Microsphere Exhibits Chip-Scale Lasing

Combining nanoplasmonic devices and optical microresonators can produce laser-like light emission, potentially paving the way for power-on-a-chip applications.

“We have made optical systems at the microscopic scale that amplify light and produce ultranarrowband spectral output,” said Dr. J. Gary Eden, a professor of electrical and computer engineering at University of Illinois at Urbana-Champaign. “These new optical amplifiers are well-suited for routing optical power on a chip containing both electronic and optical components.”

The researchers used a 10-µm polystyrene sphere — a microsphere — that, when activated by an intense beam of light, internally generated a narrowband optical signal via Raman scattering.

A hybrid optoplasmonic system showing the operation of amplification. Courtesy of Nathan Bajandas/Beckman Institute at the University of Illinois at Urbana-Champaign.

Molecules tethered to the surface of the sphere by a protein amplified the Raman signal, the researchers said. In concert with a nanostructured surface connected to the sphere, the amplifier produced visible light with a bandwidth that matched the internally-generated signal.

“In our design, we use Raman-assisted injection-seeded locking. In addition to the spectral control afforded by injection locking, the effective Q of the amplifier can be specified by the bandwidth of the injected Raman signal,” said postdoctoral researcher Dr. Manas Ranjan Gartia. “This is an important step forward for monolithically building on-chip light sources inside future chips that can use much less energy while providing superior speed performance of the chips.”

Plasmonics can serve as a bridge between photonics and nanoelectronics to combine the size of nanoelectronics and the speed of dielectric photonics, according to the researchers.

The speed of conventional semiconductor electronics is limited to about 10 GHz, due to heat generation and interconnect delay. Though not limited by speed, dielectric-based photonics are limited in size by the fundamental laws of diffraction.

Potential applications exist in medicine, as “the amplifiers are actuated by light that is able to pass through human skin,” Eden said. Such microsphere-based amplifiers could be used to transmit signals from cells, as well as buried biomedical sensors, to electrical and optical networks outside the body, he added.

The research was published in Scientific Reports (doi: 10.1038/srep06168).

For more information, visit www.illinois.edu.