Nanosecond polarization-resolved laser-induced breakdown spectroscopy

Abstract

It is shown that the continuum emission produced in the ablation of an Al target with nanosecond laser pulses is much more strongly polarized than the discrete line emission. This effect may be utilized to improve the resolution of the laser-induced breakdown spectroscopy spectrum by using a polarizer to filter out the continuum background. The effects of laser fluence and focal position are also reported. It is further shown that the lifetime of the emission closely tracks the intensity spectrum.

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

“…2 shows emission (LIBS) and polarization spectra over the range of 385-505 nm taken with a fluence of 13.2 J/cm 2 . These spectra are similar to our previous work [4] as well as that of Majd et al Specifically, the polarization of the continuum radiation varies slowly with wavelength in this spectral region. The strong Al lines near 400 nm in the LIBS spectrum appear as windows in the polarization spectrum, indicating that the polarization of the discrete emission is smaller than that of the continuum emission.…”

“…At an angle of incidence of 30 o , the difference in the Fresnel reflection efficiencies of s-and p-polarization are small and could give rise to P b 10%. While this effect may explain the small polarizations seen in the experiment of Asgill et al, it cannot account for the very large polarizations seen in previous experiments [1][2][3][4][5], ranging from 20% to almost complete (P = 100%) polarization.…”

“…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.…”

High-speed two-frame shadowgraphy for velocity measurements of laser-induced plasma and shock-wave evolution

“…The methods used in the characterization of laserinduced plasma and shock waves include different optical techniques, such as shadow and streak photography [8][9][10][11], holography [12], laser-beam-deflection probe [13], interferometry [14], and laser-induced spectroscopy [15,16]. Since the plasma and ablative shocks are short, transient phenomena that exhibit significant pulse-topulse variations, there is a special interest in methods that provide their spatially and temporally resolved characterization [17].…”

Fraunhofer-type absorption line splitting and polarization in confocal double-pulse laser induced plasma

“…In several studies [19][20][21][22][23][24], strong polarization of LIP emission was reported for many materials. More recently, it was found that this effect is caused by Fresnel polarization of the reflected light rather than by an anisotropic electron velocity distribution [25].…”