Abstract

Conventional lasers built on dielectric cavities cannot have dimensions smaller than half the optical wavelength due to the diffraction limit of light. This long-standing barrier can be overcome with plasmonic nanocavities that rely on surface plasmons (SPs), which are collective electron oscillations at a metal-dielectric interface. These SP modes can provide feedback on the nanometer scale and open the path to lasing as long as an optical gain medium placed near the metal nanostructure compensates for dissipative losses. This new compact coherent source has been named “SPASER” or plasmon laser.¹⁾ Since plasmon modes have no cutoff, SPASER can offer coherent optical fields at truly nanometer scales.

© 2015 Japan Society of Applied Physics, Optical Society of America