June 23, 2010 feature
Carbon nanotubes show the ability to amplify light, could lead to new photonic applications
(PhysOrg.com) -- "Carbon nanotubes have a lot of really nice properties that make them good for photonics," Laurent Vivien tells PhysOrg.com. Ever since the discovery that carbon nanotubes have photoluminescence when encapsulated in micelle surfactant, Vivien points out, there has been interest in pursuing them for use in nanophotonics, and in microelectronics.
As encouraging as photoluminescence in carbon nanotubes has been, though, scientists also need to see that they could be investigated as optical sources. The ability to amplify light is vital for this purpose. Vivien, a CNRS scientist at the Institute of Fundamental Electronics at the University Paris-Sud in Orsay, France, is part of a team that has demonstrated that optical gain is possible with carbon nanotubes. Along with a team from the Institute, as well as the National Institute of Advance Industrial Science and Technology in Tsukuba, Japan, Vivien has published the group’s findings in Applied Physics Letters: “Optical gain in carbon nanotubes.”
“Our demonstration is the first step to reach a laser source based on carbon nanotubes that can be used in photonics,” Vivien explains. “The first step is to demonstrate that gain can be seen in the material, and we have done that, showing that carbon nanotubes can amplify light.”
The demonstration of optical gain was relatively straightforward in III-V materials, but it was the first time in carbon nanotubes. The team used a polymer assisted extraction technique: a semiconducting single-walled carbon nanotube doped thin layer was dropped onto glass. The sample was then excited with the help of a laser, and the results observed. The scientists in the group noted that the light was, in fact, amplified.
“Now that we have seen that carbon nanotubes can produce this effect, the next step is to build a laser based on carbon nanotubes,” Vivien says. He points out that it should be possible to insert a carbon nanotube inside an optical resonator in order to make a laser. “This method could lead to a laser with the capability to emit at several wavelengths according to the nanotube geometry, which could be suitable for many photonic applications.”
Other possibilities for photonics based on carbon nanotubes include telecommunications and possible microelectronics. “It should be possible to make photonic circuits based on carbon nanotubes,” Vivien says, “and the semiconducting nature of these nanotubes could also make them useful in electronics. These carbon nanotubes are versatile, and with them you can make several building blocks for many different applications.”
Vivien and his colleagues plan to focus first on building a laser based on carbon nanotubes, rather than exploring the possibilities in microelectronics; other scientists might be able to pick up on that work. “While I see other potential applications following this demonstration, I am most interested in photonics,” he explains. “This really is a good first step toward a new photonics based on carbon nanotubes. This could be less expensive, flexible and used in many applications.”
“Semiconducting carbon nanotubes offer a very good material,” Vivien continues. “There are a number of desirable properties for a wide variety of applications. These nanotubes are low cost, modular and flexible. This is a breakthrough for photonics using carbon nanotubes and could lead to a whole new photonics in the future.”
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