The world’s smallest semiconductor laser has been developed by physicists from The University of Texas at Austin, collaborating with colleagues in Taiwan and China. The laser is so small that it is not visible to the naked eye.
It is a breakthrough in the theoretical miniaturization of photonics technology and could have applications ranging from computing to medicine. The subdiffraction nanolaser, based on surface plasmon amplification by stimulated emission of radiation, was reported in the July 27, 2012 issue of Science.
Miniaturization of semiconductor lasers is an important technology for the development of faster, smaller and lower energy photon-based electronics, for example ultrafast computer chips, highly sensitive biosensors for detecting, treating and studying disease, and next-generation communication technologies.
“We have developed a nanolaser device that operates well below the 3-D diffraction limit,” says Chih-Kang “Ken” Shih, physics professor at The University of Texas at Austin. “We believe our research could have a large impact on nanoscale technologies.”
This marks the first operation of a continuous-wave, low-threshold laser below the 3-D diffraction limit. When fired, the nano-laser emits green light.
Gallium Nitride Nanorod
The device is made of a gallium nitride nano-rod , partially filled with indium gallium nitride. Both alloys are semiconductors used commonly in LEDs. The nanorod is placed on top of a thin insulating layer of silicon that in turn covers a layer of silver film that is smooth at the atomic level.
This is a material that Shih and his researchers have been perfecting for more than 15 years. That “atomic smoothness” of the metallic film is key to building photonic devices that don’t scatter and lose plasmons. Plasmons are waves of electrons that can be used to move large amounts of data. The plasmonic nanocavity is formed in between an atomically smooth epitaxial silver film and a single optically pumped nanorod consisting of an epitaxial gallium nitride shell and an indium gallium nitride core acting as gain medium.
“Atomically smooth plasmonic structures are highly desirable building blocks for applications with low loss of data,” said Shih.
Nano-laser semiconductors such as this may one day allow the development of chips where all processes are contained on the chip, so-called “on-chip” communication systems. This would prevent heat gains and information loss typically associated with electronic devices that pass data between multiple chips. Of course, manufacturing such a chip in production scale quantities presents a completely new set of challenges which would need to be overcome.
1. Plasmonic Nanolaser Using Epitaxially Grown Silver Film
Yu-Jung Lu, Jisun Kim, Hung-Ying Chen, Chihhui Wu, Nima Dabidian, Charlotte E. Sanders, Chun-Yuan Wang, Ming-Yen Lu, Bo-Hong Li, Xianggang Qiu, Wen-Hao Chang, Lih-Juann Chen, Gennady Shvets, Chih-Kang Shih, Shangjr Gwo
Science 27 July 2012: Vol. 337 no. 6093 pp. 450-453 DOI: 10.1126/science.1223504