Chen Lei, Kanwal Saima, Lu Yongzheng, Zhang Dawei, Chen Xu, Chen Jian, Wen Jing
Engineering Research Center of Optical Instrument and Systems, Ministry of Education and Shanghai Key Lab of Modern Optical System, University of Shanghai for Science and Technology, No. 516 Jun Gong Road, Shanghai, 200093, China.
School of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, Shanghai, 200093, China.
Nanophotonics. 2022 Feb 15;11(6):1203-1210. doi: 10.1515/nanoph-2021-0787. eCollection 2022 Feb.
Self-accelerating polygon beams have drawn growing emphasis in optics owing to their exceptional characteristics of multiple self-accelerating channels and needle-like field distributions. Various approaches have been proposed to generate polygon beams, such as using spatial light modulators (SLMs) or plasmonic metasurfaces. However, SLMs impede the miniaturization of the optical system and both approaches are subject to low efficiencies and demand an extra physical lens with a long focal length for Fourier transform, which limits the quality and the diverse variability of polygon beams. In this article, we demonstrate the generation of high-quality accelerating polygon beams in broadband spectra of 500-850 nm by utilizing dielectric metasurfaces. These metasurfaces integrate the functionality of the Fourier transform lens to enable the resulting beams with a large curvature ratio for the self-accelerating channels and a relatively small size for the autofocus region. The curvature ratio of the beam at = 633 nm is 31 times higher than the previously reported plasmonic-based method. While the size of the focused spot is 2.35 µm, which is reduced by nearly 15 times. The proposed beam generator provides ample opportunities for applications such as particle micromanipulation, beam shaping, laser fabrication, and biomedical imaging.
自加速多边形光束因其具有多个自加速通道和针状场分布的特殊特性，在光学领域受到越来越多的关注。人们已经提出了各种方法来产生多边形光束，例如使用空间光调制器（SLM）或等离子体超表面。然而，空间光调制器阻碍了光学系统的小型化，并且这两种方法都存在效率低的问题，并且需要一个额外的长焦距物理透镜进行傅里叶变换，这限制了多边形光束的质量和多样的可变性。在本文中，我们展示了利用介电超表面在500 - 850纳米的宽带光谱中产生高质量的加速多边形光束。这些超表面集成了傅里叶变换透镜的功能，使得产生的光束具有用于自加速通道的大曲率比和用于自聚焦区域的相对小尺寸。在波长λ = 633纳米时，光束的曲率比比先前报道的基于等离子体的方法高31倍。而聚焦光斑的尺寸为2.35微米，减小了近15倍。所提出的光束发生器为粒子微操纵、光束整形、激光制造和生物医学成像等应用提供了充足的机会。
