Laser Spectroscopy and Sensing

Enhancement of Plasma Emission by Mid-IR Heating

We are investigating dual-pulsed laser induced breakdown spectroscopy (LIBS) using both an Nd:YAG laser at fundamental wavelength of 1064 nm and TEA CO2 laser a 10.6 µm as a possible method of improving the sensitivity of this analytical technique. We have chosen to use a CO2 laser because more absorption of laser energy should be possible as a result of the critical electron density scaling with the square of the laser wavelength and therefore. To quantify any effect of this additional longer wavelength pulse, we have looked at metal samples to investigate the thermodynamic properties of the laser induced plasma. For an iron sample, we found little plasma heating resulting from a CO2 pulse following the ablation pulse of the Nd:YAG laser; however, there was an increase in plasma temperature and spectral emission when the CO2laser pulse preceded the Nd:YAG.

Recently, our work has focused on few-micron-thick films of organic material on silicon substrates. For these samples, the enhanced plasma emission resulted from an ablative pulse from the Nd:YAG followed by a re-heating pulse from the CO2 laser.