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 - TY - JOUR T1 - FAR-INFRARED SATURATION SPECTROSCOPY OF A SINGLE SQUARE-WELL JF - Semiconductor Science and Technology Y1 - 1994 A1 - Craig, K. A1 - Felix, C. L. A1 - Heyman, J. N. A1 - Markelz, A. G. A1 - Sherwin, M. S. A1 - Campman, K. L. A1 - Hopkins, P. F. A1 - Gossard, A. C. AB -

We have performed saturation spectroscopy measurements of the lowest intersubband transition in a single 400 angstrom GaAs/Al0.3Ga0.7As modulation-doped square quantum well. We couple intense tunable far-infrared radiation from the Santa Barbara free electron laser into our sample using an edge-coupling technique and measure absorption as a function of frequency and intensity. Saturation and frequency shifts in the absorption line are clearly observed. We attribute the frequency shifts to reductions in the many-body depolarization shift. From our preliminary measurements, we estimate the intersubband relaxation time to be 600 ps to within a factor of three.

VL - 9 SN - 0268-1242 N1 - Sherwin, Mark S/Q-4762-2017Sherwin, Mark S/0000-0002-3869-1893; Markelz, Andrea/0000-0003-0443-4319

S

8th International Conference on Hot Carriers in Semiconductors

Aug 16-20, 1993

Oxford univ, oxford, england

Sci & engn res council; royal soc; brit council; oxford univ

31 JO - Semicond. Sci. Technol. ER - TY - JOUR T1 - PROBING TERAHERTZ DYNAMICS IN SEMICONDUCTOR NANOSTRUCTURES WITH UCSB FREE-ELECTRON LASERS JF - Journal of Luminescence Y1 - 1994 A1 - Allen, S. J. A1 - Craig, K. A1 - Felix, C. L. A1 - Guimaraes, P. A1 - Heyman, J. N. A1 - Kaminski, J. P. A1 - Keay, B. J. A1 - Markelz, A. G. A1 - Ramian, G. A1 - Scott, J. S. A1 - Sherwin, M. S. A1 - Campman, K. L. A1 - Hopkins, P. F. A1 - Gossard, A. C. A1 - Chow, D. A1 - Lui, M. A1 - Liu, T. Y. AB -

The UCSB free-electron lasers provide kilowatts of continuously tunable radiation from 120 GHz to 4.8 THz. They have the most impact on terahertz science and technology that require a tunable, high power source to explore non-linear dynamics or that sacrifice incident power to recover the linear response of systems with very small cross-section. We describe three experiments that demonstrate the utility of these lasers in experiments on the terahertz dynamics of semiconductor nanostructures: (i) terahertz dynamics of resonant tunneling diodes, (ii) saturation spectroscopy of quantum wells and (iii) photon-assisted tunneling in superlattices.

VL - 60-1 SN - 0022-2313 N1 - Sherwin, Mark S/Q-4762-2017; Guimaraes, Paulo Sergio Soares/B-6918-2012Sherwin, Mark S/0000-0002-3869-1893; Guimaraes, Paulo Sergio Soares/0000-0002-0113-2641; Markelz, Andrea/0000-0003-0443-4319

1993 International Conference on Luminescence (ICL 93)

Aug 09-13, 1993

Univ connecticut, storrs, ct

Univ connecticut; opt soc amer; amer phys soc; ieee, laser & electro opt soc; int union pure & appl phys; int sci fdn; univ connecticut res fdn

3 ER - TY - Generic T1 - Far-infrared nonlinear response of electrons in semiconductor nanostructures T2 - SPIE Proceedings Y1 - 1993 A1 - Sherwin, M. S. A1 - Asmar, N. G. A1 - Bewley, W. W. A1 - Craig, K. A1 - Felix, C. L. A1 - Galdrikian, B. A1 - Gwinn, E. G. A1 - Markelz, A.G. A1 - Gossard, A. C. A1 - Hopkins, P. F. A1 - Sundaram, M. A1 - Birnir, B. JF - SPIE Proceedings VL - 1854 ER -