Nanotechnology Now

Our NanoNews Digest Sponsors
Heifer International



Home > Press > Researchers transform slow emitters into fast light sources

Phosphors are efficient light emitters but they're not optimal for high-speed communications because they turn on and off slowly. Researchers from Brown and Harvard have now found a way to modulate light from phosphor emitters three orders of magnitude faster using phase-change materials (VO2, in this case), which could make phosphors useful in a range of new optoelectronic applications.
CREDIT: Zia Lab / Brown University
Phosphors are efficient light emitters but they're not optimal for high-speed communications because they turn on and off slowly. Researchers from Brown and Harvard have now found a way to modulate light from phosphor emitters three orders of magnitude faster using phase-change materials (VO2, in this case), which could make phosphors useful in a range of new optoelectronic applications.

CREDIT: Zia Lab / Brown University

Abstract:
Researchers from Brown University, in collaboration with colleagues from Harvard, have developed a new way to control light from phosphorescent emitters at very high speeds. The technique provides a new approach to modulation that could be useful in all kinds of silicon-based nanoscale devices, including computer chips and other optoelectronic components.

Researchers transform slow emitters into fast light sources

Providence, RI | Posted on October 22nd, 2015

"Our results demonstrate relatively fast modulation from fundamentally slow phosphorescent light emitters," said Rashid Zia, associate professor of engineering and physics at Brown and senior author of a new paper describing the work. "We think this could help make phosphors useful in a variety of new systems and settings."

The paper is published today in Nature Communications.

Phosphors are common light emitters used in light bulbs, LEDs and elsewhere. They are extremely efficient because much of the energy pumped into them is converted to light as opposed to heat. But they have a slow optical lifetime, meaning it takes a relatively long time for them to return to the ground state after being excited. As a result, phosphors can't be turned on and off very quickly. Glow-in-the-dark toys, for example, take advantage of this property.

That property is bad, however, for optical modulation, a process that often involves flipping the light on and off to encode information. Because of their slow lifetimes, phosphors have traditionally been a non-starter for applications that require high-speed modulation.

But in this latest work, Zia and collaborators, including researchers from Shriram Ramanathan's group at Harvard University, took a different approach to modulation.

"Instead of changing how much light is coming out, which can only be done slowly in phosphor emitters, we came up with a system that changes another quality of that light, namely the color or spectrum of light emission, by rapidly changing the environment around the emitter," Zia said.

The work was led by Sebastien Cueff, a postdoctoral researcher in Zia's lab. Cueff started with an emitter made of erbium ions, an important phosphor that is widely used in fiber-optic telecommunication networks. He combined that with a material called vanadium dioxide (VO2). VO2 is a phase-change material that, when pumped with energy, changes very quickly from a transparent insulating state to a reflective metallic state. This change in reflectivity, in turn, switches how nearby erbium ions emit light. As the VO2 changes phase, the erbium emissions go from being generated mostly by magnetic dipole transitions (the rotational torque push and pull of magnetic forces), to being generated mostly by electric dipole transitions (the linear push and pull of electric forces). Those two emission pathways have distinct spectra, and the modulation back and forth between the two can be used as a means to encode information.

The researchers showed that this direct modulation of light emission could be done as quickly as the VO2 phase could be changed, which is much faster than the speed at which erbium can be turned on and off. The test system used in these initial experiments showed that the system could be switched three orders of magnitude faster than the optical lifetime of erbium.

"Phosphorescent emitters have been considered impractical for high speed applications because of their intrinsically long lifetimes," Zia said. "Our results provide a simple way to circumvent this limitation and modulate their emission at high speeds."

And that could enable the use of phosphors in new applications. One example could be optical communications networks on computer chips.

Prototype on-chip networks have used semiconductor lasers as light emitters. They can modulate very quickly, but they have downsides. Semiconductors can't be grown directly on a silicon chip, so fabrication can be difficult. Using indirect means of modulation -- interferometers, for example -- makes for bulky systems that take up a lot of real estate on a chip. What's more, semiconductor lasers are not particularly efficient. They produce a lot of heat along with light, which is a problem on a silicon chip.

Erbium and other phosphors, on the other hand, can be deposited directly on silicon, making fabrication easier. And phosphors are highly efficient, so heat is less of a concern. There's still more work to be done to get such a system up to a speed that would be useful on a chip, but Zia and his colleagues think it's possible.

In this initial experiment, the researchers used a laser to zap the VO2 and cause it to change phase. A faster means of changing the VO2 phase -- perhaps using electricity instead of a laser -- could make the system much faster still.

Zia and his group plan to continue to refine the technique, but they describe this first set of experiments as an important proof of concept. "We ... hope that the device and concept presented here will engage both academic and industrial researchers working on optoelectronics and nanophotonics," the researchers write.

###

Other authors on the paper were Dongfang Li (Brown), You Zhou (Harvard), Franklin J. Wong (Harvard), Jonathan A. Kurvits (Brown), and Shriram Ramanathan (Harvard). The work was supported by the Air Force Office of Scientific Research (FA9550-10-1-0026 and FA9550-12-1-0189), Army Research Office (W911NF-14-1-0669), Department of Education (P200A090076) and National Science Foundation (EECS-0846466 and EECS-1408009).

####

For more information, please click here

Contacts:
Kevin Stacey

401-863-3766

Copyright © Brown University

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

Researchers develop artificial building blocks of life March 8th, 2024

How surface roughness influences the adhesion of soft materials: Research team discovers universal mechanism that leads to adhesion hysteresis in soft materials March 8th, 2024

Two-dimensional bimetallic selenium-containing metal-organic frameworks and their calcinated derivatives as electrocatalysts for overall water splitting March 8th, 2024

Curcumin nanoemulsion is tested for treatment of intestinal inflammation: A formulation developed by Brazilian researchers proved effective in tests involving mice March 8th, 2024

Govt.-Legislation/Regulation/Funding/Policy

What heat can tell us about battery chemistry: using the Peltier effect to study lithium-ion cells March 8th, 2024

Researchers’ approach may protect quantum computers from attacks March 8th, 2024

The Access to Advanced Health Institute receives up to $12.7 million to develop novel nanoalum adjuvant formulation for better protection against tuberculosis and pandemic influenza March 8th, 2024

Optically trapped quantum droplets of light can bind together to form macroscopic complexes March 8th, 2024

Possible Futures

Two-dimensional bimetallic selenium-containing metal-organic frameworks and their calcinated derivatives as electrocatalysts for overall water splitting March 8th, 2024

Curcumin nanoemulsion is tested for treatment of intestinal inflammation: A formulation developed by Brazilian researchers proved effective in tests involving mice March 8th, 2024

The Access to Advanced Health Institute receives up to $12.7 million to develop novel nanoalum adjuvant formulation for better protection against tuberculosis and pandemic influenza March 8th, 2024

Nanoscale CL thermometry with lanthanide-doped heavy-metal oxide in TEM March 8th, 2024

Chip Technology

New chip opens door to AI computing at light speed February 16th, 2024

HKUST researchers develop new integration technique for efficient coupling of III-V and silicon February 16th, 2024

Electrons screen against conductivity-killer in organic semiconductors: The discovery is the first step towards creating effective organic semiconductors, which use significantly less water and energy, and produce far less waste than their inorganic counterparts February 16th, 2024

NRL discovers two-dimensional waveguides February 16th, 2024

Optical computing/Photonic computing

Optically trapped quantum droplets of light can bind together to form macroscopic complexes March 8th, 2024

New chip opens door to AI computing at light speed February 16th, 2024

HKUST researchers develop new integration technique for efficient coupling of III-V and silicon February 16th, 2024

NRL discovers two-dimensional waveguides February 16th, 2024

Discoveries

What heat can tell us about battery chemistry: using the Peltier effect to study lithium-ion cells March 8th, 2024

Researchers’ approach may protect quantum computers from attacks March 8th, 2024

High-tech 'paint' could spare patients repeated surgeries March 8th, 2024

Nanoscale CL thermometry with lanthanide-doped heavy-metal oxide in TEM March 8th, 2024

Announcements

What heat can tell us about battery chemistry: using the Peltier effect to study lithium-ion cells March 8th, 2024

Curcumin nanoemulsion is tested for treatment of intestinal inflammation: A formulation developed by Brazilian researchers proved effective in tests involving mice March 8th, 2024

The Access to Advanced Health Institute receives up to $12.7 million to develop novel nanoalum adjuvant formulation for better protection against tuberculosis and pandemic influenza March 8th, 2024

Nanoscale CL thermometry with lanthanide-doped heavy-metal oxide in TEM March 8th, 2024

Military

What heat can tell us about battery chemistry: using the Peltier effect to study lithium-ion cells March 8th, 2024

The Access to Advanced Health Institute receives up to $12.7 million to develop novel nanoalum adjuvant formulation for better protection against tuberculosis and pandemic influenza March 8th, 2024

New chip opens door to AI computing at light speed February 16th, 2024

NRL discovers two-dimensional waveguides February 16th, 2024

Photonics/Optics/Lasers

Nanoscale CL thermometry with lanthanide-doped heavy-metal oxide in TEM March 8th, 2024

Optically trapped quantum droplets of light can bind together to form macroscopic complexes March 8th, 2024

HKUST researchers develop new integration technique for efficient coupling of III-V and silicon February 16th, 2024

A battery’s hopping ions remember where they’ve been: Seen in atomic detail, the seemingly smooth flow of ions through a battery’s electrolyte is surprisingly complicated February 16th, 2024

Research partnerships

Researchers’ approach may protect quantum computers from attacks March 8th, 2024

How surface roughness influences the adhesion of soft materials: Research team discovers universal mechanism that leads to adhesion hysteresis in soft materials March 8th, 2024

'Sudden death' of quantum fluctuations defies current theories of superconductivity: Study challenges the conventional wisdom of superconducting quantum transitions January 12th, 2024

Development of zinc oxide nanopagoda array photoelectrode: photoelectrochemical water-splitting hydrogen production January 12th, 2024

NanoNews-Digest
The latest news from around the world, FREE




  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project