Zhao Zhen, Xia Chaoqun, Yang Jianjun
GPL Photonics Laboratory, State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China.
Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China.
Nanomaterials (Basel). 2021 Sep 14;11(9):2389. doi: 10.3390/nano11092389.
We report the formation of a sole long nanowire structure and the regular nanowire arrays inside a groove on the surface of Fe-based metallic glass upon irradiation of two temporally delayed femtosecond lasers with the identical linear polarization parallel and perpendicular to the groove, respectively. The regular structure formation can be well observed within the delay time of 20 ps for a given total laser fluence of = 30 mJ/cm and within a total laser fluence range of = 30-42 mJ/cm for a given delay time of 5 ps. The structural features, including the unit width and distribution period, are measured on a one-hundred nanometer scale, much less than the incident laser wavelength of 800 nm. The degree of structure regularity sharply contrasts with traditional observations. To comprehensively understand such phenomena, we propose a new physical model by considering the spin angular momentum of surface plasmon and its enhanced inhomogeneous magnetization for the ferromagnetic metal. Therefore, an intensive TE polarized magnetic surface wave is excited to result in the nanometer-scaled energy fringes and the ablative troughs. The theory is further verified by the observation of nanowire structure disappearance at the larger time delays of two laser pulses.
我们报道了在铁基金属玻璃表面的凹槽内，当分别用两个具有相同线性偏振且平行和垂直于凹槽的时间延迟飞秒激光照射时，形成了单一的长纳米线结构和规则的纳米线阵列。对于给定的总激光能量密度(\varPhi = 30) (mJ/cm^2)，在20皮秒的延迟时间内可以很好地观察到规则结构的形成；对于给定的5皮秒延迟时间，在总激光能量密度范围(\varPhi = 30 - 42) (mJ/cm^2)内也能观察到。包括单元宽度和分布周期在内的结构特征是在一百纳米尺度上测量的，远小于800纳米的入射激光波长。结构规则程度与传统观察结果形成鲜明对比。为了全面理解此类现象，我们通过考虑表面等离子体的自旋角动量及其对铁磁金属增强的非均匀磁化，提出了一个新的物理模型。因此，激发了强烈的TE偏振磁表面波，导致了纳米尺度的能量条纹和烧蚀凹槽。通过观察两个激光脉冲在较大时间延迟时纳米线结构的消失，进一步验证了该理论。
