Plasmonic enhanced photothermal effects and its applications

We review here our recent studies on plasmonic enhanced photothermal effects in metallic nanostructure, and the applications of such effects. When light is shined on a prefect metamaterial absorber patterned with e-beam lithography, the gold nanoparticles (NPs) forming the absorber can be either transformed to nano-spherical-domes, or to truncated-octahedral shaped or multi-twined nanocrystals with large crystal grain sizes and flat boundary facets. The evolution of morphology and crystallinity of the gold NPs can be also observed. Evidences clearly show that the surface melting and the coalescence mechanism play a key role on nanocrystals formation. These melted gold nanospheres can even be transferred to another substrate, on which the transferred NPs exhibit excellent size uniformity. The strong photothermal effects can also be utilized to tune silicon photonics waveguides and resonators. It is shown that all-optical photothermal switching of Mach-Zehnder interferometers (MZI), silicon disk resonators, and silicon ring resonators is possible with the help of plasmonic nanoheaters. The switching response time and power consumption are all at reasonably low level.