This project advanced understanding about how interactions between nanoscale materials and light can be manipulated, leading to optical structures with unique properties and functionalities. Through computational and experimental approaches, the research team demonstrated plasmonic nanostructures that support next generation energy efficient electronics, such as nanoscale lasers, advanced communications, quantum science and sensing technologies.

Specifically, we have investigated the light-matter interactions at the nanoscale by integrating quantum emitters, such as organic molecules or semiconducting quantum dots, with individual or arrays of plasmonic nanostructures. We demonstrated that, for a plasmon-assisted hybrid organics/inorganics structure, both high spontaneous emission and Forster resonance energy transfer rates can simultaneously occur, and a high decay rate of donor due to the Purcell effect can result in a limited energy transfer efficiency. We also demonstrated a method to engineer light polarization confined within sub-10 nm hot spots by utilizing small tips of plasmonic nanostar resonators. We have theoretically investigated the efficient long-range inter-emitter quantum entanglement and large enhancement of resonance energy transfer between two optical qubits mediated by epsilon-near-zero and other plasmonic waveguide types, such as V-shaped grooves and cylindrical nanorods.

We have demonstrated the coherent random lasing by the scattering of emitted photons from plasmonic gold nanostars embedded in a dye medium. The highly engineered sub-10 nm tips of the nanostars provide effective scattering centers. We have experimentally demonstrated a method to directly guide the random lasing mode into a single-mode optical fiber which provides a convenient means to collect and guide the poorly spatial coherent random lasing through guided modes. Directional coherent lasing emission from periodic arrays of plasmonic nanostructures has also been demonstrated.

We have discovered that plasmonic waveguide modes of film-coupled nanoparticles can significantly boost the optical nonlinearities. Specifically, we demonstrated an approximately four orders of magnitude enhancement of the second order harmonic generation in film-coupled nanowaveguides. Furthermore, by integrating quantum emitters with nanowaveguides, second order nonlinear exciton-polariton states are demonstrated with a Rabi splitting energy of 19 meV. The nonlinear frequency conversion using the hybrid film-coupled plasmonic nanowaveguides thus provides an excellent platform for nonlinear control of the light-matter interactions that has a great potential for applications in optical engineering and quantum information processing. Furthermore, we have discovered exceptional points of epsilon-near-zero plasmonic waveguide systems that provide a route towards interesting nanophotonic applications, such as reflectionless active epsilon-near-zero media, unidirectional coherent perfect absorbers, nanolasers, strong optical bistability and all-optical switching nanodevices.

This project has contributed to the research training of undergraduate and graduate students in nanospectroscopy, nanofabrication, electronic and photonic nanomaterials science. Undergraduate students participated in the "Nanomaterials Meet Metamaterials" activities offered by the PI at the University of Memphis (UofM) while at the University of Nebraska-Lincoln (UNL) undergraduate students participated in the annual "Bright Lights NanoCamp" organized by the Nebraska Center for Materials and Nanoscience. Outreach activities have been performed to provide 11^th and 12^th grade students with fundamental working experience in the PI's research lab through the UofM summer CRESH (College Research Experience for Students in High Schools) program. Both laboratories of the PI and co-PI have hosted NSF REU students.

Last Modified: 10/21/2021
Modified by: Thang B Hoang