Wang Zhi, Yi Peng, Wang Andong, Li Taoyong, Chen Wentao, Qi Xiaolin, Li Xiaowei
School of Mechanical Engineering, Beijing Institute of Technology, No. 5 Zhonggguancun South Street, Haidian Beijing, Beijing 100081, China.
Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China.
Nanophotonics. 2025 Mar 27;14(9):1345-1353. doi: 10.1515/nanoph-2024-0690. eCollection 2025 Apr.
The focused vortex beam generates a hollow beam, which has been widely used for size-controlled nanoparticle formation on various materials. However, the size variation of the vortex beam is limited by the integral order of the 2π phase wrap, while the waste is caused by the large side lobe around the center. In this study, we propose a method for hollow beam generation by splitting a femtosecond laser and imparting opposite phases to the outer annular region and the central Gaussian region. After focusing, these two regions overlap at the focal spot, resulting in a hollow beam due to phase cancellation. By modulating the relative dimensions of these two regions, the hollow center can be continuously varied. When such a hollow beam is used for surface processing, the thermal capillary effect facilitates the convergence of the molten material toward the center, ultimately leading to the formation of nanoparticles. This ability to control size allows precise control of nanoparticle size with a diameter range from 140 nm to 940 nm. This method holds great promise for guiding research into nanoparticle properties that are influenced by size effects.
聚焦涡旋光束会产生空心光束，这种光束已被广泛用于在各种材料上形成尺寸可控的纳米颗粒。然而，涡旋光束的尺寸变化受到2π相位缠绕整数阶数的限制，同时中心周围的大旁瓣会造成能量浪费。在本研究中，我们提出了一种通过将飞秒激光分开并给外环形区域和中心高斯区域赋予相反相位来产生空心光束的方法。聚焦后，这两个区域在焦点处重叠，由于相位抵消而产生空心光束。通过调节这两个区域的相对尺寸，可以连续改变空心中心的大小。当这种空心光束用于表面处理时，热毛细效应有助于熔融材料向中心汇聚，最终导致纳米颗粒的形成。这种控制尺寸的能力使得能够精确控制直径范围从140纳米到940纳米的纳米颗粒尺寸。该方法对于指导受尺寸效应影响的纳米颗粒性质的研究具有很大的前景。
