We present a time-resolved technique to measure optical excitation processes with a time resolution shorter than the oscillation period of the exciting light. Our terahertz (THz) experiments fully resolve the polarization dynamics of electrons in semiconductor heterostructures when they are excited by a THz pulse. The time resolution of the polarization enables us to deduce the population dynamics of the excited state, which includes the dynamics of a virtual population in the case of off-resonant excitation.
© 2000 Optical Society of America
(270.1670) Quantum optics : Coherent optical effects
(300.6240) Spectroscopy : Spectroscopy, coherent transient
(320.7130) Ultrafast optics : Ultrafast processes in condensed matter, including semiconductors
(320.7150) Ultrafast optics : Ultrafast spectroscopy
R. Kersting, R. Bratschitsch, G. Strasser, K. Unterrainer, and J. N. Heyman, "Sampling a terahertz dipole transition with subcycle time resolution," Opt. Lett. 25, 272-274 (2000)