暨南大学团队提出超构光栅结构,高效率实现对光场相位的连续阶调控
作者:Zi-Lan Deng, Junhong Deng, Xin Zhuang, Shuai Wang, Tan Shi, Guo Ping Wang, Yao Wang, Jian Xu, Yaoyu Cao, Xiaolei Wang, Xing Cheng, Guixin Li, Xiangping Li
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2018-11-11 22:57:27
能实现对光场任意调控的超表面,是近年来纳米光子学领域的研究热点。现有的超表面调控光场相位的方式一般包括形状编码型、大小编码型及转角编码型,这往往仅在较窄的入射角范围内才能对光场相位的离散多阶进行精确调控。暨南大学李向平教授等受传统全息光学里的迂回相位启发,提出了一种超常光学衍射(EOD)的超构光栅结构,此EOD超构光栅通过调控金属纳米棒在每个周期内的位移量实现0~2π连续阶相位的调控,其调制的相位与位移量呈线性关系,而不依赖于入射光波长与入射角。不同于传统迂回相位中通光孔径衍射效率低、出现孪生像等缺点,此超构光栅采用精心设计的金属纳米棒替代传统的通光孔结构,金属纳米棒的局域表面等离激元共振效应可以将光衍射效率增强到90%以上,并完全抑制0级光的出现。另一方面,由于加工超表面结构的纳米制备技术(如EBL, FIB等)在控制纳米结构位置的精准度,比控制纳米结构形状与大小要高得多,此位移编码型超表面能大大降低超表面的制备难度与成本,为宽角度范围波前调控,全景全息等应用提供了优良平台。
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Facile Metagrating Holograms with Broadband and Extreme Angle Tolerance
作者:Zi-Lan Deng, Junhong Deng, Xin Zhuang, Shuai Wang, Tan Shi, Guo Ping Wang, Yao Wang, Jian Xu, Yaoyu Cao, Xiaolei Wang, Xing Cheng, Guixin Li, Xiangping Li
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2018-11-11 22:57:27
导语
The emerging meta-holograms rely on arrays of intractable meta-atoms with various geometries and sizes for customized phase profiles that can precisely modulate the phase of a wavefront at an optimal incident angle for given wavelengths. The stringent and band-limited angle tolerance remains a fundamental obstacle for their practical application, in addition to high fabrication precision demands. Utilizing a different design principle, we determined that facile metagrating holograms based on extraordinary optical diffraction can allow the molding of arbitrary wavefronts with extreme angle tolerances (near-grazing incidence) in the visible–near-infrared regime. By modulating the displacements between uniformly sized meta-atoms rather than the geometrical parameters, the metagratings produce a robust detour phase profile that is irrespective of the wavelength or incident angle. The demonstration of high-fidelity meta-holograms and in-site polarization multiplexing significantly simplifies the metasurface design and lowers the fabrication demand, thereby opening new routes for flat optics with high performances and improved practicality.
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