Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Nanotubes Surprise Again: Ideal Photon Emission

08.09.2003


Carbon nanotubes, recently created cylinders of tightly bonded carbon atoms, have dazzled scientists and engineers with their seemingly endless list of special abilities – from incredible tensile strength to revolutionizing computer chips. In today’s issue of Science, two University of Rochester researchers add another feat to the nanotubes’ list: ideal photon emission.



"The emission bandwidth is as narrow as you can get at room temperature," says Lukas Novotny, professor of optics at Rochester and co-author of the study. Such a narrow and steady emission can make such fields as quantum cryptography and single-molecule sensors a practical reality.

The emission profile came as a surprise to Todd Krauss, assistant professor of chemistry at the University, and Novotny. They had set out to simply define the emission, or fluorescence, of a single carbon nanotube. By using a technique called confocal microscopy, the team illuminated a single nanotube with a strongly focused laser beam. The tube absorbed the light from the laser and then re-emitted light at new frequencies that carried information about the tube’s physical characteristics and its surroundings.


The light emitted from the nanotube was in precise, discrete wavelengths, unlike most objects like molecules that radiate into a broader (i.e. more "fuzzy") range of wavelengths at room temperature.

But a greater surprise was in store for the team.

"The emission wasn’t just perfectly narrow, it was steady as far as we could measure," says Krauss. In a strange quirk of quantum physics, molecules usually emit their photons for a certain time and then cease, only to resume again later, like a telegraph signal. The tubes that Krauss and Novotny measured, however, remained steady beacons to the limits of their instruments’ sensitivity. "This is very exciting because for any application in quantum optics, you want a steady and precise photon emitter," says Novotny.

Narrow emissions and a complete absence of blinking have tempting implications for single photon emitters--devices needed to dependably release a single photon on command. The U.S. Department of Defense is very interested in developing quantum cryptography, a theoretically unbreakable method of coding information, which necessitates a reliable way to deliver single photons on demand.

Other applications come in the form of sensors so sensitive they can detect a single molecule of a substance. For example, when a biological molecule such as a protein binds to a nanotube, the nanotube’s perfect emission changes, revealing the presence and characteristics of the molecule. Detecting the change would be impossible if it weren’t for the remarkably steady nature of the nanotube emission, because a researcher wouldn’t know for certain if a sudden change in the emission was just a blink, or was meant to indicate the presence of the target molecule.

Until just a few months ago, determining the emission characteristics of a nanotube was impossible. Carbon nanotubes cannot be made individually-rather they come as a jumble like a pile of spaghetti. Trying to measure the photon emission of a tube in the jumble is impossible because the tube will pass the photons it absorbs to other tubes instead of re-emitting them in its telltale fashion. What scientists end up with is a sort of average of what the collection of tubes will emit--not the emission characteristics of a single tube. Only within the past few months have researchers figured out how to remove a single nanotube from the pile of spaghetti in order to study its properties as an individual.

Krauss and Novotny are now devising experiments to test the steadiness of the nanotube fluorescence beyond the range of the initial experiments, and are pursuing studies aimed at determining the ultimate minimum possible emission bandwidth at ultracold temperatures.

This work was funded by the National Science Foundation, the U.S. Department of Energy, the Research Corporation, and the New York State Office of Science and Academic Research.

Jonathan Sherwood | University of Rochester
Further information:
http://www.rochester.edu/pr/News/NewsReleases/scitech/Krauss-Novotny.html

More articles from Physics and Astronomy:

nachricht Study offers new theoretical approach to describing non-equilibrium phase transitions
27.04.2017 | DOE/Argonne National Laboratory

nachricht SwRI-led team discovers lull in Mars' giant impact history
26.04.2017 | Southwest Research Institute

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Fighting drug resistant tuberculosis – InfectoGnostics meets MYCO-NET² partners in Peru

28.04.2017 | Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

 
Latest News

Wireless power can drive tiny electronic devices in the GI tract

28.04.2017 | Medical Engineering

Ice cave in Transylvania yields window into region's past

28.04.2017 | Earth Sciences

Nose2Brain – Better Therapy for Multiple Sclerosis

28.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>