Near-threshold femtosecond laser fabrication of one-dimensional subwavelength nanogratings on a graphite surface
Near-threshold femtosecond laser fabrication of one-dimensional subwavelength nanogratings on a graphite surface
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DOI：
10.1103/physrevb.83.115426
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发表时间：
2011-03-14
影响因子：
3.7
通讯作者：
Sharipov, A. R.
中科院分区：
文献类型：
--
作者：
Golosov, E. V.;Ionin, A. A.;Sharipov, A. R.
在环境空气中的准单晶石墨的平面上进行多次近阈值激光照射后，制备了具有多个周期 Lambda 近似于 110-800 nm 远低于或相当于 744 nm 泵浦激光波长的叠加一维准周期光栅，并且脊方向垂直于红外飞秒激光脉冲的线性偏振。光栅周期的宽范围对应于最终纳米浮雕的大量空间傅里叶谐波（高达 m = 7 阶，Lambda(m) 近似于 800 nm/m = 110-800 nm），定性地表示激光诱导的中间表面浮雕的非正弦轮廓（一组周期性的、宽间隔的窄纳米沟槽），它提供了入射飞秒激光脉冲的相应多角度衍射。光激发石墨瞬态光学常数的实验测量和建模证明，在第一阶段，光激发初始平面石墨表面上的一阶（Lambda（1）近似于800 nm）表面等离子体激元极化（SPP）波通过光生成致密电子空穴等离子体（类似于10（21）cm（-3））变成金属。这种SPP波通过其与入射激光波的干涉以非正弦表面光栅的形式提供中间纳米浮雕，从而在近阈值激光照射条件下在干涉最大值处导致材料的高度局部表面烧蚀。在下一阶段，通过多个入射激光脉冲在中间非正弦表面光栅上的多角度衍射，形成多周期亚波长纳米光栅。
Superimposed one-dimensional quasiperiodic gratings with multiple periods Lambda approximate to 110-800 nm well below or comparable to the pump laser wavelength of 744 nm, and ridge orientations perpendicular to the linear polarization of infrared femtosecond laser pulses, were fabricated after multiple near-threshold laser shots on a planar surface of quasimonocrystalline graphite in ambient air. The broad range of the grating periods corresponds to the large number of spatial Fourier harmonics of the final nanorelief (up to m = 7th order, Lambda(m) approximate to 800 nm/m = 110-800 nm), qualitatively representing the nonsinusoidal profile of the laser-induced intermediate surface relief (the set of periodic, broadly spaced narrow nanotrenches), which provides the corresponding multiangle diffraction of the incident femtosecond laser pulses. Experimental measurements and modeling of the transient optical constants of the photoexcited graphite justify the excitation, at the first stage, of the first-order (Lambda(1) approximate to 800 nm) surface plasmon-polaritonic (SPP) wave on the photo-excited initial planar graphite surface becoming metallic via photo-generation of dense electron hole plasma (similar to 10(21) cm(-3)). Such an SPP wave provides intermediate nanorelief in the form of the nonsinusoidal surface grating via its interference with the incident laser wave, resulting under near-threshold laser irradiation conditions in the highly localized surface ablation of the material in the interference maxima. During the next stage, the multiperiod subwavelength nanogratings develop through the multiangle diffraction of the multiple incident laser pulses on the intermediate nonsinusoidal surface grating.