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41.
Aluminum samples have been analyzed by femtosecond polarization-resolved laser-induced breakdown spectroscopy (fs-PRLIBS). We compare the obtained spectra with those obtained from nanosecond PRLIBS (ns-PRLIBS). The main specific features of fs-PRLIBS are that a lower plasma temperature leads to a low level of continuum and no species are detected from the ambient gas. Furthermore, signals obtained by fs-PRLIBS show a higher stability than those of ns-PRLIBS. However, more elements are detected in the ns-PRLIBS spectra. 相似文献
42.
The main characteristics of the third harmonic emission generated byfemtosecond laser pulses propagating in air are investigated by numericallysolving the coupled nonlinear Schr?dinger equations. Strong thirdharmonic emission is observed with a maximum conversion efficiency as highas 0.43%. The on-axis phase difference between fundamental beam and thirdharmonic is investigated. The result is in good agreement with thephase-locking mechanism. Dependence of the conversion of third harmonicemission on focusing conditions is also studied. The results are alsocompared with those of experiments. 相似文献