In this study, we report the formation of laser-induced periodic surface nanometric concentric ring structures on silicon surfaces through single-spot irradiation with orthogonally polarized femtosecond laser double-pulse sequences (OP pulses). The period of the ring structures is marginally smaller than the irradiated laser’s wavelength, which indicates that the structures are a type of low-spatial-frequency laser-induced periodic surface structures. Regular nanometric concentric ring structures can be formed when the time delay between two subpulses is approximately 1 ps (roughly from 500 fs to 1.5 ps) and the number of laser bursts is approximately 4. The formation mechanism of the concentric ring structures is attributed to the surface wave (i.e., cylindrical wave) stimulated by OP pulses through single-spot irradiation is radially distributed. Large area of concentric ring structures eliminating anisotropy in the generation of structural colors was shown in this paper.

中文翻译：

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正交极化飞秒激光双脉冲序列单点辐照在硅表面形成激光诱导的周期表面纳米同心环结构

在这项研究中，我们报告了通过正交偏振飞秒激光双脉冲序列（OP脉冲）的单点照射在硅表面形成激光诱导的周期表面纳米同心环结构。环形结构的周期略小于照射激光的波长，这表明该结构是低空间频率激光诱导的周期性表面结构的一种。当两个子脉冲之间的时间延迟大约为1 ps（大约从500 fs到1.5 ps）并且激光脉冲的数量大约为4时，可以形成规则的纳米同心环结构。同心环结构的形成机理归因于由OP脉冲通过单点照射激发的表面波（即圆柱波）呈放射状分布。