Light induced desorption and diffusion of alkali atoms in porous glasses

Year: 2005

Authors: Burchianti A., Marinelli C., Bogi A., Mariotti E., Biancalana V., Veronesi S., Moi L., Delta Valle F.

Autors Affiliation: Universit di Siena, Dipartimento di Fisica, Italy; Universit di Trieste, Dipartimento di Fisica, Italy

Abstract: Light induced atomic desorption (LIAD) of alkali metals in dielectric media is an interesting field of investigation for the study of atom-solid interactions as well as for applications. Huge light-induced atom desorption have been recently observed from siloxane and paraffin films. The LIAD effect proves extremely useful to realize light-controlled atomic sources. In particular we have developed a new method, based on LIAD, to feed atoms in a vapour-cell magneto-optical trap that allows a significant improvement in the loading rate [1]. Recently we also reported non-thermal photo-ejection of alkalis embedded in porous silica [2]. This material has a huge internal effective surface. During the preparation of the samples, part of the glass mass is removed leaving narrow pores and tunnels where the atoms can be adsorbed. The photodesorption occurs when a porous glass sample, previously exposed to alkali vapour, is illuminated either with ordinary or laser light and it is obtained even with power density weaker than one mW/cm2. Different porous glass samples placed inside sealed cells containing Rb or Cs were exposed to laser light of various intensities and frequencies. The desorbing rate and the maximum increase of the vapour density were measured for different pore size diameters and compared with those obtained in pyrex cells coated with organic films. The dynamical evolution of the process was analysed, showing difference features as a function of the intensity and frequency of the desorbing light. This signature of desorption process can be attributed to diffusive mechanisms, controlled by light, driving the atomic transport inside the glass matrix. This work suggests that porous silica can be used as extremely compact Light Controlled Atom Dispensers (LICAD). Indeed atomic sources made with porous glass are clean systems: they do not demand any heating of the system and do not make the experimental design more complicated. All these characteristics make such alkali dispensers suitable to be integrated with microscale devices for atom manipulation as atom-chips based on BEC. In addition these systems open interesting perspectives both for the study of atoms confined in micro and nano sized dielectric structures and for the development of new quantum optics sensors.

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KeyWords: Alkali atoms; Atomic sources; Atomic transport; Light induced atomic desorption (LIAD), Density of gases; Desorption; Diffusion; Glass; Laser optics; Magnetooptical effects; Paraffin oils; Quantum optics, Alkali metals
DOI: 10.1109/EQEC.2005.1567384