(Invited) Dynamics of Light-Matter Interactions in Plasmonic Optical Cavities for Characterizing Nanostructures Relevant to Energy Conversion and Photocatalysis

Abstract

Optical cavities are an established means to increase light-matter interactions with a wide range molecules, nanostructures and bulk materials. The use of an optical cavity to increase the likelihood of photon absorption by a material has clear potential for being of value for optical energy conversion and photocatalysis. Furthermore, optical cavities can significantly alter excited state dynamics due to the potential for Purcell effects that increase radiative rates of emission of a given material, molecule, or nanostructure. These dynamic changes can serve as a sensing mechanism of cavity impact to photoprocesses, making characterization tools such as transient absorption and time-resolved emission measurements an effective means to probe the degree of light-matter coupling. Taken a step further, these characterization tools can help establish the degree of light-matter coupling necessary to control excited state lifetimes for a particular purpose or application. Here, we explore the dynamics of nanostructured systems coupled to, or made out of, plasmonic materials. Importantly, plasmonic structures are well-known to serve as a type of optical cavity, and though plasmonic cavities are lossier than their dielectric counterparts, they can also confine light to a small mode volume which is very helpful for increasing photonic interactions with nanostructures. The focus of this talk is on materials and nanostructures of interest for solar energy conversion or photocatalysis, such plasmonic nanoparticles and semiconducting nanoparticles, which are interacting with or functioning as, a plasmonic cavity. The plasmonic cavity can be as simple as a thin metal film that supports a propagating surface plasmon polariton (SPP). We also explore refractory plasmonic systems due to their potential durability and reduced likelihood of melting under optical illumination as compared to noble metal nanostructures. The dynamics of nanostructure photoprocesses as a function of photon energy relative to the cavity resonance is explored in detail and impact on applications is described. Work performed at the Center for Nanoscale Materials, a U.S. Department of Energy Office of Science User Facility, was supported by the U.S. DOE, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.