  Localized surface plasmon resonances have recently attracted considerable
attention due to their ability to dramatically enhance near-field optical
intensities and boost nanoscale light-matter interactions. Here we demonstrate
unambiguously that polyhedral silver nanoparticles can be tailored to promote
enhanced coherent emission from organic dye dispersions in a cavity. In
particular, we observe that nanoparticles supporting resonances close to the
absorption peak of the dye yield to more efficient lasing, up to one order of
magnitude, which is also evidenced by the narrowing of the emission spectral
line down to 3 nm. Moreover we observe emission saturation and energy dependent
spectral shifts associated with Kerr effects, which demonstrate the general
relevance of non-resonant nonlinearities in plasmonic enhanced laser emissions.
Works in this area will contribute to the design of novel kind of laser sources
providing ultra-short pulsed operation and structural tunability.
