In 2018, a team from Northwestern University demonstrated a tunable nanolaser that can preserve its high mode quality by exploiting hybrid quadrupole plasmons as an optical feedback mechanism.
[8] The spaser is a proposed nanoscale source of optical fields that is being investigated in a number of leading laboratories around the world.
Spasers could find a wide range of applications, including nanoscale lithography, fabrication of ultra-fast photonic nano circuits, single-molecule biochemical sensing, and microscopy.
Similarly to a laser, the energy source for the spasing mechanism is an active (gain) medium that is excited externally.
As such, surface plasmons can undergo stimulated emission, accumulating in a single mode in large numbers, which is the physical foundation of both the laser and the spaser.Study of the quantum mechanical model of the spaser suggests that it should be possible to manufacture a spasing device analogous in function to the MOSFET transistor,[10] but this has not yet been experimentally verified.