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The emission spectrum produced by a Nd:YAG laser irradiation of pure cadmium target is investigated. Results reveal that at lower pressure, less than 25 mbars, the signal to noise ratio (SNR) is smaller and increases with the air pressure.

We present optical emission studies of the laser ablation brass plasma generated by the fundamental, second, and third harmonics of a neodymium doped yttrium aluminum garnet laser. The spectra predominantly reveal the spectral lines of the neutral and singly ionized copper and zinc. The excitation temperatures are determined by the Boltzmann plot method, whereas the electron number densities have been extracted from the Stark broadened line profiles. The spatial variations in the spectral line intensities and the plasma parameters at 1000, 500, and 100 mbar air pressures have been evaluated. Besides, the effect of the ambient gases (He, Ne, and Ar), the laser irradiance, and the laser wavelengths on the plasma parameters have been investigated. [ABSTRACT FROM AUTHOR]

Optical emission spectroscopy is used to characterize the laser-produced strontium plasma by using the fundamental, second, and third harmonics of a Nd:YAG laser. Variations in the electron temperature (Te) and number density (Ne) as a function of distance, laser irradiance, and ambient gas pressure have been studied by using the emission lines of neutral strontium. In addition, absorption mechanisms responsible for the variation of the electron temperature and number density and the dependence of the spectral line intensities on the ambient gas pressure and laser irradiance are discussed. [ABSTRACT FROM AUTHOR]

Spectroscopic methods are used for examining the temporal and spatial evolution of electron temperature and electron density from Sn plasma produced by a C[O.sub.2] laser in vacuum. The results have shown that the electron temperature and density from Sn plasma produced by a C[O.sub.2] laser with wavelength of 10.6 [micro]m is lower than the previous results by using a 1064 nm laser in a similar parameter regime.

The various effects of the laser wavelength on the charge state resolved ion energy distributions obtained from the laser-induced sn plasma are determined. The laser wavelength is shown to be dependent on the laser energy absorption, which is found to lead to the differences in the ion energy distributions.

The interaction of a CO2 laser pulse with Sn-based plasma for a 13.5-nm extreme ultraviolet (EUV) lithography source was investigated. It was noted that a CO2 laser with wavelength of 10.6 µm is more sensitive to surface impurities as compared with a Nd:YAG laser with wavelength of 1.06 µm. This reveals that a CO2 laser is more likely absorbed in a thinner layer near the target surface. Compared with a Nd:YAG laser, a CO2 laser shows higher in-band (2% bandwidth) conversion efficiency (CE) with a solid Sn target due to less reabsorption of the EUV emission induced by the plasma. However, with foam targets containing low concentrations of Sn, the in-band CE is lower than that with solid Sn. The CE can be enhanced with plasma confinement. These results suggest that a driving laser with wavelength between 1.06 and 10.6 µm may be an even better choice to generate higher CE from laser to 13.5-nm EUV emission. [ABSTRACT FROM AUTHOR]