Chen Yan, Pu Shiliang, Hou Mingming, Li Linhan, Liu Sitan, Li DaPeng, Yi Fei
Opt Express. 2025 Mar 10;33(5):11555-11573. doi: 10.1364/OE.555456.
Flat-top laser beams have significant applications in fields such as laser processing due to their uniform intensity distribution and clear boundaries. Since lasers typically emit Gaussian beams in the fundamental mode, devices that convert Gaussian beams into flat-top beams are essential. However, traditional beam shapers composed of refractive or diffractive optical elements need improvements in volume, weight, and cost. In this study, we propose a beam-shaping metalens to address these issues. We present an extended Gerchberg-Saxton (GS) algorithm to design two beam-shaping metalenses that convert Gaussian beams into 2D circular and square flat-top beams, respectively. We develop an analytical rapid simulation (ARS) method for simulating metalenses and verify its accuracy. Additionally, we consider the microloading effect in etching and compensate for the impact caused by etching depth inconsistencies. We experimentally fabricated and characterized two beam-shaping metalenses, achieving a circular flat-top beam with a conversion efficiency of 91.8% and an RMS value of 16.7%, and a square flat-top beam with a conversion efficiency of 89.7% and an RMS value of 24.0%. This method for designing beam-shaping metalenses that convert Gaussian beams into flat-top beams of arbitrary shapes provides a novel solution for laser beam shaping.
平顶激光束由于其均匀的强度分布和清晰的边界，在激光加工等领域有着重要应用。由于激光器通常在基模下发射高斯光束，因此将高斯光束转换为平顶光束的器件至关重要。然而，由折射或衍射光学元件组成的传统光束整形器在体积、重量和成本方面需要改进。在本研究中，我们提出了一种光束整形超表面透镜来解决这些问题。我们提出了一种扩展的格尔奇伯格 - 萨克斯顿（GS）算法，以设计两种分别将高斯光束转换为二维圆形和平方形平顶光束的光束整形超表面透镜。我们开发了一种用于模拟超表面透镜的解析快速模拟（ARS）方法并验证了其准确性。此外，我们考虑了蚀刻中的微负载效应，并补偿了蚀刻深度不一致所造成的影响。我们通过实验制作并表征了两种光束整形超表面透镜，实现了转换效率为91.8%、均方根值为16.7%的圆形平顶光束，以及转换效率为89.7%、均方根值为24.0%的方形平顶光束。这种将高斯光束转换为任意形状平顶光束的光束整形超表面透镜设计方法为激光光束整形提供了一种新颖的解决方案。
