The possibility for surface plasmons lasers.

We have demonstrated for the first time, attributes of a surface plasmons' laser: threshold, gain, spectral line narrowing and feedback in the visible range. The surface metallic waveguides were consisted of a nano-scale hole-array in a 50 nm thick layer of aluminum oxide on top of aluminum substrate (anodized aluminum oxide or, AAO). In some cases, two-layer graphene was added on top of the perforated oxide layer, as well. The sub-wavelength array of holes enabled coupling to and from the waveguides as well as, providing feedback to the surface modes. The gain media molecules (fluorescein) were imbedded in the structure's pores. Threshold and spectral line narrowing of 30% were clearly demonstrated when pumped with a pulsed laser.