Spectroscopic Studies of Indium Plasma Produced by Fundamental (1,064 nm) and Second (532 nm) Harmonics of an Nd:YAG Laser

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In this paper, we present spectroscopic studies of a laser-induced indium (In) plasma produced by fundamental (1,064 nm) and second (532 nm) harmonics of an Nd:YAG laser along with the characteristics determined by plasma parameters. The electron temperature is determined using four lines of neutral indium at 260.17, 271.02, 275.38, and 325.85 nm, in view of the Boltzmann plot method. The temperature varies from 6,470 K at 0.05 nm to 4,990 K at about 2 mm from the target surface for the fundamental wavelength and from 6,250 to 4,880 K for the second harmonic. The electron density is ±300 calculated using the Stark broadened profiles recorded at laser pulse energy 130 mJ (for fundamental) and 72 mJ (for second harmonic) as 5:8·10¹⁶ and 6:9·10¹⁶ cm⁻³, respectively. These values decrease to 3:5·10¹⁵ and 4:9·10¹⁵ over a distance of 2 mm from the target surface, respectively. Moreover, we study the variation of N_e as a function of laser irradiance as well as its spatial variation from the target surface.