Featured Research

from universities, journals, and other organizations

Metamaterials may advance with new femtosecond laser technique

Date:
March 8, 2012
Source:
Harvard School of Engineering and Applied Sciences
Summary:
"Lucky" combination of chemicals and laser pulses enables high-resolution, 3D patterning for futuristic optical materials

A new laser fabrication technique developed at Harvard allows for the creation of precisely arranged silver nanoparticles that are disconnected in 3D and supported by a polymer matrix. The new technique may prove critical in the development of metamaterials.
Credit: Image courtesy of Kevin Vora

Researchers in applied physics have cleared an important hurdle in the development of advanced materials, called metamaterials, that bend light in unusual ways.

Working at a scale applicable to infrared light, the Harvard team has used extremely short and powerful laser pulses to create three-dimensional patterns of tiny silver dots within a material. Those suspended metal dots are essential for building futuristic devices like invisibility cloaks.

The new fabrication process, described in the journal Applied Physics Letters, advances nanoscale metal lithography into three dimensions -- and does it at a resolution high enough to be practical for metamaterials.

"If you want a bulk metamaterial for visible and infrared light, you need to embed particles of silver or gold inside a dielectric, and you need to do it in 3D, with high resolution," says lead author Kevin Vora, a graduate student at the Harvard School of Engineering and Applied Sciences (SEAS).

"This work demonstrates that we can create silver dots that are disconnected in x, y, and z," Vora says. "There's no other technique that feasibly allows you to do that. Being able to make patterns of nanostructures in 3D is a very big step towards the goal of making bulk metamaterials."

Vora works in the laboratory of Eric Mazur, Balkanski Professor of Physics and Applied Physics at SEAS. For decades, Mazur has been using a piece of equipment called a femtosecond laser to investigate how very tightly focused, powerful bursts of light can change the electrical, optical, and physical properties of a material.

When a conventional laser shines on a transparent material, the light passes straight through, with slight refraction. The femtosecond laser is special because it emits a burst of photons as bright as the surface of the sun in a flash lasting only 50 quadrillionths (5 10-14) of a second. Instead of shining through the material, that energy gets trapped within it, exciting the electrons within the material and achieving a phenomenon known as nonlinear absorption.

Inside the pocket where that energy is trapped, a chemical reaction can take place, permanently altering the internal structure of the material. The process has previously been exploited for 2D and simple 3D metal nanofabrication.

"Normally, when people use femtosecond lasers in fabrication, they're creating a wood pile structure: something stacked on something else, being supported by something else," explains Mazur.

"If you want to make an array of silver dots, however, they can't float in space."

In the new process, Vora, Mazur, and their colleagues combine silver nitrate, water, and a polymer called PVP into a solution, which they bake onto a glass slide. The solid polymer then contains ions of silver, which are photoreduced by the tightly focused laser pulses to form nanocrystals of silver metal, supported by the polymer matrix.

The need for this particular combination of chemicals, at the right concentrations, was not obvious in prior work. Researchers sometimes combine silver nitrate with water in order to create silver nanostructures, but that process provides no structural support for a 3D pattern. Another process combines silver nitrate, water, PVP, and ethanol, but the samples darken and degrade very quickly by producing silver crystals throughout the polymer.

With ethanol, the reaction happens too quickly and uncontrollably. Mazur's team needed nanoscale crystals, precisely distributed and isolated in 3D.

"It was just a question of removing that reagent, and we got lucky," Vora says. "What was most surprising about it was how simple it is. It was a matter of using less."

SeungYeon Kang, a graduate student at SEAS, and Shobha Shukla, a former postdoctoral fellow, coauthored the paper. The work was supported by the Air Force Office of Scientific Research.


Story Source:

The above story is based on materials provided by Harvard School of Engineering and Applied Sciences. Note: Materials may be edited for content and length.


Journal Reference:

  1. Kevin Vora, SeungYeon Kang, Shobha Shukla, Eric Mazur. Fabrication of disconnected three-dimensional silver nanostructures in a polymer matrix. Applied Physics Letters, 2012; 100 (6): 063120 DOI: 10.1063/1.3684277

Cite This Page:

Harvard School of Engineering and Applied Sciences. "Metamaterials may advance with new femtosecond laser technique." ScienceDaily. ScienceDaily, 8 March 2012. <www.sciencedaily.com/releases/2012/03/120308115745.htm>.
Harvard School of Engineering and Applied Sciences. (2012, March 8). Metamaterials may advance with new femtosecond laser technique. ScienceDaily. Retrieved August 23, 2014 from www.sciencedaily.com/releases/2012/03/120308115745.htm
Harvard School of Engineering and Applied Sciences. "Metamaterials may advance with new femtosecond laser technique." ScienceDaily. www.sciencedaily.com/releases/2012/03/120308115745.htm (accessed August 23, 2014).

Share This




More Matter & Energy News

Saturday, August 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Is It a Plane? No, It's a Hoverbike

Is It a Plane? No, It's a Hoverbike

Reuters - Business Video Online (Aug. 22, 2014) UK-based Malloy Aeronautics is preparing to test a manned quadcopter capable of out-manouvering a helicopter and presenting a new paradigm for aerial vehicles. A 1/3-sized scale model is already gaining popularity with drone enthusiasts around the world, with the full-sized manned model expected to take flight in the near future. Matthew Stock reports. Video provided by Reuters
Powered by NewsLook.com
Coal Gas Boom in China Holds Climate Risks

Coal Gas Boom in China Holds Climate Risks

AP (Aug. 22, 2014) China's energy revolution could do more harm than good for the environment, despite the country's commitment to reducing pollution and curbing its carbon emissions. (Aug. 22) Video provided by AP
Powered by NewsLook.com
Former TSA X-Ray Scanners Easily Tricked To Miss Weapons

Former TSA X-Ray Scanners Easily Tricked To Miss Weapons

Newsy (Aug. 21, 2014) Researchers found the scanners could be duped simply by placing a weapon off to the side of the body or encasing it under a plastic shield. Video provided by Newsy
Powered by NewsLook.com
Flower Power! Dandelions Make Car Tires?

Flower Power! Dandelions Make Car Tires?

Reuters - Business Video Online (Aug. 20, 2014) Forget rolling on rubber, could car drivers soon be traveling on tires made from dandelions? Teams of scientists are racing to breed a type of the yellow flower whose taproot has a milky fluid with tire-grade rubber particles in it. As Joanna Partridge reports, global tire makers are investing millions in research into a new tire source. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins