Emission enhancement in laser-induced breakdown spectroscopy from sample heating with a continuous-wave diode laser

In this work an affordable, energy-efficient technique to enhance the sensitivity of the laser-induced breakdown spectroscopy technique is presented. This method is based in applying the beam of a continuous wave (CW) diode laser into the spot where the focused beam of a pulsed Nd:YAG, high-power laser induces the plasma. With the present set-up the CW beam heats the sample's surface to 300 degrees C. It was found that pre-heating the target in this way increased the line intensity of both neutrals and ions by a factor of up to 4.5. It was also found that the plasma excitation temperature and the electron density of the heated sample did not differ significantly from those at room temperature. However the amount of ablated material did change significantly when the sample was heated, with the crater in the latter case as much as 8.9 times larger than that obtained at ambient temperature. We conclude that the intensification in the pre-heated-sample case stems not from increased electronic plasma density or temperature but rather from a larger plume size resulting from an increased amount of ablated material when the target is heated.