DOUBLE-PULSE LASER-INDUCED BREAKDOWN SPECTROSCOPY WITH 1030 AND 257.5 nm WAVELENGTH FEMTOSECOND LASER PULSES

Double-pulse laser-induced breakdown spectroscopy (DP-LIBS) studies and the comparison with the single-pulse experiments were performed on the steel sample. Two harmonics of the femtosecond Yb:KGW laser at 1030 and 257.5 nm were combined in the collinear beam geometry to carry out double-pulse LIBS experiments at atmospheric pressure in air. The influence of the delay between the two (NIR pulse was delayed in regard to UV pulse) laser pulses on the LIBS signal intensity was investigated. The inter-pulse delay times were in the range from 0 to 200 Ps. In the delay range from 0 to 40 ps the LIBS plasma emission intensity increased steadily and in the range from 40 to 200 ps (maximum inter-pulse delay investigated) the plasma lines' emission intensity remained almost constant. LIBS signal intensity increased 3-5 times in comparison with the single pulse case when an optimum inter-pulse delay between the two ablating pulses was used.