October 30, 2014
4pm - 5pm
Small Hall, Room 111
300 Ukrop Way
Williamsburg, VA 23185Map this location
The development of reliable ultrafast pulsed lasers meaning lasers emitting picosecond or shorter pulses has enabled unprecedented measurements of non equilibrium dynamics in matter. In particular, I will present how this type of laser in a pump-probe configuration can be used to measure the relaxation, thermalization, diffusion, and recombination processes of photoexcited electrons in thin film structures of direct gap semiconductors. These types of materials are the fundamental building blocks that emit, control, and sense light in optoelectronic devices, so it is critical to understand the carrier dynamics of these materials as a function of doping, alloying, film thickness, etc. I will also present how I model the effect of the photoexcited carrier dynamics on the optical properties of the film and use this to determine the scattering, diffusion, and recombination rates for a given sample. These processes play important roles in the performance of optoelectronic devices. The pump-probe method is also an effective tool to investigate the dynamics of the optically induced insulator-metal transition in novel materials such as VO2 and NbO2. Recently we have configured a new setup to make these measurements in the Ultrafast Lab of Prof. Lukaszew and I will present some of our preliminary experimental results. These types of materials show great promise for passive light control and innovative all-optical sensing and switching. The nature of the ultrafast optical response of these materials though is not yet understood, and these types of measurements will be a key piece for solving this puzzle.