Quantum dots as midinfrared emitters

Feb 23, 2009 By Miranda Marquit feature

(PhysOrg.com) -- “People are interested in the mid-infrared,” Dan Wasserman tells PhysOrg.com. Infrared light has a wavelength longer than visible light, and many molecules have numerous very strong optical resonances in the midinfrared. “Because of this, the midinfrared is an important wavelength range for trace gas sensing applications.” In addition the midinfrared is also of interest for applications such as thermal imaging, countermeasures, and even free space communication.

Right now, much of the work that takes place with regard to emitting light in the mid-infrared range is done with what are known as quantum cascade lasers, complex structures consisting of hundreds of connected quantum wells. Wasserman, a scientist at the University of Massachusetts Lowell, believes that - for some applications at least - indium arsenide (InAs) quantum dots could be used as an alternative to the quantum wells in quantum cascade lasers.

Wasserman, along with his graduate student, Troy Riboudo at Lowell, Prof. Steve Lyon at Princeton University in New Jersey, and Drs. Ken Lyo and Eric Shaner at Sandia National Laboratory in Albuquerque, have developed a device that uses InAs quantum dots as midinfrared emitters. Their work is presented in Applied Physics Letters: “Room temperature midinfrared electroluminescence from InAs quantum dots.”

“One of the main problems with quantum cascade lasers,” Wasserman points out, “is that they emit in a frequency range close to thermal energies. These lasers sometimes make heat instead of light. If you could enhance optical transitions over thermal, then they would be more efficient emitters, since there would be less power going to the heat.”

Wasserman also says that with quantum cascade lasers, the geometry is two dimensional, and that means that emission, without complicated fabrication techniques, comes from the sample edges, rather than the surface. “Our design works similarly to the quantum cascade laser, but since we are growing quantum dots, we are using a 3-D geometry that emits from the surface. This 3-D geometry also makes thermal transitions in the dot less likely, an effect known as the ‘phonon bottleneck’.”

Could a midinfrared light emitter such as Wasserman describes actually replace quantum cascade lasers? “It would presumptuous to think so,” Wasserman insists. “However, there are some cases where this quantum dot device might be more efficient. But I don’t think that this would be an outright replacement. It would just be an alternative for some situations and device requirements.” He points out that nanoscale surface emitters of midinfrared light, such as these quantum dots, would be ideal for an array that could complete lab on a chip applications.

“We still have a ways to go before the quantum dot devices can even approach quantum cascade lasers, though,” Wasserman concedes. “We grew quantum dot samples that were not designed for lasing. As a result, we would need to design a waveguide in order to confine the dot emission and give us gain, and ultimately, lasing in these structures.” He also says that right now the quantum dots are only grown in a single layer. “In order to get the kind of power we would need for lasing applications, we’d need more layers. So we’re looking into that as well.”

“The important thing is that we showed that this is possible. We can design these special structures that work similarly to a quantum cascade laser, but that have the potential to improve on the efficiency in certain situations. We have some room in the design space to play around, and we’ll see where this can go.”

More Information: Wasserman, et. al. “Room temperature midinfrared electroluminescence from InAs quantum dots.” Applied Physics Letters (2009). Available online: link.aip.org/link/?APPLAB/94/061101/1 .

Copyright 2009 PhysOrg.com.
All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com.

Explore further: Bake your own droplet lens

add to favorites email to friend print save as pdf

Related Stories

MIT researchers build an all-optical transistor

Jul 04, 2013

Optical computing—using light rather than electricity to perform calculations—could pay dividends for both conventional computers and quantum computers, largely hypothetical devices that could perform ...

Gold nanoparticles: A new delivery for cancer drugs

May 08, 2013

(Phys.org) —The protein tumor necrosis factor-alpha (TNF-alpha) is a powerful weapon in the arsenal to control cancer. Unfortunately, as is the case with many potent cancer therapies, the use of TNF-alpha as an anti-cancer ...

Researchers crack full-spectrum solar challenge

Jun 26, 2011

In a paper published in Nature Photonics, U of T Engineering researchers report a new solar cell that may pave the way to inexpensive coatings that efficiently convert the sun's rays to electricity.

Quantum dots track who gets into cell nucleus

Sep 02, 2010

(PhysOrg.com) -- UC Berkeley researchers Karsten Weis, Jan Liphardt, and colleagues have used fluorescent probes called quantum dots to determine which molecules get into the nucleus via its nano-pores and ...

When noise becomes the signal

Mar 24, 2010

(PhysOrg.com) -- European researchers have developed a new class of electronics that uses noise -- normally a problem -- as part of the signal. It means better, faster electronics.

Recommended for you

Bake your own droplet lens

8 hours ago

A droplet of clear liquid can bend light, acting as a lens. Now, by exploiting this well-known phenomenon, researchers have developed a new process to create inexpensive high quality lenses that will cost ...

Precise control of optical frequency on a chip

Apr 23, 2014

In the 1940s, researchers learned how to precisely control the frequency of microwaves, which enabled radio transmission to transition from relatively low-fidelity amplitude modulation (AM) to high-fidelity ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

Alexa
not rated yet Feb 23, 2009
midinfrared is also of interest for applications such as thermal imaging, countermeasures, and even free space communication
... by another words, quantum dot technology is still unable to produce lasers, which could burn you through fog, so it can be used in other areas.

More news stories

Phase transiting to a new quantum universe

(Phys.org) —Recent insight and discovery of a new class of quantum transition opens the way for a whole new subfield of materials physics and quantum technologies.

A 'quantum leap' in encryption technology

Toshiba Research Europe, BT, ADVA Optical Networking and the National Physical Laboratory (NPL), the UK's National Measurement Institute, today announced the first successful trial of Quantum Key Distribution ...

When things get glassy, molecules go fractal

Colorful church windows, beads on a necklace and many of our favorite plastics share something in common—they all belong to a state of matter known as glasses. School children learn the difference between ...

One in 13 US schoolkids takes psych meds

(HealthDay)—More than 7 percent of American schoolchildren are taking at least one medication for emotional or behavioral difficulties, a new government report shows.

FDA reconsiders behavior-modifying 'shock devices'

(HealthDay)—They're likened to a dog's "shock collar" by some and called a "life-saving treatment" by others. But the days of electro-shock devices as a tool for managing hard-to-control behavior in people ...

Computer program could help solve arson cases

Sifting through the chemical clues left behind by arson is delicate, time-consuming work, but University of Alberta researchers teaming with RCMP scientists in Canada, have found a way to speed the process.