Steven T. Cundiff
University of Michigan
地点：唐仲英楼B501
时间：2016-05-18 14:30
The concept of multidimensional Fourier transform spectroscopy originated in NMR where it enabled the determination of molecular structure. In either NMR or optics, a sample is excited by a series of pulses. The key concept is to correlate what happens during multiple time periods between pulses by taking a multidimensional Fourier transform. The presence of a correlation, which is manifest as an off-diagonal peak in the resulting multidimensional spectrum, indicates that the corresponding resonances are coupled. Migrating multidimensional Fourier transform spectroscopy to the infrared and visible regimes is difficult because of the need to obtain full phase information about the emitted signal and for the phase difference between the excitation pulses to be stable and precisely incremented. I will give an introduction to optical two-dimensional coherent spectroscopy, using an atomic vapor as simple test system, but also show unexpected results due to atomic interactions. I will then present our use of it to study optical resonances in semiconductor nanostructures. In quantum wells, our results show that many-body effects dominate the light-matter interaction for excitons in semiconductors and provide a rigorous and quantitative test of the theory. In quantum dots, there is inhomogeneous broadening due to size dispersion, however two-dimensional coherent spectroscopy can make size-resolved measurements without the need to isolate individual quantum dots.
Steven T. Cundiff is the Harrison M. Randall Collegiate Professor of Physics and Professor of Electrical Engineering and Computer Science at the University of Michigan.Professor Cundiff received BA in Physics from Rutgers University in 1985 and his Ph.D. in Applied Physics from the University of Michigan in 1992. After receiving his Ph.D., he spent 2 years at University of Marburg, Germany as a post-doctoral Alexander von Humboldt Fellow and then 2 ½ years at Bell Laboratories in Holmdel N.J. In 1997 he joined JILA in Boulder Colorado. JILA is a joint institute between the University of Colorado and the National Institute of Standards and Technology (NIST). From 2004 to 2009 he served as Chief of the NIST Quantum Physics Division.Professor Cundiff works in the area of ultrafast optics, which generally involves producing and using ultrashort pulses of light. He has worked extensively on using these pulses to perform time-resolved spectroscopy. He was involved in some of the first demonstrations of optical frequency combs generated by mode-locked lasers, which revolutionized optical frequency metrology, enabled the generation of isolated attosecond pulses and are essential for optical atomic clocks. Cundiff also works on technologies for generating ultrashort pulses of light.Professor Cundiff is a Fellow of the American Physical Society, of the Optical Society of American and of the Institute of Electrical and Electronic Engineers. He has receive the Meggers Award in Spectroscopy from the Optical Society and an Alexander von Humboldt Research Award.