Abstract

Even one decade after the pioneering photon echo experiments by Shank et al.,¹ in which GaAs was investigated at room temperature using ≈10 fs optical pulses, not a single experiment has actually shown directly that the coherent real-time response of semiconductor band-to-band transitions under these conditions is a photon echo indeed. Recent experiments with ≈ 10 fs pulses exciting GaAs at low temperatures have explicitly shown that the response is nor a photon echo for low excitation densities² (≈ 10¹⁵ cm⁻³). From these experiments it has also become clear that the coherent response after excitation with 10 fs pulses is distinctly different from that after excitation with 100 fs pulses.⁴

© 1999 Optical Society of America