| In this dissertation, some novel effects in the interaction processes between coherent fields and nonlinear media, which have been studied both experimentally and theoretically in the past few years, are summarized. A home-made single-mode frequency stabilized CW tunable laser diode system, which can provide coherent light with narrow linewidth ({dollar}sim{dollar}1MHz) and a large frequency tunable range, has been studied, designed, and implemented. A self frequency locking effect has been demonstrated in our experiment to be a general property of laser diode systems with optical (dispersive or non-dispersive) feedbacks. It has also been demonstrated that a large frequency tunable range is virtually achievable in a laser diode system with a weak optical grating feedback. We also demonstrated that under certain conditions, a single-mode diode laser (slave) can be completely controlled by another single-mode laser (master) with an external injection-locking mechanism over the lasing frequency, linewidth, lasing intensity, and intensity fluctuations. An effective self-probed near-degenerate four wave mixing (NDFWM) process has also been observed and studied experimentally.; Electromagnetically induced transparency (EIT) phenomenon in three-level cascade rubidium atoms inside a vapor cell around D{dollar}sb2{dollar} transition lines (780.0nm)has been studied experimentally. Over 64% unsaturated absorption reduction has been observed, while the dispersive properties of the weak probe field in the EIT process was also studied. A new hyperfine spectroscopy technique for the highly-excited atomic states has been demonstrated in the experiment which is the first application of atomic coherence in atomic spectroscopy to the best of our knowledge. A composite system of a normal degenerate optical parametric oscillator coupling with N intracavity two-level atoms has also been studied. The optical bistable behavior of this system is studied. Novel quantum fluctuation properties of this system, including extra intracavity quadrature squeezing in the sub-harmonic mode, the intrinsic structures of quantum fluctuation spectra, and a sub-natural linewidth feature of the atomic spectrum, have been theoretically investigated. |
