Optically pumped gold nanorod plasmonic microlaser

High optical field intensities build up inside microtoroids owing to its ultra-high quality factor, making them an ideal platform for plasmonic-photonic interactions with noble metals and a suitable pump source for microlaser. In this work, a microlaser based on hybrid silica microtoroids coated with gold nanorods is theoretically modeled and experimentally demonstrated. Theoretically, we used 3-D Comsol Multiphysics and modeled the interaction between the optical mode of the microtoroids and the surface plasmonic resonance of gold nanorods, both on and off resonance. To thoroughly study the role that the polymer layer plays in the plasmonic laser system, we perform a series of finite element method simulations in which the polymer layer thickness and refractive index is varied, and its effect on the plasmonic resonance is quantified. Experimentally, we demonstrated a visible laser at 575nm from hybrid microtoroids with a 30μWthreshold and an approximately 1nm linewidth. We have also varied the gold nanorod concentration on the microtoroids surface, and studied its effect on the Quality factor and the threshold power in order to get the optimum concentration for lasing.