Coherent effects are studied in a dense atomic vapor driven by laser fields. With optical properties dramatically modified by these effects, the medium can be used to manipulate some of the properties of laser field. Our experiments demonstrate the coherent control over transmission, spatial distribution and noise feature of the laser field interacting with coherent media. The results have potential applications in the field such as precision metrology, precision spectroscopy, optical imaging and lithography. We develop an experiment to investigate the atomic excitation by few-cycle radio frequency (RF) pulses interacting with Zeeman sublevels. The system provides the flexibility to fully control all parameters of RF pulses. Such a flexibility can not be achieved in optical domain. Based on this system, experiments can be conducted to simulate processes in ultra-short laser physics. In particular, we study the carrier-envelope effect of few-cycle pulses and the strong off-resonant excitation by short pulses. We also discuss the selective reflection spectrum on a highly dense atomic vapor in which the dipole-dipole interaction can not be neglected. The spectrum broadening due to dipole-dipole interaction is much broader than the Doppler broadening. Our experiments show that the excitation by a pump laser can reduce the dipole-dipole interaction, thus reduce the broadening and improve the spectral resolution. The excitation dependence is studied at various atomic densities.

This work is devoted to the study of the quantum coherent effects in diatomic molecular systems by using high resolution laser spectroscopy. In particular, we have studied the rubidium diatomic molecular gaseous medium's absorption spectrum with high resolution single mode laser spectroscopy. The derived electronic and rotational vibrational constants were used in the backward Raman amplification experiment of Rb diatomic molecule. Both experimental results and theoretical calculation confirms that there is strong backward directionally dependent radiation. This effect can further be utilized in remote detection of chemical material. In the saturated spectroscopy experiment of the cesium diatomic molecule, long-lived ground state coherence was observed. The coherence would decay at a rate less than the natural life time of the excited states, which indicates great possibility for performing the quantum optics experiments previously performed in atomic systems only. Electromagnetically induced transparency has been observed in many atomic systems for many years, while it has been seldom realized in molecular systems. In our experiment of electromagnetically induced transparency in cesium diatomic molecules, we utilized  energy levels, and observed subnatural linewidth. This is the first time to realize a  type EIT in a molecular ensemble. This experiment will lead to many other experiments of quantum effects in a molecular system, such like magnetic optical rotation, light storage in ensemble of molecules. Magnetically induced chirality in an atomic ensemble is also investigated in my research.

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also from UMI/Dissertation Abstracts International.

Thesis (Ph. D.)--Drexel University, 2004. / Includes abstract and vita. Includes bibliographical references (leaves 116-118).

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references (leaves 88-98). Available also in a digital version from Dissertation Abstracts.

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