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We investigated the spatial and temporal evolution of temperature and electron density associated with femto- and nanosecond laser-produced plasmas (LPP) from brass under similar laser fluence conditions. For producing plasmas, brass targets were ablated in vacuum employing pulses either from a Ti:Sapphire ultrafast laser (40 fs, 800 nm) or from a Nd:YAG laser (6 ns, 1064 nm). Optical emission spectroscopy is used to infer the density and temperature of the plasmas. The electron density (ne) was estimated using Stark broadened profiles of isolated lines while the excitation temperature (Texc) was estimated using the Boltzmann plot method. At similar fluence levels, continuum and ion emission are dominant in ns LPP at early times (<50 ns) followed by atomic emission, while the fs LPP provided an atomic plume throughout its visible emission lifetime. Though both ns and fs laser-plasmas showed similar temperatures (∼1 eV), the fs LPP is found to be significantly denser at shorter distances from the target surface as well as at early phases of its evolution compared to ns LPP. Moreover, the spatial extension of the plume emission in the visible region along the target normal is larger for fs LPP in comparison with ns LPP.

We investigated the angular distribution of ions and atoms emanating from femto- and nanosecond laser-produced metal plasmas under similar laser fluence conditions. For producing plasmas, aluminum targets are ablated in vacuum employing pulses from a Ti:Sapphire ultrafast laser (40 fs, 800 nm) and an Nd:YAG laser (6 ns, 1064 nm). The angular distribution of ion emission as well as the kinetic energy distribution is characterized by a Faraday cup, while a quartz microbalance is used for evaluating deposited mass. The ion and deposited mass features showed that fs laser ablated plasmas produced higher kinetic energy and more mass per pulse than ns plumes over all angles. The ion flux and kinetic energy studies show fs laser plasmas produce narrower angular distribution while ns laser plasmas provide narrower energy distribution.

We investigated the laser wavelength effect on angular atomic and ionic emission from laser-produced Sn plasma, since it is regarded as a viable candidate for an EUV lithography source. For producing plasmas, the fundamental, second and fourth harmonics radiation from a Nd : YAG laser were used. The angular variation of atomic and ionic particle analysis was carried out using quartz crystal microbalance and Faraday cups by moving them in a circular path at a constant distance from the target normal. Along with atomic and ionic emission, we also compared the plasma emission features in the visible and EUV spectral regions. Results indicate strong forward bias in atomic and ionic plasma debris at all wavelengths. Shorter wavelength plasmas are found to generate more atomic particles while ion flux showed a similar trend irrespective of the excitation wavelength.

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