We have experimentally measured the 1-2 intersubband absorption in a single 40 nm wide modulation-doped Al0.3Ga0.7As/GaAs square quantum well as a function of frequency, intensity, and charge density. The low-intensity depolarization-shifted absorption occurs near 80 cm(-1) (10 meV or 2.4 THz), nearly 30% higher than the intersubband spacing. At higher intensities, the absorption peak shifts to lower frequencies. Our data are in good agreement with a theory proposed by Zaluzny, which attributes the redshift to a reduction in the depolarization shift as the excited subband becomes populated.

VL - 76 SN - 0031-9007 N1 - Sherwin, Mark S/Q-4762-2017Sherwin, Mark S/0000-0002-3869-1893; Markelz, Andrea/0000-0003-0443-4319

78 ER - TY - JOUR T1 - NONLINEAR QUANTUM DYNAMICS IN SEMICONDUCTOR QUANTUM-WELLS JF - Physica D-Nonlinear Phenomena Y1 - 1995 A1 - Sherwin, M. S. A1 - Craig, K. A1 - Galdrikian, B. A1 - Heyman, J. A1 - Markelz, A. A1 - Campman, K. A1 - Fafard, S. A1 - Hopkins, P. F. A1 - Gossard, A. AB -

We discuss recent measurements of the nonlinear response of electrons in wide quantum wells driven by intense electromagnetic radiation at terahertz frequencies. The theme is the interplay of quantum mechanics, strong periodic driving, the electron-electron interaction and dissipation. We discuss harmonic generation from an asymmetric double quantum well in which the effects of dynamic screening are important. Measurements and theory are found to be in good agreement. We also discuss intensity-dependent absorption in a 400 Angstrom square quantum well. A new nonlinear quantum effect occurs, in which the frequency at which electromagnetic radiation is absorbed shifts to the red with increasing intensity. The preliminary experimental results are in agreement with a theory by Zaluzny, in which the source of the nonlinearity is the self-consistent potential in the Hartree approximation for the electron dynamics.

VL - 83 SN - 0167-2789 N1 - Sherwin, Mark S/Q-4762-2017Sherwin, Mark S/0000-0002-3869-1893; Markelz, Andrea/0000-0003-0443-4319

14th Annual International Conference of the Center-for-Nonlinear-Studies - Quantum Complexity in Mesoscopic Systems

May 16-20, 1994

Los alamos, nm

Ctr nonlinear studies

34 ER -