Combined Optical and Terzhertz Control of Semiconductor Nanostructures

Regents Of The University Of Michigan - Ann Arbor, Ann Arbor MI

Investigators

Abstract

This research project concerns the use of coherent optical and terahertz (THz) fields to control the phase and population of electrons, holes, and excitons in semiconductor quantum structures, including quantum wells and normal-mode microcavities. Coherent optical and single-cycle terahertz (THz) pulses will be generated by means of femtosecond lasers. The combined use of optical and THz pulses opens up new possibilities for the generation and control of electron-hole wavepackets in semiconductors. Three general areas of research will be explored: (1) Coherent Control of Microcavities and Optical Analogies to Quantum Transport, (2) THz Emission from Excitonic Wavepackets, and (3) THz probes of Exciton and Polariton Dynamics. These experiments will allow us to explore the semiconductor optical analogies to processes of great interest in other fields of physics, namely single-particle transport of electrons in quantum systems, and the generation of high harmonics in the ionization of atoms by short intense laser pulses. Graduate and undergraduate students as well as post doctoral research associates will participate in this research. %%% When light shines on a semiconductor material, electrons which are tightly bound to the atoms in the material are "freed up" to move throughout the semiconductor. If the wavelength (color) of the optical excitation is chosen properly, these form states called "excitons" which behave in many ways analogously to a hydrogen atom. Over the past few decades, many optical experiments were performed to study the properties of these excitons. With the recent advent of femtosecond laser technology, it has become possible to not only generate excitons, but to control them as well. Our program will take a novel approach to the control of excitons, by using simultaneous optical and far-infrared (terahertz frequency) pulses to manipulate the electrons in the semiconductor. The basic science being investigated is important from a technological point of view, because the interface between high-speed (terahertz) electronics and optics is one of the fundamental problems which must be addressed for the further development of high-speed communications and computers. This research will engage the collaboration of graduate and advanced undergraduate students and post doctoral research associates. They will receive training in a contemporary forefront area of science and technology and thereby prepare them for entry into the scientific/technological workforce. ***