Abstract
Light-matter interaction is one of the fundamental phenomena of the universe that has greatly impacted the development of the human society, including the evolution of our visual systems and visually guided behavior. In this talk, we present research on light-matter interactions at nanoscale, also known as “nanophotonics”, to help brighten the future of energy sustainability. The applications include dispatchable solar electricity, ultralow-power photonic data links, and color-contrast manipulation of single atomic/molecular layers towards energy-efficient display in the future. Harnessing the interaction between sunlight and transition metal oxide nanoparticles, we designed and implemented solar selective absorbers with a record high optical-to-thermal conversion efficiency of 93.8% at 750 °C using low-cost spray coating for concentrated solar power systems. The coating also passed >1000 h endurance testing at 750 °C in air without deterioration, directly supporting high-efficiency, low-cost solar thermal energy storage towards dispachable solar electricity whenever needed. The optical design methods developed in this project could also be extended to high-efficiency, speckle-free laser lighting technologies. To modulate signals in photonic data links at ultralow power, we synergistically utilize the large electro-optical and electro-absorption effects in GaAs/AlGaAs quantum wells and selectively couple the light into the surface plasma modes at “off” state, thereby achieving 6-20 dB extinction ratio at a low insertion loss of 1-3 dB at ≤1V driving voltage. This innovation enables an “optical bridge” operating at an ultralow power consumption <100 fJ/bit and a high data rate >80 Gb/s, representing 10-20x energy efficiency improvement for optical interconnects in data centers. Lastly, we discuss photon management in 2D materials using self-assembled, ultrahigh refractive index semimetal nanostructures, allowing us to see atomically thin 2D layers with naked eyes through color contrast. Tuning the Fermi levels of the 2D materials and semimetal nanostructures using an electric field could potentially lead to new energy-efficiency, flexible display technologies in the future.
Biography
Dr. Jifeng Liu is currently an Associate Professor at Thayer School of Engineering, Dartmouth College. He also administrates the Materials Science Graduate Program at Thayer School. He received his B.S. and M. S. degrees in Materials Science and Engineering from Tsinghua University, Beijing, China, and his Ph.D. degree from Massachusetts Institute of Technology. His major research field is nanophotonic materials and devices, including integrated photonics for ultralow energy photonic datalinks as well as nanomaterials and nanostructures for novel photodetectors, solar photovoltaics and solar thermal energy harvesting. He has authored or co-authored 78 peer-reviewed journal papers, more than 60 conferences papers, and 6 book chapters, which have been widely cited. Dr. Liu has also been granted 14 U.S. patents related to nanophotonic materials and devices. He received National Science Foundation (NSF) Faculty Early Career Development (CAREER) Award in 2013, and was elected a Senior Member of the Institute of Electrical and Electronics Engineers (IEEE) in 2015.