Date: Tuesday, March 4, 2014
Time: 11:00 am
Speaker: Prof. Matthew Pelton, University of Maryland, Baltimore
Title: Optical Studies of Nanoscale Physics: Semiconductor Nanoplatelets, Vibrating Metal Nanoparticles, and Metal-Semiconductor Assemblies
Location: 67-3111 Chemla Room
Semiconductor nanocrystals and metal nanoparticles are key building blocks for nanophotonics, because they both interact strongly with light in a way that can be tuned by changing the size, shape, and composition of the particles. Time-resolved optical measurements on these particles can thus be used to probe physical mechanical processes on ultrafast time scales and nanometer length scales. I will discuss some recent examples of how this can be done.
(1) Flat, thin colloidal semiconductor nanocrystals, or nanoplatelets, strongly confine electrons and holes in only one direction. This leads to novel carrier dynamics in these materials, and means that they can provide optical gain with low thresholds.
(2) Plasmon resonances can be used to track the mechanical oscillations of metal nanoparticles in solutions, and the high frequencies of these vibrations reveal novel, non-Newtonian behavior even in simple liquids.
(3) Calculations indicate that a single semiconductor nanocrystal can induce nearly complete transparency in the much stronger optical extinction of a plasmonic metal nanostructure, and that this transparency can be dynamically reversed into an induced absorption when exciting with ultrafast laser pulses. This represents a first step towards coherent control over the spatiotemporal flow of optical energy in nanostructures. Realization of these strongly coupled structures will require new fabrication approaches.