Polarization Resolved Laser-Induced Breakdown Spectroscopy of Al

Abstract

It is shown that the continuous background of the laser-induced breakdown spectrum of Al produced by 800 nm femtosecond pulses is strongly polarized. Use of a polarizer to filter out the background significantly improves the signal/noise and signal/background ratios of the discrete line spectrum. The effects of the laser pulse energy, focal position, incidence and detection angles, and the polarization plane of the laser were investigated. Polarization resolved laser-induced breakdown spectroscopy (PRLIBS) is much less sensitive to these variables than conventional, ungated fs-LIBS, making this a much more versatile analytical tool. These measurements reveal qualitatively different mechanisms for the continuous and discrete parts of the spectrum.

Calibration Methods of Laser-Induced Breakdown Spectroscopy

“…Another way to deduct a continuous background is to add a polarizer to the collected light path. Penczak et al's [26] research results show that the continuous background of the Al plasma emission spectra induced by 800 nm femtosecond pulse laser is strongly polarized. The use of a polarizer can effectively filter the continuous spectrum, thus improving the signal-to-noise ratio and the signal-to-back ratio of the characteristic spectrum.…”

Polarization and fluence dependence of the polarized emission in nanosecond laser-induced breakdown spectroscopy

“…7 of Ref. [3]). We also found that the laser-induced breakdown spectrum (LIBS) of air is likewise unpolarized (unpublished data associated with Ref.…”

“…Light emitted by the excited material can provide valuable information about the ablation mechanism as well as a powerful tool for analyzing the elemental composition of the substrate. A number of studies have shown that the light emitted from laser-induced plasmas, especially the continuum radiation, can be strongly polarized [1][2][3][4][5]. This effect was observed for a wide variety of solid materials and for both nanosecond and femtosecond excitation.…”

Comparison of the polarisation of line and continuum emission in a laser produced plasma

“…The technique of PPS has been applied to laser produced plasmas where partial polarisation has been observed in the x-ray and visible spectral ranges [2,3]. Importantly, a particular application of PPS known as polarisation-resolved laser induced breakdown spectroscopy (PRLIBS) exploits this partial polarisation in order to enhance the signal to background ratio over traditional LIBS measurements [4]. In various wide-ranging studies [4][5][6], it was shown that the continuum radiation tends to have a greater degree of polarisation than the line emission.…”

“…Importantly, a particular application of PPS known as polarisation-resolved laser induced breakdown spectroscopy (PRLIBS) exploits this partial polarisation in order to enhance the signal to background ratio over traditional LIBS measurements [4]. In various wide-ranging studies [4][5][6], it was shown that the continuum radiation tends to have a greater degree of polarisation than the line emission. For this reason, placing a polariser in front of a spectrometer results in lower background continuum, thus increasing the signal-background ratio which is a figure of merit for LIBS.…”