Laser-Induced Breakdown Spectra in the Infrared Region from 750 to 2000 nm Using a Cooled InGaAs Diode Array Detector

Emissions from a laser-induced breakdown spectroscopy (LIBS) plasma were examined in the region from 750 nm to 2000 nm. A Nd:YAG laser at 532 nm and 75 mJ per pulse were used to initiate the plasma. The detector was an InGaAs 1024 element diode array cooled to −100 °C. An f/4 spectrometer with gratings blazed for this region was used as the dispersive element. Survey spectra of soils, uranium, and other selected samples were taken in air and in a flow cell purged with argon at a local pressure of 0.84 × 10⁵ Pa. Strong infrared lines of neutral aluminum, carbon, potassium, silicon, sulfur, and uranium, as well as once ionized lines of calcium, were observed out to 1670 nm. For potassium, the detection limits of the infrared (IR) system were compared with those obtained from a standard intensified charge-coupled device (ICCD) spectrometer arrangement, using the 766–770 nm doublet. Detection limits with the IR system were twice as high as those obtained from the ICCD detector.