Research lines

Laser ablation plasmas are complex media characterized by varying degrees of ionization and non-equilibrium states, and their compositional and dynamic analysis is often far from trivial. In our labs at IQFR, we rely on a range of techniques aimed at the description and understanding of these systems:

a) Detection and mass selection of the ionic content of the plasma. The target is placed in the extraction region of a time-of-flight mass spectrometer equipped with a multi-channel plate detector. This system allows the detection and distinction of species of up to 5000 a.m.u.

Mass spectra showing the ionic content of a laser ablation plasma of CdS upon 532-nm laser ablation.


b) Detection of the neutral composition of the plasma. In this case a sophistication of the above technique must be used, where a second (post-ionization) laser is used to remove electrons from the neutral species in the plasma. Typically, ArF (193 nm) or fluorine (157 nm) lasers are used for this purpose.


c) Detection of spatially-resolved spontaneous emissions. The measurement of the images of the global luminous radiation emitted in the visible region by excited species in the plasma, when acquired with a shutter speed that is fast enough compared with the plasma dynamics, provides important information of the compositional components of the medium, their speed and their angular distribution. These experiments are conducted by forming the image of the plasma on a spectrometer used in zeroth diffraction order and detecting the image on a temporally gated ICCD.

Images of a Cu laser ablation plasma acquired with shutter speeds of 50 ns, as a function of the delay of the image acquisition with respect to the ablation event. Two compositional components are obvious in this case.


d) Detection of spectrally and spatially resolved spontaneous emissions. Additional information can be gained by spectrally resolving spontaneous fluorescent emissions from species in the plasma. Experiments are conducted similarly to the previous case, except that the spectrometer is used in first diffraction order.

Spectrally and spatially resolved optical emissions from a CdS laser ablation plasma for a narrow 20 ns temporal window that opens at 100 ns delay with respect to the ablation event.