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New research field promises radical advances in optical technologies
WEST LAFAYETTE, Ind. - A new research field called transformation
optics may usher in a host of radical advances including a cloak of
invisibility and ultra-powerful microscopes and computers by
harnessing nanotechnology and "metamaterials."
The field, which applies mathematical principles similar to those in
Einstein's theory of general relativity, will be described in an
article to be published Friday (Oct. 17) in the journal Science. The
article will appear in the magazine's Perspectives section and was
written by Vladimir Shalaev, Purdue's Robert and Anne Burnett
Professor of Electrical and Computer Engineering.
The list of possible breakthroughs includes a cloak of invisibility;
computers and consumer electronics that use light instead of
electronic signals to process information; a "planar hyperlens" that
could make optical microscopes 10 times more powerful and able to see
objects as small as DNA; advanced sensors; and more efficient solar
collectors.
"Transformation optics is a new way of manipulating and controlling
light at all distances, from the macro- to the nanoscale, and it
represents a new paradigm for the science of light," Shalaev said.
"Although there were early works that helped to develop the basis for
transformation optics, the field was only recently established thanks
in part to papers by Sir John Pendry at the Imperial College, London,
and Ulf Leonhardt at the University of St. Andrews in Scotland and
their co-workers."
Current optical technologies are limited because, for the efficient
control of light, components cannot be smaller than the size of the
wavelengths of light. Transformation optics sidesteps this limitation
using a new class of materials, or metamaterials, which are able to
guide and control light on all scales, including the scale of
nanometers, or billionths of a meter.
"The whole idea behind metamaterials is to create materials designed
and engineered out of artificial atoms, meta-atoms, which are smaller
than the wavelengths of light itself," Shalaev said. "One of the most
exciting applications is an electromagnetic cloak that could bend
light around itself, similar to the flow of water around a stone,
making invisible both the cloak and an object hidden inside."
Shalaev and researchers from his group - doctoral students Wenshan Cai
and Uday K. Chettiar and principal research scientist Alexander V.
Kildishev - in 2007 took a step toward creating an optical cloaking
device in the visible range of the spectrum. Their theoretical design
uses an array of tiny needles radiating outward from a central spoke,
resembling a round hairbrush, and would bend light around the object
being cloaked.
The mathematical equations for transformation optics are similar to
the mathematics behind Einstein's theory of general relativity, which
describes how gravity warps space and time, Shalaev said.
"Whereas relativity demonstrates the curved nature of space and time,
we are able to curve space for light, and we can design and engineer
tiny devices to do this," he said. "In addition to curving light
around an object to render it invisible, you could do just the
opposite - concentrate light in an area, which might be used for
collecting sunlight in solar energy applications. So, general
relativity may find practical use in a number of novel optical devices
based on transformation optics."
The metamaterials also may enable engineers to overcome obstacles now
confronting the semiconductor industry: It is becoming increasingly
difficult to make faster computer chips because the technology is
reaching its limits. But computers using light instead of electronic
signals to process information would be thousands of times faster than
conventional computers. Such "photonic" computers would contain
special transistor-size optical elements made from metamaterials.
Transformation optics also could enable engineers to design and build
a "planar magnifying hyperlens" that would drastically improve the
power and resolution of light microscopes.
"The hyperlens is probably the most exciting and promising
metamaterial application to date," Shalaev said. "The first hyperlens,
proposed independently by Evgenii Narimanov at Princeton and Nader
Engheta at the University of Pennsylvania and their co-workers, was
cylindrical in shape. Transformation optics, however, enables a
hyperlens in a planar form, which is important because you could just
simply add this flat hyperlens to conventional microscopes and see
things 10 times smaller than now possible. You could focus down to the
nanoscale, much smaller than the wavelength of light, to actually see
molecules like DNA, viruses and other objects that are now simply too
small to see."
The hyperlens theoretically would compensate for the loss of a portion
of the light transmitting fine details of an image as it passes
through a lens. Lenses and imaging systems could be improved if this
lost light, which scientists call "evanescent light," could be
restored. Such a hyperlens would both magnify an image and convert
this evanescent light so that it does not weaken with distance but
continues to propagate.
Meta in Greek means beyond, so the term metamaterial means to create
something that doesn't exist in nature.
Unlike natural materials, metamaterials are able to reduce the "index
of refraction" to less than one or less than zero. Refraction occurs
as electromagnetic waves, including light, bend when passing from one
material into another. It causes the bent-stick-in-water effect, which
occurs when a stick placed in a glass of water appears bent when
viewed from the outside. Each material has its own refraction index,
which describes how much light will bend in that particular material
and defines how much the speed of light slows down while passing
through a material.
Natural materials typically have refractive indices greater than one.
Metamaterials, however, can make the index of refraction vary from
zero to one, which possibly will enable cloaking as well as other
advances, Shalaev said.
He estimated that researchers may be building prototypes using
transformation optics, such as the first planar hyperlenses, within
five years.
###
Various research groups around the world are working in transformation
optics. The U.S. Office of Naval Research and Department of Defense
are creating a new multidisciplinary university research initiative,
or MURI, to fund work in the field. MURIs are collaborative efforts
among researchers at several universities, but the participants have
not yet been selected.
Shalaev's research is based at the Birck Nanotechnology Center at
Purdue's Discovery Park. The research is funded by the U.S. Army
Research Office.
Writer: Emil Venere, (765) 494-4709, venere@purdue.edu
Source: Vladimir Shalaev, (765) 494-9855, shalaev@ecn.purdue.edu
Related Web site:
Vladimir Shalaev: https://engineering.purdue.edu/ECE/People/profile?resource_id=3322
IMAGE CAPTION:
These are graphical representations of numerical simulations depicting
four potential applications of a new field called transformation
optics. Clockwise from top left are: a design for optical cloaking; a
light "concentrator" for sensors and solar collectors; a "planar
hyperlens" and "impedence-matched hyperlens" for applications
including microscopes. (Courtesy of the journal Science)
A publication-quality image is available at
http://news.uns.purdue.edu/images/+2008/transformation-optics.jpg
Note to Journalists: A copy of the research paper is available by
contacting the Science Press Package team at (202) 326-6440,
scipak@aaas.org
http://www.eurekalert.org/pub_releases/2008-10/pu-nrf101408.php
WEST LAFAYETTE, Ind. - A new research field called transformation
optics may usher in a host of radical advances including a cloak of
invisibility and ultra-powerful microscopes and computers by
harnessing nanotechnology and "metamaterials."
The field, which applies mathematical principles similar to those in
Einstein's theory of general relativity, will be described in an
article to be published Friday (Oct. 17) in the journal Science. The
article will appear in the magazine's Perspectives section and was
written by Vladimir Shalaev, Purdue's Robert and Anne Burnett
Professor of Electrical and Computer Engineering.
The list of possible breakthroughs includes a cloak of invisibility;
computers and consumer electronics that use light instead of
electronic signals to process information; a "planar hyperlens" that
could make optical microscopes 10 times more powerful and able to see
objects as small as DNA; advanced sensors; and more efficient solar
collectors.
"Transformation optics is a new way of manipulating and controlling
light at all distances, from the macro- to the nanoscale, and it
represents a new paradigm for the science of light," Shalaev said.
"Although there were early works that helped to develop the basis for
transformation optics, the field was only recently established thanks
in part to papers by Sir John Pendry at the Imperial College, London,
and Ulf Leonhardt at the University of St. Andrews in Scotland and
their co-workers."
Current optical technologies are limited because, for the efficient
control of light, components cannot be smaller than the size of the
wavelengths of light. Transformation optics sidesteps this limitation
using a new class of materials, or metamaterials, which are able to
guide and control light on all scales, including the scale of
nanometers, or billionths of a meter.
"The whole idea behind metamaterials is to create materials designed
and engineered out of artificial atoms, meta-atoms, which are smaller
than the wavelengths of light itself," Shalaev said. "One of the most
exciting applications is an electromagnetic cloak that could bend
light around itself, similar to the flow of water around a stone,
making invisible both the cloak and an object hidden inside."
Shalaev and researchers from his group - doctoral students Wenshan Cai
and Uday K. Chettiar and principal research scientist Alexander V.
Kildishev - in 2007 took a step toward creating an optical cloaking
device in the visible range of the spectrum. Their theoretical design
uses an array of tiny needles radiating outward from a central spoke,
resembling a round hairbrush, and would bend light around the object
being cloaked.
The mathematical equations for transformation optics are similar to
the mathematics behind Einstein's theory of general relativity, which
describes how gravity warps space and time, Shalaev said.
"Whereas relativity demonstrates the curved nature of space and time,
we are able to curve space for light, and we can design and engineer
tiny devices to do this," he said. "In addition to curving light
around an object to render it invisible, you could do just the
opposite - concentrate light in an area, which might be used for
collecting sunlight in solar energy applications. So, general
relativity may find practical use in a number of novel optical devices
based on transformation optics."
The metamaterials also may enable engineers to overcome obstacles now
confronting the semiconductor industry: It is becoming increasingly
difficult to make faster computer chips because the technology is
reaching its limits. But computers using light instead of electronic
signals to process information would be thousands of times faster than
conventional computers. Such "photonic" computers would contain
special transistor-size optical elements made from metamaterials.
Transformation optics also could enable engineers to design and build
a "planar magnifying hyperlens" that would drastically improve the
power and resolution of light microscopes.
"The hyperlens is probably the most exciting and promising
metamaterial application to date," Shalaev said. "The first hyperlens,
proposed independently by Evgenii Narimanov at Princeton and Nader
Engheta at the University of Pennsylvania and their co-workers, was
cylindrical in shape. Transformation optics, however, enables a
hyperlens in a planar form, which is important because you could just
simply add this flat hyperlens to conventional microscopes and see
things 10 times smaller than now possible. You could focus down to the
nanoscale, much smaller than the wavelength of light, to actually see
molecules like DNA, viruses and other objects that are now simply too
small to see."
The hyperlens theoretically would compensate for the loss of a portion
of the light transmitting fine details of an image as it passes
through a lens. Lenses and imaging systems could be improved if this
lost light, which scientists call "evanescent light," could be
restored. Such a hyperlens would both magnify an image and convert
this evanescent light so that it does not weaken with distance but
continues to propagate.
Meta in Greek means beyond, so the term metamaterial means to create
something that doesn't exist in nature.
Unlike natural materials, metamaterials are able to reduce the "index
of refraction" to less than one or less than zero. Refraction occurs
as electromagnetic waves, including light, bend when passing from one
material into another. It causes the bent-stick-in-water effect, which
occurs when a stick placed in a glass of water appears bent when
viewed from the outside. Each material has its own refraction index,
which describes how much light will bend in that particular material
and defines how much the speed of light slows down while passing
through a material.
Natural materials typically have refractive indices greater than one.
Metamaterials, however, can make the index of refraction vary from
zero to one, which possibly will enable cloaking as well as other
advances, Shalaev said.
He estimated that researchers may be building prototypes using
transformation optics, such as the first planar hyperlenses, within
five years.
###
Various research groups around the world are working in transformation
optics. The U.S. Office of Naval Research and Department of Defense
are creating a new multidisciplinary university research initiative,
or MURI, to fund work in the field. MURIs are collaborative efforts
among researchers at several universities, but the participants have
not yet been selected.
Shalaev's research is based at the Birck Nanotechnology Center at
Purdue's Discovery Park. The research is funded by the U.S. Army
Research Office.
Writer: Emil Venere, (765) 494-4709, venere@purdue.edu
Source: Vladimir Shalaev, (765) 494-9855, shalaev@ecn.purdue.edu
Related Web site:
Vladimir Shalaev: https://engineering.purdue.edu/ECE/People/profile?resource_id=3322
IMAGE CAPTION:
These are graphical representations of numerical simulations depicting
four potential applications of a new field called transformation
optics. Clockwise from top left are: a design for optical cloaking; a
light "concentrator" for sensors and solar collectors; a "planar
hyperlens" and "impedence-matched hyperlens" for applications
including microscopes. (Courtesy of the journal Science)
A publication-quality image is available at
http://news.uns.purdue.edu/images/+2008/transformation-optics.jpg
Note to Journalists: A copy of the research paper is available by
contacting the Science Press Package team at (202) 326-6440,
scipak@aaas.org
http://www.eurekalert.org/pub_releases/2008-10/pu-nrf101408.php