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| 用宽带超表面产生阵列贝塞尔光束 |
| Generation of Bessel beam array using broadband metasurfaces |
| 投稿时间：2020-01-10 |
| DOI：10.3969/j.issn.1005-5630.2020.05.004 |
| 中文关键词: 阵列贝塞尔光束 电介质超表面 宽波段 |
| 英文关键词:Bessel beam array dielectric metasurface broadband |
| 基金项目:国家自然科学基金（81701745）；国家重点研发计划（2018YFA0701800）；上海市科委创新行动计划（18DZ1100400） |
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| 中文摘要: |
| 通过在空间光调制器（SLM）上加载相位图或通过光刻加工微型圆锥状结构可以产生贝塞尔光束阵列。然而，典型空间光调制器具有比波长大一个数量级的像素尺寸，这限制了相位梯度的可用范围，用光刻法加工的微型锥透镜的顶端不是标准的圆锥，这影响了贝塞尔光束的质量。为了克服这些缺点，将复杂的相位图加载到电介质超表面上，设计了一种可以产生阵列贝塞尔光束（在波长700 nm处，NA=0.3）的超表面器件。该器件可以宽波段工作，其单元结构在波长580~800 nm范围内的偏振转换效率均超过57%。利用时域有限差分算法（FDTD）对该器件（厚度为380 nm，直径仅为40 μm）进行了仿真，所产生的阵列光束都垂直于超表面器件。所提出的阵列贝塞尔光束发生器具有纳米级别的厚度和几十微米的直径，这对于未来的集成光学领域具有很大的应用前景。 |
| 英文摘要: |
| Bessel beam arrays can be generated by loading a phase map on a spatial light modulator (SLM) or a microaxicon-like structures fabricated by lithography. However, the pixel size of a typical SLM is more than one order of magnitude larger than the wavelength of visible light, which limits the available range of phase gradient. And the tip of the micro-axicon-like structures fabricated by lithography is not a standard cone, which affects the quality of the Bessel beam. In order to overcome these shortcomings, a device that can generate Bessel beam array (at a wavelength of 700 nm, NA = 0.3) is designed by loading a complex phase map onto the dielectric metasurface. The device can work in a broadband, the polarization conversion efficiencies of one nanopost remains higher than 57% at the wavelength range from λ=590 nm to λ=800 nm. This device (thickness of 380 nm and diameter of only 40 μm) was simulated by the three-dimensional finite difference time domain (FDTD). The array beams generated were perpendicular to the metasurface device. The proposed Bessel beam array generator has a thickness of nanometer level and a diameter of several tens of micrometers, which has great application prospects in the field of integrated optics in the future. |
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