Molecular-scale plasmonic light emission sources
Abstract
Nanoscale metal structures can be designed with plasmonic resonances that are able to support extraordinarily confined electromagnetic fields. Nanoscale plasmonic junctions driven by electrical bias are of great interest as light sources, with potential for quantum optical processes and high-speed modulation of signals. The PI proposes to build on recent observations of giantsynergistic upconversion electroluminescence (EL) and photoluminescence (PL) in gold plasmonic tunneling structures to examine the physics and limitations of the processes at work in these systems. Three specific research questions to be considered are: What are the dominant light emission processes at work in these devices (e.g., amplified stimulated emission; generation of entangled photons; effectively thermal emission)? What limits the energy of the emitted light and the speed of the synergistic coupling between electrical and optical excitation? Can plasmonic nanogaps be combined with gain media in a path toward an electrically pumped plasmonic laser? The technical approach to the first question will use single photon counting tolook at autocorrelation statistics of photon emission. A zero-delay autocorrelation g2(0) of 1 would indicate lasing-like emission via amplification of stimulated emission, while g2(0) of 2 would be consistent with thermal radiation from hot carriers. A value of g2(0) greater than 2 would indicate superbunching, as has been seen in some scanning tunneling microsopy light emission experiments. To test for energy limitations of EL and combined EL+PL, devices willbe fabricated from aluminum, which lacks the interband transitions that limit golds optimal plasmonic emission to comparatively red wavelengths. Pulsed voltage biases down to the nanosecond timescale will be employed to confirm that the EL+PL synergistic process is fast, set by electron-electron scattering rates rather than slower relaxation timescales. EL and EL+PL light emission will also be examined from gold plasmonic junctions in a gain medium, polymerembedded dye molecules with fluorescence resonant with the junction plasmon modes. These measurements are an opportunity to examine strong coupling between molecular emitters and ultraconfined plasmonic modes and may present a path toward electrically driven plasmonic lasers. The anticipated scientific outcomes are (1) an understanding of the fundamental quantumoptical processes involved in emission from molecular-scale plasmonic light sources; (2) a quantitative confirmation of sub-nanosecond modulation times possible in EL+PL, and knowledge of the role of interband transitions in limiting the energy of emitted photons; and (3) emission spectra showing strong couplings between ultraconfined plasmonic modes and molecular emitters. In addition, this work will support the research training of a postdoctoralfellow and a graduate student in nanofabrication, nanophotonics, and the written and oral communications skills needed to disseminate the research results. Successful development of ultrascaled nanophotonic light sources is aligned with DOD technology focus areas, including quantum science (entangled photons) and microelectronics (for information processing, sensing,and communications). This bears directly on ONR nonlinear physics priorities, including nanospasers and nano light sources for potential on-chip optical computing.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 06, 2021
- Source ID
- N000142112062
Entities
People
- Douglas Natelson
Organizations
- Office of Naval Research
- Rice University
- United States Navy