Elucidation of Hot-Electron Transport and Exploitation of Hot-Carrier Plasmonics via Nonlinear Optical Effects

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The behavior of energetic electrons, termed “hot” electrons, is essential for applications in chemical synthesis, energy harvesting, and information technology. Further advances of this area of research demand deepened knowledge of the behavior of such charged electrons after excitation with light. This excitation process is a complicated phenomenon consisting of a number of sequential processes, most of which happen within one billionth of a second. This research team controls the behavior of these hot electrons with other optical effects to understand the generation, transport, and decay of electrons. Moreover, the ultrafast behavior of optically induced hot electrons is harnessed for the all-optical control of light. The knowledge gained through this project lays the groundwork at the interface of semiconductors and optics, and leads to new insights into the design and implementation of devices for the detection and processing of light. This research, included with high school and collegiate education, promotes multidisciplinary thinking of the up-and-coming scientists and engineers. The project broadly disseminates interdisciplinary knowledge derived from this research effort, encourages early engagement of the youth via integration of research and education, and enhances the learning opportunities for high school students from minority groups.The dynamics of plasmonically induced hot carriers is pivotal to a wide range of photophysical and photochemical processes. The current understanding is partially constrained by the capacities of prevailing characterization methods. Moreover, the fundamentals and applications of hot-carrier plasmonics are predominantly focused on the linear optical regime, while rather limited work has investigated the involvement of hot carriers in nonlinear light-matter interactions. This project aims to elucidate the dynamics of the generation, transfer, and thermalization of hot carriers via nonlinear optical means, and furthermore, to exploit hot-carrier induced nonlinear optical processes for signal detection and processing in photonic and quantum systems. The overall content of this research is to establish a new technique for the investigation and utilization of the ultrafast dynamics of hot carriers based on the second- and third-order nonlinear optical effects. Such novel nonlinear processes are explored in hybrid plasmonic platforms, where nanostructured metals interface electron-accepting materials. Of particular interest are the implementations of two hot-carrier induced phenomena, namely, the transient optical Kerr nonlinearity and the transient second-harmonic generation, for the investigation of hot-electron dynamics and the realization of ultrafast all-optical control of light. The successful execution of the research leads to new understanding of light-matter interactions at reduced dimensions, and facilitates improved understanding of hot-carrier physics, optical signal processing, and quantum transport.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.