• Sep 26 2012

    Stellenbosch Node Seminar: Dr Teodora Kirova

    Stellenbosch Node Seminar: Dr Teodora Kirova

    NITheP cordially invites you to a seminar by:

    Dr Teodora Kirova
    Laser Centre
    Faculty of Physics and Mathematics
    University of Latvia, Riga, LV-1002, Latvia

    Date: Wednesday 26 September 2012
    Time: 14:00
    Venue: NITheP Stellenbosch Node, Seminar Room

    TITLE: Formation of Dark States in Hyperfine Levels of Na via Autler-Townes Effect

    ABSTRACT: We study the formation of dark states and their manifestation in the excitation spectra as a function of Rabi frequency of laser coupling for three-level systems with hyperfine structure. We predict and demonstrate via numerical simulations essential differences between the typical optical Autler-Townes (AT) type of experiments in a three-level ladder (a weak probe field in the first excitation step and a strong coupling field in the second step) and optical pumping type of experiments (a strong pump field in the first excitation step and weak probe in the second step). The key difference in both experiments is that the former would typically establish and observe a steady-state condition, while the latter gives access to the observation of population dynamics. In the AT-type of experiments, the expression of hyperfine structure in the excitation spectra is radically different depending on whether the number of hyperfine levels in the two laser-coupled states is equal or different. In the former case the increase of coupling strength leads to a full expression and resolution Zeeman sublevels associated with the hyperfine structure, while in the latter case a number of sublevels vanish due to the formation of dark states. The optical-pumping type of experiments enable the visualization of dark state formation,which is not possible in the AT-experiments. Due to the population dynamics in the process of optical pumping of adiabatic states, the formation of dark states can be visualized in the probe excitation spectra as bare states are transformed into dark states: the “unmature” dark states or “grey” states are observed in the excitation spectra as peaks which do not change their position as the Rabi frequency of strong coupling is essentially varied.

    Navrae/Enquiries: Rene Kotze
    Tel: 021 808 2653
    Email: renekotze@sun.ac.za

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