Wavefront-enhanced laser-induced breakdown spectroscopy (WELIBS) with lasers at multi-wavelengths via crystalline quartz†

Abstract

The current work proposes developing the wavefront-enhanced laser-induced-breakdown spectroscopy (WELIBS) approach using a crystalline quartz slide instead of the crystalline silicon wafer. Such substitution widens the application of WELIBS in the UV, visible, and IR laser wavelength ranges, not only the IR, as in the case of the silicon wafer. A Shack–Hartmann wavefront sensor (SHWFS) has been used to prove the capability of the crystalline quartz slide to convert the wavefront shape from quasi-Gaussian to a flat-top one in different ranges of wavelengths. The analytical performance of the novel WELIBS arrangement with the crystalline quartz slide has been studied using a pure zinc target, which showed a pronounced enhancement in the intensity of the spectral lines (two to sixfold) compared to the conventional LIBS technique for the three laser wavelengths the IR (1064 nm), the green (532 nm), and the UV (355 nm). Furthermore, seven certified bronze alloy samples have been used to study the achieved analytical improvement of the novel WELIBS analytical performance by testing its capability of estimating the limit of detection (LOD) of different minor elements. From the WELIBS and LIBS spectra of the bronze alloys, calibration lines of Zn, Sn, and Pb have been plotted to estimate the limit of detection for each element. The LOD for WELIBS was half that of LIBS. WELIBS with the quartz slide for beam shaping is superior to WELIBS with the Si wafer since it can be used with different laser wavelengths and not only the IR and provides similar, or better, analytical enhancement than the conventional LIBS.