Ultrafast and quantum dynamics of plasmonic nanolasing

Lasers have in recent years become smaller and smaller, reaching with the demonstration of plasmonic nanolasing, scales much smaller than the wavelength of the light they emit [1, 2]. Such plasmonic nanolasers employ plasmonic resonances for feedback, allowing them to concentrate light into mode volumes that are no longer limited by diffraction. But it does not stop there. Next to this dramatic reduction in cavity size, plasmonic lasers also unlock a number of fundamentally new lasing characteristics and phenomena: (1) Plasmonic Leaky Mode Lasing [3]: While in photonic nanowire lasers leaky modes — waveguide modes that lose part of their energy to the continuum of radiation modes during propagation - are usually prevented from crossing the lasing threshold, plasmonic nanowire lasers remarkably allow leaky mode lasing. Indeed, plasmonic lasers can then be used as coherent sources of surface plasmon polaritons at the nanoscale or as surface plasmon emitting diodes with an emission angle that depends on the nanowire diameter and the color of the surface plasmon polariton. (2) Plasmonic Stopped-light Lasing [4]: The recently established concept of dispersion-less stopped-light [3] allows by combination of nanoplasmonics with quantum gain materials [4] stopped-light lasing in hybrid nanoplasmonic heterostructures. In a stopped-light laser, photons are trapped and amplified in space just at the point of their emission: at stopped-light singularities a stable lasing mode can form over a finite region of gain material due to the arising local (cavity-free) feedback in the form of a sub-wavelength optical vortex. The observed high-β characteristics and picosecond relaxation oscillations of cavity-free stopped-light lasing can potentially allow for the design of thresholdless plasmonic laser diodes that can be modulated with THz speeds. (3) Surface Plasmon Polariton Condensation [5]: Applying stopped-light lasing principle to surface-plasmon polaritons (SPP), also provides an entry point to SPP-condensation, quantum gain in quantum plasmonics and quantum fluids of light.