Studies On Nonlinear Optical Characteristic In Quantum Coherent Media And Related Phenomena

In this thesis for the Doctorate, we have discussed mainly nonlinear optical features and its applications in quantum coherent media. More precisely speaking, we theoretically study optical nonlinear enhanced effects, ultralow optical solitons, high-efficiency mixing conversion, coherent control of optical bistability/multistability and spontaneous emission spectra as well as dynamics in both optically dilute and optically dense media.The work of our paper can be divided into the following eight parts:(1)We demonstrate the efficient generation of ultraslow bright and dark optical solitons in a lifetime-broadened three-level atomic medium by using only a low-intensity pulsed laser radiation.(2)The potential for nonlinear conversion between two laser pulses in a three-level V-type medium with assistance of an auxiliary microwave resonant radiation is studied. The results show that microwave driven field can lead to the parametric generation of a new laser pulse with high conversion efficiency when a weak pump laser pulse is applied.( 3 ) We analyze hybrid absorptive-dispersive optical bistability (OB) and multistability (OM) behavior in a generic N-type atomic system driven by a degenerate probe field and a coherent coupling field by means of a unidirectional ring cavity. We show that the OB can be controlled by adjusting the intensity and the detuning of the coupling field, and the OM can also be observed under the appropriate detuning. The influence of the atomic cooperation parameter on atomic OB behavior is also discussed.(4)We analyze hybrid absorptive-dispersive OB behavior via tunable Fano-type interference based on intersubband transitions in asymmetric double quantum wells (QWs) driven coherently by a probe laser field by means of a unidirectional ring cavity. We show that OB can be controlled efficiently by tuning the energy splitting of the two excited states (the coupling strength of the tunnelling), the Fano-type interference, and the frequency detuning. The influence of the electronic cooperation parameter on the OB behavior is also discussed.At the same time, we study OB behavior based on intersubband transitions in an asymmetric coupled-quantum well (CQW) driven coherently by a probe laser field and a control laser field by means of a unidirectional ring cavity. We demonstrate that OB can be controlled by tuning the energy splitting between two tunnel-coupled electronic levels, the intensity of the control field, and the frequency detuning of the probe and control fields. The influence of the electronic cooperation parameter on the OB behavior is also discussed.(5)We investigate the features of the spontaneous emission spectra in a coherently driven cold four-level and five-level atomic systems by means of a radio frequency (rf) or microwave field driving a hyperfine transition within the ground state. It is shown that a few interesting phenomena such as spectral-line narrowing, spectral-line enhancement, spectral-line suppression, and spontaneous emission quenching can be realized by modulating the phase, the frequency and intensity of the rf-driving field in our systems. In the dressed-state picture of the coupling and rf-driving fields, this five-level atomic system is equivalent in form to a real atomic system with multi-channel spontaneous emission coherence. With respect to no existence of the real atomic system with spontaneous emission coherence effect or not finding it, the paper amounts to proposing a feasible scheme of carrying out experimental investigation.(6)Taking the density-dependent near dipole-dipole (NDD) interaction into consideration, we investigate the response of nonlinear absorption and dispersion as well as population dynamics in optically dense media of three-level and four-level atoms driven by a single-mode probe laser. The influence of the NDD effects on the absorption-dispersion of the probe field and population dynamics is predicted via numerical calculations.(7)We investigate the response of the probe amplification in a five-level atomic system in the presence of interacting double-dark resonances disturbed by introducing an additional signal field. It is found that a large enhancement of the probe amplification with or without population inversion can be achieved by properly adjusting the strengths of the microwave driving field and the signal laser field. From viewpoint of physics, we qualitatively explain these results in terms of quantum interference and dressed states.(8)We investigate the features of two-photon absorption in a five-level atomic system with interacting dark resonances. It is found that two-photon absorption can be completely suppressed at two different frequencies due to the application of two coherent coupling fields and the atomic system exhibits double electromagnetically induced transparency windows against two-photon absorption. The position and width of the double two-photon transparency windows can be controlled via properly adjusting the frequency detuning and the intensities of the two coupling fields. In addition, one enhanced narrow central line can be observed in the two-photon absorption spectra, which may find applications in high precision spectroscopy. Form a physical point of view, we explicitly explain these results in terms of quantum interference induced by three different two-photon excitation channels in the dressed-state picture.In summary, these studies may be helpful not only to understand better the new characteristic of nonlinear optics in both the cold atomic media and semiconductor quantum-well material but also to the high techniques of optical information storage and retrieval, the coherent manipulation of atoms, all-optical switching and all-optical storage devices, high-precision spectroscopy as well as quantum information sciences.