Quantum Kinetics of Laser-Induced Electron Hole Plasmas in Nanowire Arrays

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The interaction of light with matter is a fundamental topic of scientific research and critical to many modern technologies. The entire research field of optoelectronics is concerned with explaining the quantum interaction of light with electronic material components, increasingly on the scale of atoms and molecules. For many semiconductors, intense laser light can excite electrons, which then leave oppositely-charged shadows behind, known as "holes". These electrons and holes behave as a plasma (a gas of charged particles) confined within the solid. Solving the complicated equations describing such plasmas in three-dimensional space can be prohibitive, even on today's supercomputers. Quantum-wires, however, have a thickness over 1000 times smaller than a human hair, and they allow us to test quantum plasma models on charges that are confined to only one dimension in space. This project aims to calculate the evolution of electron-hole plasmas in interacting quantum wires, as well as the evolution of the light that excites them. The goal is to improve knowledge of optical and transport properties of light-generated plasmas on time-scales of a millionth of a billionth of a second. This knowledge is important for understanding of light-matter interactions, as well as advancements in nano-optoelectronics, sensing, and many national security applications. This project also has significant broader impacts in providing undergraduate students a chance to participate in cutting-edge research, development of new college course curricula based on the research results, and enabling public outreach.On the technical side, the goal of this project is to develop improved calculations of the ultrafast dynamics of photo-excited electron-hole plasmas in quantum wires, as well as the scattering of ultrashort laser pulses incident on a quantum wire array. The computations will couple Pseudo-Spectral Time Domain (PSTD) techniques of modeling light propagation to quantum-kinetic Semiconductor Bloch equations for the many-body plasma dynamics in the quantum wires. This project advances our knowledge of plasma dynamics in solids by dispensing with several common assumptions often used to simplify such calculations; including monochromatic laser fields, electron-hole distributions in quasi-equilibrium, spatially uniform electric fields in the medium, and neglect of longitudinal fields resulting from the spatial electron-hole plasma distribution. These assumptions are a limiting factor on today's optoelectronic calculations involving intense light, particularly on the nanometer length and femtosecond time scales. The project will seek to find experimentally measurable indicators of the correlation between the localized response of quantum-wire plasmas and the spatial-temporal features and phases of the scattered light pulses. It will also look for a measurable correlation between the current from driven electron-hole plasmas, as well as localized longitudinal electromagnetic fields due to induced, long-lasting plasma oscillations in the quantum wires. The results of the project will also be important for advancements in the emerging fields of femtosecond electronics and attosecond physics.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.