Fiber-coupled laser-induced breakdown and Raman spectroscopy for flexible sample characterization with depth profiling capabilities

A combined laser-induced breakdown spectroscopy (LIBS) and Raman spectroscopy system for depth profile analyses is presented. The systemincorporates a single 532 nmlaser source,which is delivered through an optical fiber to the sample site. The homogenized laser beam results inwell-defined cylindrical craterswith diameters of 100 μm. LIBS depth profiling analyses of metals was performed applying pulse energies of about 1 mJ. The application of up to 500 pulses allowed to drill through layers of several tens of microns, while observing sharp transitions at the layer interfaces. The capability of the system for Raman spectroscopy was investigated for various polymer samples by reducing the pulse energies belowthe respective ablation threshold. A combined Raman/LIBS depth profilingwas applied to a polymer-coatedmetal. Additionally, the capability of the system for calibration-free LIBS quantification (CF-LIBS) was evaluated. Quantification of major elements in metallic referencematerials showed good agreementwith the certified valueswith relative deviations of less than 30%. Finally, the optimized system was applied for depth profiling and elemental composition analysis of ancient Roman bronze rings. Overall, the presented setup combines the high flexibility of a fiber-coupled system with Raman andmicro-LIBS, making the systeminteresting for depth profiling and elemental quantification in archaeometric as well as industrial applications.