Dresden 2009 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 13: Optical properties

HL 13.2: Talk

Tuesday, March 24, 2009, 09:45–10:00, BEY 118

Excitonic signatures in the intersubband THz absorption of optically excited semiconductor quantum wells — •Daniel Golde, Mackillo Kira, and Stephan W. Koch — Fachbereich Physik, Philipps-Universität, Renthof 5, D-35032 Marburg

We present a theoretical study of the intersubband absorption of an optically excited undoped semiconductor quantum well using our recently developed microscopic THz theory [1]. In the past, intersubband transitions were often studied using doped quantum wells. In this case, the absorption follows entirely from the equilibrium carrier distribution in the lowest subband. For photoexcited quantum wells, however, there are two distinct contributions to the intersubband response. The optically generated charge carriers can be excited to a higher subband giving rise to usual band-to-band transitions. The optical pump pulse can also create an excitonic polarization which is under certain conditions converted into an incoherent exciton population [1]. We show that the presence of such coherent or incoherent excitons yields additional excitonic THz transitions that are spectrally different from the band-to-band transitions.

In my talk, I will show how the intersubband absorption is influenced by excitons and for which experimental conditions one can expect to observe them in a measurement.

[1] M. Kira and S. W. Koch, Prog. Quantum Electron. 30, 155 (2006).