Spectmchimica Acta. Vol. 48A, No. 1. pp. 19-24, 1992 Ptinted in Great Britain 05s48539/92 55.oo+o.al Pergamon Press plc zyxwvutsrqpon Time-resolved spectral investigations of laser light induced microplasma L. NANAI AND I. HEVESI JATE, Department of Experimental Physics, H-6720 Szeged, D6m t. 9, Hungary (Received 18 September 1990; accepted 17 December 1990) Abstract-The dynamical and spectral properties of an optical breakdown microplasma created by pulses of different lasers on surfaces of insulators (KCI), metals (Cu) and semiconductors (V,O,), have been investi- gated. Experiments were carried out in air and vacuum using different wavelengths @=0.694pm, type OGM-20,1= 1.06pm with a home-made laser based on neodymium glass crystal, and 1.= 10.6pm, similarly home-made) and pulse durations (Q-switched and free-running regimes). To follow the integral, dynamical and spectral characteristics of the luminous spot of microplasma we have used fast cameras (SFR-2M, IMACON-HADLAND), a high speed spectral camera (AGAT-2) and a spectrograph (ST%1). It has been shown that the microplasma consists of two parts: fast front (peak) with r=lOO ns and slow front (tail) with ~1~s durations. The detonation front speed is of the order of =ldcms-’ and follows the temporal dependence of p4. It depends on the composition of the surrounding gas and its pressure and could be connected with quick evaporation of the material investigated (peak) and optical breakdown of the ambient gaseous atmosphere (tail). From the delay in appearance of different characteristic spectral lines of the target material and its gaseous surrounding we have shown that the evolution of the microplasma involves evaporation and ionization of the atoms of the parent material followed by optical breakdown due to the incident and absorbed laser light, together with microplasma expansion. IT IS well known from different experimental observations that the laser light induced damage of materials is usually accompanied by the appearance of a luminous spark (optical breakdown) microplasma [l-8]. Investigation of the nature, spectral and dynamical properties of such a plasma has its own scientific and practical interest. It can provide useful information concerning the mechanism of material damage in different environments, as well as, possibly, helping to find appropriate treatments to enhance surface hardness and optical stability. EXPERIMENTAL The scheme of experimental set-up used is presented in Fig. 1. The light of a pulsed laser (1) was focused by means of an optical system (13) on the surface of different targets placed inside a vacuum chamber (11). Small fractions of the laser tight were --__--- n-n i-7 n -4-13 ti zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA 11 I\ I'\ 13 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA 1 I . . I I I 6 9 - I I Fig. 1. Scheme of experimental set up (details see in text). 19