Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New superlens opens door to nanoscale optical imaging, high-density optoelectronics

22.04.2005


At left (A) is an image of an array of nanowires 60 nanometers wide created with the silver superlens. The center distance between each nanowire is 120 nanometers. To the right (B) is an image of the same nanowires. In this image, created without the superlens, the individual nanowires are not distinct. The scale bar on both images is 1 micrometer. (Image by Cheng Sun, UC Berkeley)


Shown is a drawing of nano-scale imaging using a silver superlens that achieves a resolution beyond the optical diffraction limit. The red line indicates the enhancement of "evanescent" waves as they pass through the superlens. (Image by Cheng Sun, UC Berkeley)


A group of scientists at the University of California, Berkeley, is giving new relevance to the term "sharper image" by creating a superlens that can overcome a limitation in physics that has historically constrained the resolution of optical images.

Using a thin film of silver as the lens and ultraviolet (UV) light, the researchers recorded the images of an array of nanowires and the word "NANO" onto an organic polymer at a resolution of about 60 nanometers. In comparison, current optical microscopes can only make out details down to one-tenth the diameter of a red blood cell, or about 400 nanometers.

The breakthrough, reported in the April 22 issue of the journal Science, opens the door to dramatic technological advances in nanoengineering that could eventually lead to DVDs that store the entire contents of the Library of Congress, and computer processors that can quickly search through such a huge volume of data, the researchers said.



"The field of optics is involved in much of today’s technology, including imaging and photolithography, which is used to make semiconductors and integrated circuits," said Xiang Zhang, UC Berkeley associate professor of mechanical engineering and principal investigator of the study. "Our work has a far reaching impact on the development of detailed biomedical imaging, higher density electronic circuitry and ever-faster fiber optic communications."

Nicholas Fang, one of Zhang’s former Ph.D. students and lead author of the paper, said a nearer term application would be the development of medical imaging devices that could reveal never-before-seen details with optical microscopy.

With current optical microscopes, scientists can only make out relatively large structures within a cell, such as its nucleus and mitochondria. With a superlens, optical microscopes could one day reveal the movements of individual proteins traveling along the microtubules that make up a cell’s skeleton, the researchers said.

Scanning electron and atomic force microscopes are now used to capture detail down to a few nanometers. However, such microscopes create images by scanning objects point by point, which means they are typically limited to non-living samples, and image capture times can take up to several minutes.

"Optical microscopes can capture an entire frame with a single snapshot in a fraction of a second," said Fang, who is now an assistant professor of mechanical engineering at the University of Illinois at Urbana-Champaign. "That opens up nanoscale imaging to living materials, which can help biologists better understand cell structure and function in real time, and ultimately help in the development of new drugs to treat human diseases."

The study is the latest entry in a hotly debated topic among physicists and engineers surrounding the creation of a lens that can break the so-called diffraction limit of optics through negative refraction.

Conventional lenses, whether manmade or natural, create images by capturing the propagating light waves all objects emit and then bending them. The angle of the bend is determined by the index of refraction and has always been positive.

Yet objects also emit "evanescent" waves that carry a great deal of detail but are far more elusive. Such evanescent waves decay exponentially and thus never make it to the image plane, an optics threshold known as the diffraction limit. Breaking this diffraction limit and capturing evanescent waves are critical to the creation of a 100-percent perfect representation of an object, considered the Holy Grail in optics.

In 2000, British physicist John Pendry theorized that a material capable of a negative index of refraction could capture and "refocus" evanescent waves into a perfect image. Pendry’s proposed "perfect lens" theory came more than 30 years after Russian physicist Victor Veselago first conceived of a negative refraction material that could reverse known optical phenomena.

These theories are based on the fact that when electromagnetic waves of light reach the surface of a negative refraction lens, they excite a collective movement of surface waves, such as electron oscillations, also known as surface plasmons. That results in an enhancement of the evanescent waves and is different from the way light typically behaves when it reaches a conventional lens.

Various negative refraction experiments were later conducted by researchers at UC San Diego, Boeing and Northeastern University, but they were limited to microwave beams.

In 2003, Zhang’s group was the first to confirm that optical evanescent waves are enhanced as they pass through a silver superlens in carefully designed conditions.

But it wasn’t until this latest experiment by Zhang’s group that optical imaging with a superlens was demonstrated. Zhang and his research team used UV light at a 365-nanometer wavelength in the new experiments, so the image created actually has more detail than is possible with beams in the microwave range.

The array of nanowires imaged measured 40 nanometers wide and the word NANO was about 60 nanometers wide. The objects, embedded onto a layer of chrome, were placed before the superlens, which was a layer of silver that was about 35 nanometers thick. The researchers recorded the image onto a photoresist, a polymer coating on the other side of the superlens that becomes insoluble when exposed to UV light.

"Our work provides a new imaging method that can beat the optical diffraction limit and that has tremendous potential to revolutionize a wide range of technologies," said Zhang. "The key to the superlens is its ability to significantly enhance and recover the evanescent waves that carry information at very small scales. This enables imaging well below the diffraction limit."

Notably, no lens is yet able to completely reconstitute all the evanescent waves emitted by an object, so the goal of a 100-percent perfect image is still out there. However, many scientists believe that a true perfect lens is not possible because there will always be some energy absorption loss as the waves pass through any known material.

"We did not create a perfect image in our experiment," said Fang. "But it’s clear that our image is dramatically better than the one created without the silver superlens."

In the long run, this line of research could lead to even higher resolution imaging for distant objects, the researchers said. This includes more detailed views of other planets as well as of human movement through surveillance satellites.

Sarah Yang | EurekAlert!
Further information:
http://www.berkeley.edu

More articles from Physics and Astronomy:

nachricht Climate cycles may explain how running water carved Mars' surface features
02.12.2016 | Penn State

nachricht What do Netflix, Google and planetary systems have in common?
02.12.2016 | University of Toronto

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

Im Focus: Fraunhofer ISE Develops Highly Compact, High Frequency DC/DC Converter for Aviation

The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

UTSA study describes new minimally invasive device to treat cancer and other illnesses

02.12.2016 | Medical Engineering

Plasma-zapping process could yield trans fat-free soybean oil product

02.12.2016 | Agricultural and Forestry Science

What do Netflix, Google and planetary systems have in common?

02.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>