Findings are detailed in a paper appearing online in the journal Nature that reports on work conducted by researchers at Purdue, Norfolk State University and Cornell University.

"We have demonstrated the feasibility of the nanolaser ... as a practical technology," said Vladimir Shalaev, a profesor at Purdue University.

The "spaser-based nanolasers" are spheres 44 nanometers in diameter. The spheres were fabricated at Cornell, with Norfolk State and Purdue performing the optical characterization needed to determine whether the devices behave as lasers.

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.

The spasers contain a gold core surrounded by a glasslike shell filled with green dye. When a light is shined on the spheres, plasmons generated by the gold core are amplified by the dye. The plasmons are then converted to photons of visible light, emitted as a laser.

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, according to Purdue researchers.

The researchers, however, have overcome this hurdle 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.

"It's fitting that we have realized a breakthrough in laser technology as we are getting ready to celebrate the 50th anniversary of the invention of the laser," Shalaev said.

The first working laser was demonstrated in 1960.

The current spaser research 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, director of the Birck Nanotechnology Center in Purdue's Discovery Park.

The work was funded by the National Science Foundation and U.S. Army Research Office.