Wan Hui, Yu Shengtao, Lei Yu, Zhao Qiang, Tao Guoyi, Luan Shiyi, Gui Chengqun, Zhou Shengjun
Appl Opt. 2021 Apr 1;60(10):2783-2787. doi: 10.1364/AO.418239.
Improving photothermal efficiency can reduce the melting threshold of metal nanowires. The photothermal efficiency of a polarized laser to Cu nanowires was investigated by numerical simulation and experiment. Our simulation results reveal that the photothermal efficiency of a polarized laser depends on the intensity and distribution area of surface plasmons excited by the laser. As the angle between the polarization direction of the incident laser and the long axis of the Cu nanowire increases, the laser-excited surface plasmons shift from both ends to the sidewall of the Cu nanowire. Such a distribution of surface plasmons was confirmed by the melting behavior of Cu nanowires irradiated by a 450 nm polarized laser. Increasing the laser wavelength will enhance the intensity of the surface plasmons but reduce the distribution area of the surface plasmons. As a result, a higher photothermal efficiency was achieved using a laser with a polarization direction perpendicular to the long axis of the Cu nanowire and a wavelength less than 550 nm. Due to the higher photothermal efficiency, the melting threshold of Cu nanowire irradiated by a laser with polarization perpendicular to the long axis of the Cu nanowire is 32 mW, which is around 20% lower that of Cu nanowire irradiated by a laser with polarization parallel to the long axis of the Cu nanowire.
提高光热效率可以降低金属纳米线的熔化阈值。通过数值模拟和实验研究了偏振激光对铜纳米线的光热效率。我们的模拟结果表明，偏振激光的光热效率取决于激光激发的表面等离子体激元的强度和分布面积。随着入射激光偏振方向与铜纳米线长轴之间的夹角增大，激光激发的表面等离子体激元从铜纳米线的两端向侧壁移动。通过450 nm偏振激光照射铜纳米线的熔化行为证实了这种表面等离子体激元的分布。增加激光波长会增强表面等离子体激元的强度，但会减小表面等离子体激元的分布面积。因此，使用偏振方向垂直于铜纳米线长轴且波长小于550 nm的激光可实现更高的光热效率。由于光热效率更高，偏振方向垂直于铜纳米线长轴的激光照射下铜纳米线的熔化阈值为32 mW，比偏振方向平行于铜纳米线长轴的激光照射下的铜纳米线低约20%。
