index or left-handed (LH) material has been proposed as a perfect lens, whereby evanescent fields in a lossless LH slab would be amplified.
		Negative permittivity and permeability imply frequency dispersion and, through the Kramers-Kronig relations, loss.
		Expressing the fields in the object plane by plane wave expansion and assuming some degree of loss in the LH slab, the transfer function of the imaging system for each plane wave component can be obtained.
	meetings.aps.org /Meeting/MAR05/Event/24704 (224 words)

	Is There a Perfect Lens? - July, 2002 (Site not responding. Last check: 2007-10-15)
		Instead, they postulate, although phase diffraction may be negative through negative refractive index materials, group refraction will remain positive, distorting any signals and leading to dispersion.
		They concede that an ideal lens made of a negative refractive index material would amplify the evanescent waves -- if it were infinitely thick.
		And in April of that year, a team at the University of California, San Diego, in La Jolla reported an index of refraction of approximately -2.7 for 10.5-GHz microwave radiation in a cellular array of copper split-ring resonators.
	www.photonics.com /spectra/tech/XQ/ASP/techid.1398/QX/read.htm (331 words)

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