Femtosecond and quasi-steady-state optical nonlinear physics of GaAs/AlAs type-II quantum wells
Understand optical nonlinearities in GaAs/AlAs quantum well is motivated to a great extent by the technological importance of GaAs/AlAs heterostructures in devices such as diode lasers (e.g. mirrors), resonant tunneling devices, and optoelectronic devices. These structures are grown by modern epitaxial techniques such as molecular beam epitaxy (MBE) which can control semiconductor layer thicknesses to within an atomic monolayer. The linear and nonlinear optical properties of GaAs/AlAs type-II quantum wells under femtosecond and continuous-wave excitation are presented in this thesis. The photoluminescence (PL) spectra in type-II QWs exhibit and additional line due to the radiative recombination of spatially separated electrons and holes. This additional information is utilized to develop a new spectroscopic technique which allows a direct measurement of the quantum-confinement energy (QCE) shifts in the valence band, independent of the QCE shifts in the conduction band. The QCE shifts are used to determine the conduction- and valence-band discontinuities without the use of any fitting parameters. In addition, the interfacial roughness responsible for the inhomogeneous broadening of the optical transitions is determined. The nonlinear optical properties of type-II QWs are dramatically influenced by the spatial separation of the electrons and holes. The nonlinear effects of many-body interactions on the absorption spectrum with femtosecond and nanosecond optical pulses are investigated. Under extremely high excitation conditions, optical gain and an ultra-fast nonlinear response in type-II GaAs/AlAs MQWs are observed. In addition, the dependence of the optical gain and absorption nonlinearities on the dependence of the optical gain and absorption nonlinearities on the distribution of electrons between the GaAs and AlAs layers is investigated through the application of a static electric field perpendicular to the epitaxial layers.
- Research Organization:
- Stanford Univ., CA (United States)
- OSTI ID:
- 121168
- Resource Relation:
- Other Information: TH: Thesis (Ph.D.); PBD: 1992
- Country of Publication:
- United States
- Language:
- English
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