Laser-Induced Breakdown Spectroscopy (LIBS) Analysis of Laser Processing in Active Crystal with Nanosecond Laser Pulses

摘要

Laser-induced breakdown spectroscopy (LIBS) analysis is applied to study the ablation threshold and the main plasma features of active crystals used for laser processing with Nd~(3+) ions. The experiments were conducted by using nanosecond laser pulses from a neodymium-doped yttrium aluminum garnet (Nd : YAG) laser and its harmonics. In particular, we have studied the ablation process in SBN, strontium barium niobate (Sr_xBa_(1-x)Nb_2O_6, x=0.6), and SBN, sodium barium niobate (Ba_2NaNb_5O_(15)), nonlinear and ferroelectric crystals. Two different ablation regimes have been identified by LIBS analysis with high sensitivity compared with the standard method of hole-diameter measurement. Analyzing spectroscopically the plasma emission, we have found a particular behavior with the excitation wavelength. For example, the electronic density and temperature in SBN-generated plasmas present an abnormal behavior with the excitation wavelength. We therefore conclude that the energy gap corresponding to these crystals plays an important role in describing this fact. Hence, the resonant ablation in doped crystals can be a suitable point for exploration in further works in order to use the plasma performances to optimize the laser processing by nanosecond pulses for technological applications.