“World’s Smallest Laser” Announced

A simulation of the spaser shows the device emitting visible light with a wavelength of 525 nanometers. Image courtesy of Birck Nanotechnology Center, Purdue University

Researchers have announced the creation of a light source with a diameter of 44 nm. Dubbed the smallest laser ever made, the device is more accurately described as a “spaser”—an acronym for surface plasmon amplification by stimulated emission of radiation. The breakthrough could pave the way for a host of innovations including superfast computers that use light instead of electrons to process information, advanced sensors and imaging. The spaser is the first of its kind to emit visible light and thus represents a critical component for future technologies based on nanophotonic circuitry, says Vladimir Shalaev, a Professor at Purdue University.

Nanophotonics could lead to advances such as powerful “hyperlenses” that substantially improve the resolution of sensors and microscopes and the computing power of electronics. But nanophotonic circuits require a light source smaller than those produced by conventional laser technology. The researchers overcame this obstacle by harnessing clouds of surface plasmons instead of the photons. “Here, we have demonstrated the feasibility of the most critical component— the nanolaser — essential for nanophotonics to become a practical technology,” Shalaev says.

The “spaser-based nanolasers” created in the research were spheres 44 nm, in diameter – more than 1 million could fit inside a red blood cell. The spheres were fabricated at Cornell, with Norfolk State and Purdue performing the optical characterisation needed to determine whether the devices behave as lasers.

The findings confirm work by physicists David Bergman at Tel Aviv University and Mark Stockman at Georgia State University, who first proposed the spaser concept in 2003.

“This work represents an important milestone that may prove to be the start of a revolution in nanophotonics, with applications in imaging and sensing at a scale that is much smaller than the wavelength of visible light,” said Timothy D. Sands, the Director of the Birck Nanotechnology Center in Purdue’s Discovery Park.

The spasers contain a gold core surrounded by a glasslike shell filled with green dye. When a light was shined 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.

“It’s fitting that we have realised a breakthrough in laser technology as we are getting ready to celebrate the 50th anniversary of the invention of the laser,” Shalaev says.

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

More information on the research is available from the Purdue University press release.

Tags: laser, nanophotonics, Purdue University, spaser, Vladimir Shalaev