New Hologram Technology Created With Tiny Nanoantennas
Researchers have created
tiny holograms using a "metasurface" capable of the ultra-efficient
control of light, representing a potential new technology for advanced sensors,
high-resolution displays and information processing.
The metasurface,
thousands of V-shaped nanoantennas formed into an ultrathin gold foil, could
make possible "planar photonics" devices and optical switches small
enough to be integrated into computer chips for information processing, sensing
and telecommunications, said Alexander Kildishev, associate research professor
of electrical and computer engineering at Purdue University.
Laser light shines
through the nanoantennas, creating the hologram 10 microns above the
metasurface. To demonstrate the technology, researchers created a hologram of
the word PURDUE smaller than 100 microns wide, or roughly the width of a human
hair.
"If we can shape characters,
we can shape different types of light beams for sensing or recording, or, for
example, pixels for 3-D displays. Another potential application is the
transmission and processing of data inside chips for information
technology," Kildishev said. "The smallest features -- the strokes of
the letters -- displayed in our experiment are only 1 micron wide. This is a
quite remarkable spatial resolution."
Findings are detailed in
a research paper appearing on Friday (Nov. 15) in the journal Nature
Communications.
Metasurfaces could make
it possible to use single photons -- the particles that make up light -- for
switching and routing in future computers. While using photons would
dramatically speed up computers and telecommunications, conventional photonic devices
cannot be miniaturized because the wavelength of light is too large to fit in
tiny components needed for integrated circuits.
Nanostructured
metamaterials, however, are making it possible to reduce the wavelength of
light, allowing the creation of new types of nanophotonic devices, said
Vladimir M. Shalaev, scientific director of nanophotonics at Purdue's Birck
Nanotechnology Center and a distinguished professor of electrical and computer
engineering.
"The most important
thing is that we can do this with a very thin layer, only 30 nanometers, and
this is unprecedented," Shalaev said. "This means you can start to
embed it in electronics, to marry it with electronics."
The layer is about
1/23rd the width of the wavelength of light used to create the holograms.
The Nature
Communications article was co-authored by former Purdue doctoral
student Xingjie Ni, who is now a postdoctoral researcher at the University of
California, Berkeley; Kildishev; and Shalaev.
Under development for
about 15 years, metamaterials owe their unusual potential to precision design
on the scale of nanometers. Optical nanophotonic circuits might harness clouds
of electrons called "surface plasmons" to manipulate and control the
routing of light in devices too tiny for conventional lasers.
The researchers have
shown how to control the intensity and phase, or timing, of laser light as it
passes through the nanoantennas. Each antenna has its own "phase
delay" -- how much light is slowed as it passes through the structure.
Controlling the intensity and phase is essential for creating working devices
and can be achieved by altering the V-shaped antennas.
The work is partially
supported by U.S. Air Force Office of Scientific Research, Army research
Office, and the National Science Foundation. Purdue has filed a provisional
patent application on the concept.