飞秒激光诱导钛表面形成高空间频率周期条纹结构

High-spatial frequency periodic structures induced on Ti surface by femtosecond laser pulses

利用波长为800nm的飞秒激光,在空气和去离子水中诱导钛表面形成不同的周期条纹结构。在空气中,激光能量密度为0.265J/cm^2时,钛表面主要形成周期为500~560nm低空间频率条纹结构;激光能量密度为0.102J/cm^2时,主要形成的是周期为220~340nm高空间频率条纹结构。两种条纹均垂直于入射激光偏振方向,且条纹周期随着脉冲重叠数的增大而增大。在水中,除形成垂直激光偏振方向、周期为215~250nm的高空间频率条纹结构,还形成了平行于激光偏振方向且周期约为入射激光波长八分之一的高空间频率条纹结构。利用表面等离子体理论、二次谐波及Sipe理论对各种周期条纹结构的形成机理进行分析,发现周期条纹结构的形成与钛表面氧化层有密切的关系。

This paper reports the formation of different periodic structures on Ti surface irradiated by 800 nm femtosecond laser pulses in air and water. In air, low spatial frequency periodic structures with period of 500-560 nm are obtained with high la- ser fluence irradiation; high spatial frequency periodic structures with period of 220-340 nm are obtained with low laser fluence ir- radiation. All of them are perpendicular to the laser polarization and the period of the structures increases with pulse numbers. In water, not only high spatial frequency periodic structures （215-250 nm） with direction perpendicular to the laser polarization are obtained, but also high spatial frequency periodic structures （about one eighth of laser wavelength） with direction parallel to the laser polarization are obtained. Combined with the surface plasmon polaritons, second harmonic generation and the Sipe model to interpret different periodic structures＇ formation mechanism, we found that the formation of periodic structures is related to the titanium oxide layer.