Featured Research

from universities, journals, and other organizations

Etched quantum dots shape up as single photon emitters

Date:
February 26, 2011
Source:
National Institute of Standards and Technology
Summary:
Like snowflakes or fingerprints, no two quantum dots are identical. But a new etching method for shaping and positioning these semiconductor nanocrystals might change that. Tests confirm that etched quantum dots emit single particles of light, boosting prospects for powering new types of devices for quantum communications.

Colorized micrograph of quantum dots made using electron beam lithography and etching. This type of quantum dot can be shaped and positioned more reliably than dots made with conventional crystal growth methods.
Credit: Verma/NIST

Like snowflakes or fingerprints, no two quantum dots are identical. But a new etching method for shaping and positioning these semiconductor nanocrystals might change that. What's more, tests at the National Institute of Standards and Technology (NIST) confirm that etched quantum dots emit single particles of light (photons), boosting prospects for powering new types of devices for quantum communications.

Related Articles


The conventional way to build quantum dots -- at NIST and elsewhere -- is to grow them like crystals in a solution, but this somewhat haphazard process results in irregular shapes. The new, more precise process was developed by NIST postdoctoral researcher Varun Verma when he was a student at the University of Illinois. Verma uses electron beam lithography and etching to carve quantum dots inside a semiconductor sandwich (called a quantum well) that confines particles in two dimensions. Lithography controls the dot's size and position, while sandwich thickness and composition -- as well as dot size -- can be used to tune the color of the dot's light emissions.

Some quantum dots are capable of emitting individual, isolated photons on demand, a crucial trait for quantum information systems that encode information by manipulating single photons. In new work reported in Optics Express, NIST tests demonstrated that the lithographed and etched quantum dots do indeed work as sources of single photons. The tests were performed on dots made of indium gallium arsenide. Dots of various diameters were patterned in specific positions in square arrays. Using a laser to excite individual dots and a photon detector to analyze emissions, NIST researchers found that dots 35 nanometers (nm) wide, for instance, emitted nearly all light at a wavelength of 888.6 nm. The timing pattern indicated that the light was emitted as a train of single photons.

NIST researchers now plan to construct reflective cavities around individual etched dots to guide their light emissions. If each dot can emit most photons perpendicular to the chip surface, more light can be collected to make a more efficient single photon source. Vertical emission has been demonstrated with crystal-grown quantum dots, but these dots can't be positioned or distributed reliably in cavities. Etched dots offer not only precise positioning but also the possibility of making identical dots, which could be used to generate special states of light such as two or more photons that are entangled, a quantum phenomenon that links their properties even at a distance.

The quantum dots tested in the experiments were made at NIST. A final step was carried out at the University of Illinois, where a crystal layer was grown over the dots to form clean interfaces.


Story Source:

The above story is based on materials provided by National Institute of Standards and Technology. Note: Materials may be edited for content and length.


Journal Reference:

  1. V. B. Verma, Martin J. Stevens, K. L. Silverman, N. L. Dias, A. Garg, J. J. Coleman, R. P. Mirin. Photon antibunching from a single lithographically defined InGaAs/GaAs quantum dot. Optics Express, 2011; 19 (5): 4182 DOI: 10.1364/OE.19.004182

Cite This Page:

National Institute of Standards and Technology. "Etched quantum dots shape up as single photon emitters." ScienceDaily. ScienceDaily, 26 February 2011. <www.sciencedaily.com/releases/2011/02/110224091619.htm>.
National Institute of Standards and Technology. (2011, February 26). Etched quantum dots shape up as single photon emitters. ScienceDaily. Retrieved November 23, 2014 from www.sciencedaily.com/releases/2011/02/110224091619.htm
National Institute of Standards and Technology. "Etched quantum dots shape up as single photon emitters." ScienceDaily. www.sciencedaily.com/releases/2011/02/110224091619.htm (accessed November 23, 2014).

Share This


More From ScienceDaily



More Matter & Energy News

Sunday, November 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Toyota's Hydrogen Fuel-Cell Green Car Soon Available in the US

Toyota's Hydrogen Fuel-Cell Green Car Soon Available in the US

AFP (Nov. 21, 2014) Toyota presented its hydrogen fuel-cell compact car called "Mirai" to US consumers at the Los Angeles auto show. The car should go on sale in 2015 for around $60.000. It combines stored hydrogen with oxygen to generate its own power. Duration: 01:18 Video provided by AFP
Powered by NewsLook.com
Google Announces Improvements To Balloon-Borne Wi-Fi Project

Google Announces Improvements To Balloon-Borne Wi-Fi Project

Newsy (Nov. 21, 2014) In a blog post, Google said its balloons have traveled 3 million kilometers since the start of Project Loon. Video provided by Newsy
Powered by NewsLook.com
Raw: Paralyzed Marine Walks With Robotic Braces

Raw: Paralyzed Marine Walks With Robotic Braces

AP (Nov. 21, 2014) Marine Corps officials say a special operations officer left paralyzed by a sniper's bullet in Afghanistan walked using robotic leg braces in a ceremony to award him a Bronze Star. (Nov. 21) Video provided by AP
Powered by NewsLook.com
British 'Bio-Bus' Is Powered By Human Waste

British 'Bio-Bus' Is Powered By Human Waste

Buzz60 (Nov. 21, 2014) British company GENeco debuted what its calling the Bio-Bus, a bus fueled entirely by biomethane gas produced from food scraps and sewage. Jen Markham explains. Video provided by Buzz60
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:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

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