Atomic coherence and quantum interference effects in multi-level atomic systems have attracted great attention in the past decade. Many interesting effects have been observed experimentally such as electromagnetically induced transparency (EIT), dramatic slowing of the speed of light, storage of light pulses in atomic assembles, and enhanced nonlinear optical processes. The research supported by this grant will include studies of nonlinear and quantum dynamical effects in multi-level atomic systems interacting with extremely weak laser beams (at the single-photon level). These studies will increase fundamental understanding of basic physics and lead to discoveries of novel effects. Both linear and nonlinear optical properties in multi-level systems will be greatly modified and controlled experimentally by the induced atomic coherence. Additionally these multi-level atoms will be placed inside an optical cavity so that additional interesting nonlinear and quantum dynamical phenomena can be studied, such as controlling chaos, single-photon switching, quantum logic gates, and quantum tunneling. These fundamental investigations will lead to new discoveries and novel design concepts for optoelectronic devices.
Understanding and controlling nonlinear and quantum dynamical behaviors (such as chaos, stochastic resonance, and tunneling) in these well-controlled laboratory systems can have great impacts in many other areas of sciences with similar complicated nonlinear dynamical behaviors, such as climate, chemistry, biological science, medical science, and other branches of physics. Investigations of nonlinear and quantum effects in the multi-level coherent EIT systems with low light intensities will be essential in developing single-photon all-optical switching or quantum logic gates for quantum information processing and quantum networking, and contributing to future technology advances. Another important benefit in the proposed research is training graduate and undergraduate students working in the fundamental and applied research projects in modern optical laboratory.
. In the past few years, PI and his research group at the University of Arkansas have carried out several experimental investigations of nonlinear and quantum effects in systems involving multi-level atoms interacting with multiple coherent laser fields, especially with multi-level atoms inside an optical ring cavity. Such experimental investigations have greatly helped the understandings of interactions and enhanced nonlinear behaviors between coherently-prepared multi-level atomic systems and coherent laser fields, which can lead to potential applications of those discovered novel effects in opto-electronic devices. The main findings of the funded project include the following: (1) by using the greatly enhanced nonlinear dispersion due to induced atomic coherence to balance the sharp linear dispersion in the medium, the total dispersion for the intracavity field can be tuned to be either positive or negative, which can be used to control the linewidth of the cavity transmission field. This result has potential to be used in pulse shaping and gravitational detection device with signal recycling. (2) PI and his group have demonstrated that the effects (such as Rabi splitting peaks) due to strong interaction between atoms and optical cavity field, typically only observed in cold atoms or atomic beams, can also exist in hot atomic vapors, which have expanded the studies of cavity-QED into a new regime with a high atomic density. (3) In the strongly-coupled atom-cavity system, PI and his group have observed several novel phenomena including lasing without population inversion and further splitting of the above observed Rabi oscillation peaks. (4) Controlled all-optical switching in the multi-level atomic system inside an optical cavity was also experimentally demonstrated, which could be used for information processing. (5) Co-existing high-order nonlinear optical processes, such as four-wave mixing and six-wave mixing, in the multi-level atomic systems were designed and experimentally demonstrated, which significantly expand our understanding for nonlinear interactions between multi-level atomic systems and multiple coherent laser fields. (6) Quantum correlations between generated fields with atom-cavity interactions were experimentally demonstrated and studied. These investigations have resulted in thirty-four refereed journal publications, including three on the most prestigious Physical Review Letters, fifteen on Physical Review A (including 3 on Rapid Communications), three on Optics Letters, two on Applied Physics Letters, two on Optics Express, and one on New Journal of Physics. Also, during the funded time period, PI has published three books (in 2009, 2011, and 2012, respectively) with colleagues on the topics related to the funded projects. These publications have increased the knowledge base for the scientific community and will be useful for designing more efficient opto-electronic devices in the future. This funded NSF project has also trained several graduate, as well as undergraduate, students to work in the PI’s optical laboratory, who are now having productive scientific careers in major US universities. Through High School Days and Undergraduate Research Conferences organized at the University of Arkansas in the past few years, PI’s laboratory has participated in various public education and promotion of science projects.
