Observation of near total polarization in the ultrafast laser ablation of Si

Abstract

We report nearly completely polarized emission from the plasma produced in the femtosecond ablation of Si(111). Pairs of ultrashort laser pulses were focused onto the target in air, and the polarization spectrum was measured as a function of energy, pulse delay, and polarization state of the laser. When the laser was focused on the surface, the fluorescence continuum was strongly polarized, whereas discrete lines appeared as minima in the polarization spectrum. Under this focusing condition, the continuum polarization increased with pulse delay and decreased with pulse energy and fluorescence wavelength, with >95% polarization in the ultraviolet.

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

“…1 suggests that these factors do not play a primary role in the polarization mechanism. Corroborating evidence is provided by our femtosecond experiments, in which we observed high values of P for silicon [1], copper [2] and graphite [2] at 800 nm. The insensitivity to material and wavelength (but not necessarily to pulse duration) suggests that the polarization depends more on the properties of the plasma than of the underlying substrate.…”

“…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.…”

Double pulse ultrafast laser ablation of nickel in vacuum

“…[1][2][3][4] Double pulse ͑DP͒ irradiation has been also used in experiments aiming to elucidate the ablation mechanisms, or to modify the properties of the ablated species. 5,6 Most of these studies deal with ULA of a silicon ͑Si͒ target, while DP ULA of metals has been less investigated.…”

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].…”