Atom-light interaction in nano-structured alkali-metal vapour cells

Abstract

We present an experimental and theoretical study into the behaviour of thermal atoms confined to bespoke micro- and nano-structured vapour cells. We detail advancements to our cell platform, and use our cells to study a number of physical effects at novel lengthscales. We study light-induced atomic desorption (LIAD) for localised liberation of wall-adsorbed atoms into the vapour phase, and demonstrate density increases of up to 5× in a micron-scale region. We also find that non-resonant laser light can create high density condensed regions of rubidium on the cell walls. We demonstrate two-colour excitation and fluorescence spectroscopy in a nano-cell, and use this scheme to measure the density distribution of atoms confined to a 1 × 1 µm channel. We measure an exponential decay with distance into the channel, with a lengthscale of 4.0(11) µm. Finally, we study the response of confined vapours to resonant nanosecond laser pulses. We measure the decay time of the fluorescence activity from single-colour excitation to the 5P3/2 to be much less than the natural lifetime, which we conclude to be due to atomic time of flight. We also perform pulsed excitation to the 5D5/2 state using a two-colour scheme in various geometries, and produce a Monte Carlo wavefunction simulation to model this. We conclude that, in this case involving the longer lived 5D5/2 state, velocity selectivity and time of flight both impact the measured timescale, and use our simulations to extract the contributing velocity classes. Due to the selectivity imposed by our cells, we measure a decay timescale of 38.71(13) ns in a 1 µm cell, despite the mean atomic time of flight being only approx. 3 ns. We discuss the implications of our results in the context of both fundamental physics and technological applications throughout.