Femto-fast and Nano-small: Ultrafast Spectroscopy of Semiconductor Nanostructures
Semiconductor nanostructures such as quantum wells, quantum wires and quantum dots have increasing number of applications in the fields of science, technology and medicine. Some critical material properties including optical responses strongly depend on the many-body states of carriers and their dynamics. The characteristic time scale of the carrier dynamics ranges from a few femtoseconds to hundreds of picoseconds. Femtosecond lasers provide unprecedented time resolution to study the carrier dynamics in such materials. One of the advanced ultrafast spectroscopic techniques is Optical Multi-dimensional Fourier Transform Spectroscopy. The concept of multi-dimensional Fourier transform spectroscopy originated in nuclear magnetic resonance (NMR) where it revolutionized NMR studies of molecular structure and dynamics and led to the Nobel Prize in Chemistry in 1991. In the past decade, the same concept has been implemented in the optical region with femtosecond lasers. In this presentation, I will introduce Optical Multi-dimensional Fourier Transform Spectroscopy and its applications to study dynamics of quantum systems. Both 2D and 3D spectra of a potassium atomic vapor will be presented as a test case to validate the method. I will then present the use of multi-dimensional spectroscopy to study many-body states and carrier dynamics in semiconductor quantum wells and quantum dots.
Hebin Li is currently an assistant professor in the Department of Physics at Florida International University. He studies the interaction of light with matter by using cutting-edge optical tools. He is particularly interested in many-body quantum systems consisting of interaction atoms, molecules and electrons. He develops and uses techniques and ideas in ultrafast spectroscopy and quantum optics to probe and manipulate quantum dynamics of such systems. He received his B.S. in physics from Wuhan University in 2001, and his Ph.D. in physics from Texas A&M University in 2010. Before joining the faculty at FIU in 2013, he worked as a Research Associate at JILA, a joint institute of the National Institute of Standards and Technology (NIST) and the University of Colorado at Boulder. For more information, please visit his website at http:/faculty.fiu.edu~hebin/.