Event
Ph.D Dissertation Defense: Shangjie Yu
Thursday, April 26, 2018
10:00 a.m.-12:00 p.m.
AVW 2168
Maria Hoo
301 405 3681
mch@umd.edu
ANNOUNCEMENT: Ph.D Dissertation Defense
Name: Shangjie Yu
Committee:
Professor Jeremy Munday, Chair/Academic Advisor
Professor Min Ouyang, Co-Chair/Ph.D. Advisor
Professor Raymond Phaneuf
Professor Christopher Davis
Professor YuHuang Wang, Dean’s Representative
Date/time: Thursday, April 26th, 2018 at 10:00 am - 12:00 pm
Place: AVW 2168
Title: Understanding light-matter interactions at the nanometer scale
Abstract:
There have been novel phenomena and promising applications emerging from the nanoscience and nanotechnology research over the recent decades. Particularly, people pursue a better understanding of how light and matter interact with each other at the nanoscale. This dissertation will present our works on understanding light-matter interactions at a very fine spatial scale, including ultrafast nanoscale phonon coupling and manipulation, metamaterials for thermal management and cooperative chirality in inorganic nano-systems.
Through a acoustically mismatched nanoscale interface, interfacial phonon coupling may lead to a coherently modulated phonon spectrum, which however has been less studied. We have demonstrated unambiguous experimental evidences of coherent interfacial phonon coupling between the core and shell constituents by employing a well-designed nanoscale core-shell structure with a precisely tunable interface as a model system. Furthermore, the observed phonon modes can be selectively tailored in a highly controllable manner by different ultrafast pulse control schemes. This study represents an important step towards nanoscale phonon engineering with rationally tailored nanostructures as building blocks.
Metamaterials, which are artificially patterned micro/nano-structures, are studied for thermal management. For this purpose, we propose patterned arrays in different forms, including micropillar arrays and fiber arrays. We have discovered the structural dependence of the arrays’ characteristic resonance and emission properties, and how the properties are impacted in imperfect patterns which are common in real life. This study provides new perspectives on metamaterials for thermal management and textile industry.
Lastly, chiral light-matter interaction is studied in a novel type of inorganic nanocrystals, consisting of both crystallographic and geometric chirality. We build up a general model for simulating electromagnetic response of chiral objects and extract the materials parameters from experimental data of the achiral-shape nanocrystals. By simulating nanocrystal of different geometries and comparing with experimental circular dichroism spectra, the unique spectral features from the nanocrystals’ intrinsic crystallographic chirality, geometric chirality and their interplay are identified. Besides, an excellent agreement is achieved between the simulation and the experiment. This result opens the opportunities for new chiroptical devices and chiral discrimination technology.