Continuous modulations of femtosecond laser-induced periodic surface structures and scanned line-widths on silicon by polarization changes

Abstract

Large-area, uniform laser-induced periodic surface structures (LIPSS) are of wide potential industry applications. The continuity and processing precision of LIPSS are mainly determined by the scanning intervals of adjacent scanning lines. Therefore, continuous modulations of LIPSS and scanned line-widths within one laser scanning pass are of great significance. This study proposes that by varying the laser (800 nm, 50 fs, 1 kHz) polarization direction, LIPSS and the scanned line-widths on a silicon (111) surface can be continuously modulated with high precision. It shows that the scanned line-width reaches the maximum when the polarization direction is perpendicular to the scanning direction. As an application example, the experiments show large-area, uniform LIPSS can be fabricated by controlling the scanning intervals based on the one-pass scanned linewidths. The simulation shows that the initially formed LIPSS structures induce directional surface plasmon polaritons (SPP) scattering along the laser polarization direction, which strengthens the subsequently anisotropic LIPSS fabrication. The simulation results are in good agreement with the experiments, which both support the conclusions of continuous modulations of the LIPSS and scanned line-widths.

Nanosecond laser pulse induced concentric surface structures on SiO_2 layer

“…The characteristics of the structures, also referred to as ripples, are depended on the material properties and the irradiation conditions, such as wavelength, laser polarization, laser fluence, pulse duration, incident angle and number of the laser pulse irradiation [2,3]. Many researchers have devoted themselves to observing and understanding the structures induced by femtosecond (fs) and nanosecond (ns) lasers.…”

Femtosecond laser induced tunable surface transformations on (111) Si aided by square grids diffraction

“…Meanwhile, no anisotropic ablation phenomenon under linearly polarized fs laser irradiation is found on the surface of (111) Si. 18,28 An anisotropic formation of ripples based on the crystal orientations has been found on the surface of (100) Si with cubic crystal structure due to the direction dependence of the effective mass of electron. 28 Here, the aided square grid can be seen as an additional quasi-cubic crystal structure added to the (111) Si surface.…”

“…1) is similar to that in our previous studies. 18 The fs laser pulse (1 kHz, s ¼ 50 fs (FWHM), and k ¼ 800 nm) travels through the dichroic mirror (DM) and is focused through an achromatic doublet (f ¼ 100 mm) on the surface of standard one-side-polished ptype (111) Si chip (10 mm  10 mm  1 mm). The focus point is set on the surface by moving the sample along the zdirection until the damage on the surface is most severe.…”

“…Directional SPP scattering along the polarization direction by the initially formed ripple structures can be achieved under linearly polarized fs laser irradiation. 18 Meanwhile, the intrinsic TM state of the SPP field leads to a TM incidence for the SPP launching. Thus, the SPP launching and coupling is perpendicular to the ripple structures (see Fig.…”

“…An elliptical shape of the ripple structure along the polarization direction can be achieved under linearly polarized fs laser irradiation. 18 Reduce the scanning speed, the increased laser energy leads to the reduction of the distance between the two adjacent ripple dots. Thus, the orthogonal periodic ripple dots with the minimum adjacent spacing are apt to be connected to stripe ripple lines when the polarization direction is near the horizontal or vertical directions.…”