Navigation Links
New device hides, on cue, from infrared cameras
Date:11/26/2012

Cambridge, Mass. - November 26, 2012 - Now you see it, now you don't.

A new device invented at the Harvard School of Engineering and Applied Sciences (SEAS) can absorb 99.75% of infrared light that shines on it. When activated, it appears black to infrared cameras.

Composed of just a 180-nanometer-thick layer of vanadium dioxide (VO2) on top of a sheet of sapphire, the device reacts to temperature changes by reflecting dramatically more or less infrared light.

Announced today in the journal Applied Physics Letters, and featured on its cover, this perfect absorber is ultrathin, tunable, and exceptionally well suited for use in a range of infrared optical devices.

Perfect absorbers have been created many times before, but not with such versatile properties. In a Fabry-Prot cavity, for instance, two mirrors sandwich an absorbing material, and light simply reflects light back and forth until it's mostly all gone. Other devices incorporate surfaces with nanoscale metallic patterns that trap and eventually absorb the light.

"Our structure uses a highly unusual approach, with better results," says principal investigator Federico Capasso, Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering at SEAS. "We exploit a kind of naturally disordered metamaterial, along with thin-film interference effects, to achieve one of the highest absorption rates we've ever seen. Yet our perfect absorber is structurally simpler than anything tried before, which is important for many device applications."

With collaborators at Harvard and at the University of California, San Diego, Capasso's research group took advantage of surprising properties in both of the materials they used.

Vanadium dioxide is normally an insulating material, meaning that it does not conduct electricity well. Take it from room temperature up to about 68 degrees Celsius, however, and it undergoes a dramatic transition. The crystal quickly rearranges itself as the temperature approaches a critical value. Metallic islands appear as specks, scattered throughout the material, with more and more appearing until it has become uniformly metallic.

"Right near this insulator-to-metal transition, you have a very interesting mixed medium, made up of both insulating and metallic phases," says coauthor Shriram Ramanathan, Associate Professor of Materials Science at SEAS, who synthesized the thin film. "It's a very complex and rich microstructure in terms of its electronic properties, and it has very unusual optical properties."

Those properties, when manipulated correctly, happen to be ideal for infrared absorption.

Meanwhile, the underlying sapphire substrate has a secret of its own. Usually transparent, its crystal structure actually makes it opaque and reflective, like a metal, to a narrow subset of infrared wavelengths.

The result is a combination of materials that internally reflects and devours incident infrared light.

"Both of these materials have lots of optical losses, and we've demonstrated that when light reflects between lossy materials, instead of transparent or highly reflective ones, you get strange interface reflections," explains lead author Mikhail Kats, a graduate student at SEAS. "When you combine all of those resulting waves, you can coax them to destructively interfere and completely cancel out. The net effect is that a film one hundred times thinner than the wavelength of the incident light can create perfect absorption."

The challenge for Capasso, Ramanathan, Kats, and their colleagues was not only to understand this behavior, but also to learn how to fabricate pure enough samples of the vanadium dioxide.

"Vanadium oxide can exist in many oxidation states, and only if you have VO2 does it go through a metal-insulator transition close to room temperature," Ramanathan explains. "We have developed several techniques in our lab to allow exquisite compositional and structural control, almost at the atomic scale, to grow such complex films. The resulting phase purity allows us to see these remarkable properties, which otherwise would be very difficult to observe."

Because the device can be easily switched between its absorbent and non-absorbent states, the possible applications are quite wide ranging and include bolometers (thermal imaging devices) with tunable absorption, spectroscopy devices, tunable filters, thermal emitters, radiation detectors, and equipment for energy harvesting.

"An ideal bolometer design needs to absorb all of the infrared light that falls on it, turning it to heat, and correspondingly its resistance should change a lot per degree change in temperature," notes Kats. "In principle, our new perfect absorber could be used to make incredibly sensitive thermal cameras."

Harvard's Office of Technology Development has filed patent applications on the novel invention and is actively pursuing licensing and commercialization opportunities.


'/>"/>

Contact: Caroline Perry
cperry@seas.harvard.edu
617-496-1351
Harvard University
Source:Eurekalert  

Related biology technology :

1. New portable device enables RNA detection from ultra-small sample in only 20 minutes
2. All Market Research Predicts the Global Ophthalmology Devices Market Will Reach $18,286.4 Million in 2018
3. New UCLA Engineering research center to revolutionize nanoscale electromagnetic devices
4. Center will create self-powered health monitoring devices
5. Surgical Equipment Market (Surgical Sutures, Surgical Hand Instruments And Electrosurgical Devices) - Global Forecast, Market Share, Size, Growth And Industry Analysis (2010-2017): Twease.org
6. Global Endoscopy Devices Market is Expected to Reach USD 10.8 Billion in 2017: Transparency Market Research
7. MarketsandMarkets: Global Spine Surgery Devices Market Worth $14.8 Billion by 2017
8. Neonatal and Preterm Infants Enteral Feeding Devices Market is Expected to Reach USD 2.62 Billion Globally by 2018: Transparency Market Research
9. Former FDA Inspectors Train Medical Device, Pharmaceutical Companies How to Prepare for FDA Inspections of Their Quality Systems
10. UK research paves way to a scalable device for quantum information processing
11. UMass Amherst, Harvard experts say better systems needed for medical device cybersecurity
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
New device hides, on cue, from infrared cameras
(Date:2/11/2016)... --  BioInformant announces the February 2016 release of ... Tools, and Technologies – Market Size, Segments, Trends, and ... The first and only market research ... has more than a decade of historical information on ... cell type. This powerful 175 page global strategic report ...
(Date:2/10/2016)... , Febr. 10, 2016 /PRNewswire/ - BioAmber Inc. (NYSE: ... to announce that Mitsui & Co. Ltd., its partner ... acid plant, is investing an additional CDN$25 million in ... its stake from 30% to 40%.  Mitsui will also ... acid produced in Sarnia , providing ...
(Date:2/10/2016)... , Feb.10, 2016 ASAE is introducing a ... Management Companies (AMC) the option of joining or renewing ... fee determined by staff size, every employee in any ... ASAE and reap all available member benefits.   ... new organizational membership options will allow organizations of any ...
(Date:2/10/2016)... BOSTON , Feb. 10, 2016  Matchbook, ... sourcing for fast growing biotech companies, announced today ... Senior Procurement Strategic Advisor. Jim brings nearly 25 ... sourcing and procurement, having spent nearly two decades ... Supply Chain/Logistics and Procurement at Genzyme and, most ...
Breaking Biology Technology:
(Date:2/2/2016)... RESTON, Va. , Feb. 2, 2016 /PRNewswire/ ... contract award from the U.S. Army Research Office ... extend the range and sensitivity of the company,s ... DoD,s Past Accounting Mission and, more generally, defense-related ... its DNA phenotyping capabilities (predicting appearance and ancestry ...
(Date:1/28/2016)... Jan. 28, 2016 Synaptics (NASDAQ: SYNA ), a ... its second quarter ended December 31, 2015. ... of fiscal 2016 increased 2 percent compared to the comparable quarter ... of fiscal 2016 was $35.0 million, or $0.93 per diluted share. ... income for the first quarter of fiscal 2016 grew 9 percent ...
(Date:1/22/2016)... , Jan. 22, 2016 ... the addition of the "Global Biometrics ... to their offering. --> ... the "Global Biometrics Market in Retail ... --> Research and Markets ...
Breaking Biology News(10 mins):