A Nanolaser, also referred to as a miniature laser or plasmonic laser, is a laser, namely a light amplifier by stimulated emission of radiation, that has nanoscale dimensions. While the word nano originates from Greek νᾶνος (=dwarf), the international system of units has adapted the prefix as a quantifier equal to 10-9. The nanolaser concept was developed by Mark Stockman at Georgia State University in 2003.
Traditionally, a beam of light could not be made smaller (or more strongly confined) than about one-half its wavelength, λ. This fundamental physical limitation is called the diffraction limit of light. In order to achieve a laser with optical mode sizes smaller than this limit, scientists needed to invent a novel way of squeezing light in dimensions about 100 times smaller than a diffraction limited beam, creating an optical hybridized plasmon-mode. Surface plasmons, light on a metallic interface, have the ability to provide strong optical confinement, however they suffer inherent ohmic (resistive) losses. Thus, a nanolaser, while proposed many years ago (as a "plasmon laser") was fundamentally challenging to realize.
A hybrid plasmon approach, however, can combine the best of both words: a strong sub-wavelength optical confinement of nanoscale dimensions with a semiconductor gain medium providing the light amplification. The illustration shows a nanolaser consisting of a semiconductor nanowire forming a cavity, thus providing feedback and the lasing mode confined to 1/100th of the laser wavelength.
This tiny laser can be modulated quickly and, combined with its small footprint, makes it an ideal candidate for on-chip optical computing. The intense optical fields of such a nanolaser also enables the enhancement effect in non-linear optics or surface-enhanced-raman-scattering (SERS), and therefore paves way towards integrated nanophotonic circuitry.
1. ^ Oulton, R. F., Sorger, V. J., Genov, D. A., Pile, D. F. P. & Zhang, X. "A hybrid plasmonic waveguide for sub-wavelength confinement and long-range propagation." Nature Photon. 2, 495–500 (2008)
Definition of a Nanolaser