Femtosecond laser-pumped plasmonically enhanced near-infrared random laser based on engineered scatterers

In this Letter, we report on the design, fabrication, and implementation of a novel plasmon-mode-driven low-threshold near-infrared (NIR) random laser (RL) in the 850-900 nm range based on plasmonic ZnS@Au core-shell scatterers. Plasmon modes in the NIR region are used for nanoscale scatterer engineering of ZnS@Au core-shell particles to enhance scattering, as against pristine ZnS. This plasmonic scattering enhancement coupled with femtosecond (fs) laser pumping is shown to cause a three-fold lasing threshold reduction from 325 mu J/cm(2) to 100 mu J/cm(2) and a mode Q-factor enhancement from 200 to 540 for ZnS@Au-based RL, as compared to pristine ZnS-based RL. Local field enhancement due to plasmonic ZnS@Au scatterers, as evidenced in the finite-difference time-domain simulation, further adds to this enhancement. This work demonstrates a novel scheme of plasmonic mode coupling in the NIR region and fs excitation in a random laser photonic system, overcoming the inherent deficiencies of weak absorption of gain media and poor scattering cross sections of dielectric scatterers for random lasing in the NIR spectrum. (C) 2017 Optical Society of America