Electromagnetically Induced Transparency Effect And Its Applications In GaAs/AlGaAs Semiconductor Quantum Wells

Electromagnetically induced transparency (EIT), which is a quantuminterference effects among the transitions of atomic levels induced by laser in theinteraction process of laser and atomic system, can render an otherwise opaquemedium transparent to the light field. For the traditional way of laser interaction withmedium, a strong light field is generally utilized to avoid weak nonlinearity in thefar-off resonant excitation schemes. For the resonant excitation medium, the strongnonlinear effect can be obtained, but there is the behavior of a very large opticalabsorption. However, EIT opens up an avenue to explore new possibilities forobtaining strong optical nonlinearity of the weak light in the resonant medium, andhave recently attracted considerable attention in the field of nonlinear optics.Meanwhile, EIT can give rise to a significant reduction of the group velocity of theoptical pulse, and result in a momentous change of the dispersion properties as well asa great enhancement of Kerr nonlinearity. It is also possible to realize EITphenomenon in semiconductor quantum wells due to their discrete energy levels.Such a system also has the inherent advantages such as large electric dipole momentsof the transitions, high nonlinear optical coefficients, small size as well as easilyoperating and integrating. Consequently, it is of interest to extend the quantumcoherent and interference effects from atomic system to semiconductor nanostructures,not only for comprehending of the nature of quantum coherence and interferenceeffects in semiconductor nanostructures, also for the possible realization of opticaldevices based on such coherent and interference properties. The thesis is divided intofour chapters, which is organized as follows:In the first chapter, we introduce the elementary knowledge, the basic conceptand theory of EIT. In particular, based on the EIT effects, we spotlight the work of theslow light and optical storage, as well as the enhanced Kerr nonlinearity. Finally, wepresent the methods of our study and give a briefly summary of our work.As a matter of fact, the cross-coupling relaxation of longitudinal-optical phononsplays a major role in the intersubband transitions between the subbands of conductionband. We study analytically the characteristics of optical absorption and slow-lightsolitons based on interband transitions in an asymmetrical four level N configurationsemiconductor quantum wells with the cross-coupling relaxation of longitudinal optical phonons in chapter two. It is shown that, in the linear range, a nearly perfectdual-EIT phenomemon occurs with the help of increasing the intensity ofcross-coupling. In the nonlinear range, the amplitude of solitons reveals parabolicchanges which also obtain a maximum value with the increase of cross-couplecoefficient. The group velocity of the solitons continuously slows down if there arefixed three-photon detunings.In contrast to interband transitions, there are intersubband transitions of thesubband of conduction band in the GaAs/AlGaAs quantum wells EIT medium. Inchapter three, we present a feasible scheme to implement two-qubit controlled-phasegate of the polarization state of the photons in a four-level asymmetric GaAs/AlGaAsquantum wells. By analyzing the nonlinear optical response of the probe and signaloptical pulsed fields, it is found that the cross-Kerr nonlinearity is greatly enhancedunder the condition of mutually matched group velocities, as well as enables efficientphoton-photon entanglement and produces conditional nonlinear phase shifts of orderπ in such a system. In addition, by using linear optics components, we propose apractical experimental scheme to discriminate the maximally entangled polarizationstate of the two-qubit.Finally, we make a brief summary of our work and look forward to a furtherinvestigation on the related phenomena of EIT in the field of nonlinear optics.