Nanosecond and femtosecond ablation of La0.6Ca0.4CoO3: a comparison between plume dynamics and composition of the films

Thin films of La0.6Ca0.4CoO3 were grown by pulsed laser ablation with nanosecond and femtosecond pulses. The films deposited with femtosecond pulses (248nm, 500fs pulse duration) exhibit a higher surface roughness and deficiency in the cobalt content compared to the films deposited with nanosecond pulses (248nm, 20ns pulse duration). The origin of these pronounced differences between the films grown by ns and fs ablation has been studied in detail by time-resolved optical emission spectroscopy and imaging. The plumes generated by nanosecond and femtosecond ablation were analyzed in vacuum and in a background pressure of 60 Pa of oxygen. The ns-induced plume in vacuum exhibits a spherical shape, while for femtosecond ablation the plume is more elongated along the expansion direction, but with similar velocities for ns and fs laser ablation. In the case of ablation in the background gas similar velocities of the plume species are observed for fs and ns laser ablation. The different film compositions are therefore not related to different kinetic energies and different distributions of various species in the plasma plume which has been identified as the origin of the deficiency of species for other material

Advances in multispectral and hyperspectral imaging for archaeology and art conservation

Multispectral imaging has been applied to the field of art conservation and art history since the early 1990s. It is attractive as a noninvasive imaging technique because it is fast and hence capable of imaging large areas of an object giving both spatial and spectral information. This paper gives an overview of the different instrumental designs, image processing techniques and various applications of multispectral and hyperspectral imaging to art conservation, art history and archaeology. Recent advances in the development of remote and versatile multispectral and hyperspectral imaging as well as techniques in pigment identification will be presented. Future prospects including combination of spectral imaging with other noninvasive imaging and analytical techniques will be discussed

Analysis of natural and artificial ultramarine blue pigments using laser induced breakdown and pulsed Raman spectroscopy, statistical analysis and light microscopy

http://www.sciencedirect.com/science/article/B6VNG-4V2NKN2-1/2/88334c7b5f21f6ac19eed9f3f8706b0

Pathways control in modification of solid surfaces induced by temporarily separated femtosecond laser pulses

International audienceReaction control by laser light is a unique method of the reaction dynamics mastery in the molecular chemistry. We provide evidence of phase control processing with femtosecond lasers in macroscopic solids. Rutile TiO2 monocrystals with (001) and (100) surface orientations were irradiated with repetitive pulses of femtosecond KrF laser of variable fluences and a temporal delay between two superimposed linearly polarized beams. The appearance of three types of surface morphology was thoroughly analyzed: low-spatial frequency laser-induced periodic surface structures (LSFL), grooves and unusual featureless flat area (FFA). The interaction of light with the excited surface led to the onset or suppression of the subwavelength LSFL, depending on whether the temporal delay between laser beams is larger or smaller than the critical value of ~6 ps. By contrast, the suprawavelength grooves and FFA appeared at longer temporal delays. A strong decrease of the grooves onset energy was observed on the (001) oriented crystal after the delay of ~8 ps; the decrease of onset energy was also observed on the (100) oriented crystal, where FFA appeared instead of grooves. The critical delay is discussed in framework of a phenomenological model describing the energy evolution of excited transient states along the "reaction" coordinate