Fano effect due to ponderomotive coupling in intersubband response of semiconductor quantum wells

M. Baudisch, M. Wagner, H. Schneider, D. Stehr, M. Helm, P. Atkinson, Y. Huo, O. G. Schmidt, A. M. Andrews, and G. Strasser

Phys. Rev. B 86, 075305 – Published 13 August 2012

Abstract

Using terahertz-time-domain spectroscopy, it has been demonstrated before that an intersubband transition in photoexcited undoped quantum wells reveals a Fano-like line shape in transmission spectra due to the phase-sensitive coupling of ponderomotive and intersubband currents [D. Golde et al., Phys. Rev. Lett. 102, 127403 (2009)]. In the present experimental study on GaAs/AlGaAs quantum wells we attempt to delineate the observability conditions of this phenomenon. We find that intensity-based Fourier-transform infrared (FTIR) spectroscopy cannot uncover these ponderomotive effects. However, for time-domain spectroscopy they are shown not to be limited to the case of optically excited electrons, but can be seen in doped samples as well.