World’s tiniest laser paves way for optical computing

West Lafayette, Indiana – Researchers have created the tiniest laser ever, bringing optical computing a step closer to reality.

Nanophotonic circuitry requires a laser-light source, but current lasers can’t be made small enough to be integrated into electronic chips. The new laser achieves this by harnessing clouds of electrons called surface plasmons, rather than photons.

“Here, we have demonstrated the feasibility of the most critical component – the nanolaser – essential for nanophotonics to become a practical technology,” said Vladimir Shalaev, Professor of Electrical and Computer Engineering at Purdue University.

The “spaser-based nanolasers” created in the research were spheres 44 nanometers in diameter. They contain a gold core surrounded by a glasslike shell filled with green dye. When a light was shone on the spheres, plasmons generated by the gold core were amplified by the dye. The plasmons were then converted to photons of visible light, which was emitted as a laser.

Spaser stands for surface plasmon amplification by stimulated emission of radiation. To act like lasers, they require a feedback system that causes the surface plasmons to oscillate back and forth so that they gain power and can be emitted as light. Conventional lasers are limited in how small they can be made because this feedback component for photons, called an optical resonator, must be at least half the size of the wavelength of laser light.

There have been a number of attempts to get round this problem. The Purdue team has done it by using not photons but surface plasmons, which enabled them to create a resonator 44 nanometers in diameter, or less than one-tenth the size of the 530-nanometer wavelength emitted by the spaser.

Future work may involve creating a spaser-based nanolaser that uses an electrical source instead of a light source, which would make it more practical for computer and electronics applications.

Findings are published in Nature.