Optical control of high-density alkali atom vapor in antirelaxation coated cells

Abstract In this work, we report on our investigations on LIAD (Light Induced Atomic Desorption) aimed at achieving high density of alkali atoms vapor in a coated cell at room temperature. The experimental results show the possibility to reach a density up to the limit when the medium becomes optically thick by applying highly efficient homogeneous illumination. The photon reabsorption mechanism prevents the precise evaluation of the density by measuring the absorption of a probe laser beam, but there is clear evidence that densities can be achieved higher by two orders of magnitude than the thermodynamic equilibrium value

Tunable and polarization-controlled high-contrast bright and dark coherent resonances in potassium

We demonstrate high-contrast electromagnetically induced absorption (EIA) bright resonances on the D1 line of K39 with characteristics comparable to those of the electromagnetically induced transparency (EIT) dark resonances observed in the same conditions. EIA is produced by the interaction of a weak probe beam with the atomic ground state driven in a degenerate coherent superposition by either a co- or counter-propagating pump beam. We have obtained an order of magnitude increase of the EIA's contrast with respect to previous similar experiments, performed with other alkalis, without compromising its linewidth. Furthermore, we show that the magneto-optic resonances can be continuously tuned from EIT to EIA by changing the relative handedness of circular polarizations of pump and probe beams, or depending on whether they co- or counter-propagate. This opens new perspectives in the use of EIA in a broad range of physical domains and in a large wealth of potential applications in optics and photonics

Ultrashort laser ablation of metals

The characterization of a plasma plume is a key issue in laser ablation and deposition studies. Combined diagnostic measurements by Optical Emission Spectroscopy, Fast Imaging have been used to study the dynamics and composition of laser ablation plume produced during ultrashort laser irradiation of metals, in vacuum. Our results show that, in the laser fluence range of 0.1-1.0 J/cm2, the process of matter removal results in a plasma plume which is mainly composed of two different populations: atoms and nanoparticles. The nanoparticles dynamics during expansion has been analyzed through their structureless continuum optical emission, while atomic species have been identified by their characteristic emission lines. The presence of a fast atomic component emitted from the sample surface as a result of the supercritical state induced by the intense ultrashort laser pulse irradiation has been also observed both by optical emission spectroscopy and fast imaging techniques. Finally, atomic force microscopy analysis of the material deposited at room temperature has allowed the characterization of the nanoparticles size distribution