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We experimentally and theoretically investigate in-medium propagation effects of off-resonant light in dense, spatially inhomogeneous ultracold atomic gases. Focussing on frequency modulation spectroscopy as the dispersive detection tool of atoms, we observe that the refractive gradient-index lenses presented by localised atomic ensembles can significantly modify the interpretation of the dispersive signal even for large probe detuning, owing to the collective response of the atoms. We identify criteria for distinguishing between thin and thick atomic lenses, leading to either diffraction-dominated and lensing dominated regimes for the outgoing probe beams. Our findings are consistent with experimental data and solutions of paraxial wave equation for light propagation. Our study provides important practical insights for dispersive, minimally intrusive optical detection and imaging schemes of ultracold atoms and will be valuable for choosing optimal parameter regimes in numerous applications.

We present a method of transferring a cold atom between spatially separated microtraps by means of a Raman transition between the ground motional states of the two traps. The intermediate states for the Raman transition are the vibrational levels of a third microtrap, and we determine the experimental conditions for which the overlap of the wave functions leads to an efficient transfer. There is a close analogy with the Franck-Condon principle in the spectroscopy of molecules. Spin-dependent manipulation of neutral atoms in microtraps has important applications in quantum information processing. We also show that starting with several atoms, precisely one atom can be transferred to the final potential well hence giving deterministic preparation of single atoms., 8 pages, 6 figures. Accepted for publication Journal of Physics B (Atomic, molecular and optical physics)

In this paper, we have studied the isothermal and non-isothermal glass-crystal transition in AgI-doped silver selenomolybdate glasses using differential scanning calorimetry. We have observed a strong dependence of AgI on the glass-crystal transition of these glasses. The activation energy for the crystallization and the dimensionality of the crystal growth for the isothermal and non-isothermal crystallization processes have been determined. The dimensionality of the crystal growth depends strongly on the AgI content and intriguingly shows different behavior when compared for isothermal and non-isothermal cases. For the present glass system the John-Mehl-Avrami model describes well the isothermal crystallization kinetics, while the Sestak-Berggren model is more suitable to describe the non-isothermal crystallization kinetics for glass-crystal transformation.

We have studied silver ion dynamics in mixed network former molybdophosphate glasses by varying the glass network formers ratio. We have shown that the macroscopic ion transport is correlated to the characteristic microscopic length scale and the modification of the phosphate network structure due to the introduction of molybdate network former. The time-temperature superposition of the conductivity spectra onto a single master curve is independent of the mixing of the network formers.

In this letter we have studied broadband conductivity spectra (10 Hz–3 GHz) of fast-ion-conducting silver selenite glasses of compositions xAgI-(1−x)(yAg2O-(1−y)SeO2). We have observed that the conductivity spectra below 10 MHz are characterized by a power law with exponent less than unity, while the conductivity spectra in the high-frequency range (above 10 MHz) have been adequately explained in the framework of the unified site relaxation model with exponent greater than unity. The scaling of the conductivity spectra indicates that the time-temperature superposition principle is valid in the low-frequency regime, but not in the high-frequency regime.

We have investigated the isothermal and non-isothermal crystallization kinetics in molecular glasses in the system Ag2O-SeO2-MoO3 with different modifier (Ag2O) contents. We have observed a change from two-dimensional to three-dimensional crystallization with the increase of the modifier content. We have shown that John-Mehl-Avrami and Sestak-Berggren models give the best description of the isothermal and non-isothermal crystallization kinetics respectively for the glass-crystal transformation.