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Smallest Nanolaser Could Open New Era of Smaller, Faster Photonic Devices

by Editor1 last modified July 28, 2012 - 10:05

Researchers from University of Texas at Austin, in collaboration with researchers in Taiwan and China, have developed the world's smallest semiconductor laser, invisible to the naked eye.

Smallest Nanolaser Could Open New Era of Smaller, Faster Photonic Devices

The team used a single nanorod placed on a thin silver film (28 nm thick). The resonant electromagnetic field is concentrated at the 5-nm-thick silicon dioxide gap layer sandwiched by the semiconductor nanorod and the atomically smooth silver film.

The work was led by Chih-Kang "Ken" Shih, professor of physics at University of Texas at Austin.

Made small enough, nanoscale lasers could improve performance of computer chips, biosensors, communications technologies and other photonic devices. Nanolasers also generate optical signals and transmit information, and may even replace electronic circuits.

But researchers looking to make nanolasers small enough for small, higher-powered photonic devices have been stymied by what is called the three-dimensional optical diffraction limit. The Shih team’s work represents a breakthrough – the first operation of a continuous-wave, low-threshold laser below the 3-D diffraction limit.

"We have developed a nanolaser device that operates well below the 3-D diffraction limit. We believe our research could have a large impact on nanoscale technologies," Shih said.

The device is constructed of a gallium nitride nanorod partially filled with indium gallium nitride. Both alloys are commonly in LEDs. The nanorod is placed on top of a thin insulating layer of silicon and covers a layer of thin-film silver that Shih and his team have been working on more than 15 years.

Inside the Smallest Nanolaser
"Size mismatches between electronics and photonics have been a huge barrier to realize on-chip optical communications and computing systems," said Shangjr Gwo, professor at National Tsing Hua University in Taiwain and a former doctoral student of Shih's.

When fired, the team’s nanolaser emits a green light. The laser is too small to be visible to the naked eye. "We have developed a nanolaser device that operates well below the 3-D diffraction limit. We believe our research could have a large impact on nanoscale technologies," Shih said.

The atomic smoothness of the thin-film material is a key to building photonic devices that don't scatter and lose plasmons, which are waves of electrons that can be used to move large amounts of data. "Atomically smooth plasmonic structures are highly desirable building blocks for applications with low loss of data," said Shih.

Nanolasers using this approach could help be a key component to on-chip communication systems, where all processes are contained on the chip. On-chip designs would keep heat low and avoid information loss when passing data between chips, according to Shih.

The team reported their efforts in Science.