Polarization dependent beaming properties of a plasmonic lattice laser

We study beaming properties of laser light produced by a plasmonic lattice overlaid with organic fluorescent molecules. The crossover from spontaneous emission regime to stimulated emission regime is observed in response to increasing pump fluence. This transition is accompanied by a strong reduction of beam divergence and emission linewidth due to increased degree of spatial and temporal coherence, respectively. The feedback for the lasing signal is shown to be mainly one-dimensional due to the dipolar nature of the surface lattice resonance. Consequently, the beaming properties along x and y directions are drastically different. From the measurements, we obtain the M-2 value along both principal directions of the square lattice as a function of the pump fluence. Our work provides the first detailed analysis of the beam quality in plasmonic lattice lasers and reveals the underlying physical origin of the observed strong polarization dependent asymmetry of the lasing signal.

Automated summary

In this study, the transition from spontaneous emission to stimulated emission in laser light from a plasmonic lattice overlaid with organic fluorescent molecules is investigated. The reduction of beam divergence and emission linewidth is observed as the pump fluence increases, accompanied by increased spatial and temporal coherence. The one-dimensional feedback for the lasing signal is mainly attributed to the dipolar nature of the surface lattice resonance, resulting in significant differences in beaming properties along x and y directions.