We investigate frequency up-conversion of low power cw resonant radiation in Rb vapour as a function of various experimental parameters. We present evidence that the process of four wave mixing is responsible for unidirectional blue light generation and that the phase matching conditions along a light-induced waveguide determine the direction and divergence of the blue light. Velocity-selective excitation to the 5D level via step-wise and two-photon processes results in a Doppler-free dependence on the frequency detuning of the applied laser fields from the respective dipole-allowed transitions. Possible schemes for ultraviolet generation are discussed.
We report on the loading and trapping of ultracold atoms in a one dimensional permanent magnetic lattice of period 10 µm produced on an atom chip. The grooved structure which generates the magnetic lattice potential is fabricated on a silicon substrate and coated with a perpendicularly magnetized multilayered TbGdFeCo/Cr film of effective thickness 960 nm. Ultracold atoms are evaporatively cooled in a Z-wire magnetic trap and then adiabatically transferred to the magnetic lattice potential by applying an appropriate bias field. Under our experimental conditions trap frequencies of up to 90 kHz in the magnetic lattice are measured and the atoms are trapped at a distance of less than 5 µm from the surface with a measured lifetime of about 450 ms. These results are important in the context of studies of quantum coherence of neutral atoms in periodic magnetic potentials on an atom chip.
Atomic media have played a major role in studies of fast light. One of their attractive
features is the ability to manipulate experimental parameters to control the dispersive
properties that determine the group velocity of a propagating light pulse. We give an
overview of the experimental methods, based on both linear and nonlinear atom–light
interaction, that have produced superluminal propagation in atomic media, and discuss
some of the significant theoretical contributions to the issues of pulse preservation and
reconciling faster-than-light propagation and the principle of causality. The comparison of
storage of light, enhanced Kerr nonlinearity and efficient wave mixing processes in
slow and fast light atomic media illustrates their common and distinct features.
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