New Spaser-Based Nanolaser for Future Optical Technologies

August 17, 2009 - 1:58 am | 82 views

Technology.am (Aug. 17, 2009) — Researchers have created the tiniest laser nearly 50 years ago. Now Researchers at Purdue, Norfolk State University and Cornell University have developed the new device, called a “spaser,” which is the first of its kind to emit visible light with a wavelength of 525 nanometers.

Spaser stands for Surface Plasmon Amplification by Stimulated Emission of Radiation.

The phenomenon represents a critical component for possible future technologies based on “nanophotonic” circuitry. Such circuits will require a laser-light source, but current lasers can’t be made small enough to integrate them into electronic chips. Now researchers have overcome this obstacle, harnessing clouds of electrons called “surface plasmons,” instead of the photons that make up light, to create the tiny spasers.

The “spaser-based nanolasers” created in the research were spheres 44 nanometers, or billionths of a meter, in diameter – more than 1 million could fit inside a red blood cell. The spheres perform the optical characterization needed to determine whether the devices behave as lasers.

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.

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.

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.

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.

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