Lasing From Single Film-Coupled Nanoparticles

Abstract

Plasmonic nanostructures and metamaterials have found many applications as small-scale sources of controllable emission. Of particular interest is utilizing these types of structures as potential coherent radiation sources. Plasmonic Film-coupled Nanoparticles(FCNP), or nanopatch antennas, are good candidates for low-threshold, room-temperature nanolasing that can be predicted analytically. In this dissertation, I present results from multiphysical numerical models used to validate the predictions of a recent analytical theory, using optical pump intensity, population inversion, and pump photon count as metrics of lasing threshold. I show that a single cylindrical nanopatch antenna made of silver with an embedded fluorescent dye is capable of lasing at a threshold on the order of $10^4$ W/cm$^2$. I go beyond the hypotheses of the theoretical model by investigating the impact of spectrally non-separated absorption and emission transitions through the influence of lasing signal/absorption line and pump/emission line interactions. Furthermore, I tighten the model constraints and analytical predictions to facilitate experimental verification and ultimately demonstrate predicted lasing behavior. Thresholds on the order of $10^5$ W/m$^2$ are verified from fabricated experimental samples through spectral and coherence measurements of emission as a function of incident optical pump intensity from single film-coupled nanocubes with a variety of embedded dyes corresponding favorable geometric and material parameters. Agreement between analytically predicted thresholds and experimentally measured thresholds validates the previously developed theory and demonstrates the utility of the single film-coupled nanoparticle platform for lasing.