Ultrafast terahertz response of optically excited semiconductor heterostructures

摘要

A microscopic theory for the terahertz response of a semiconductor quantum well under coherent conditions is presented. It is shown that excitonic effects influence the intersubband absorption under certain conditions. For high-quality samples, one should be able to resolve both band-to-band and excitonic intersubband transitions in an terahertz absorption measurement. Due to the competition of intersubband transitions and classical field-induced carrier accelerations, an unexpected Fano feature is observed in the terahertz spectra. This result is in excellent agreement with recent measurements.