技术领域technical field
本发明属于超表面领域，特别是涉及一种自旋选择超表面及手性超透镜。The invention belongs to the field of metasurfaces, in particular to a spin selection metasurface and a chiral metalens.
背景技术Background technique
超表面是一种新型人造纳米器件，其对于电磁波振幅、相位、偏振等多个自由度有着灵活的调控能力。超表面的相位调制基于光在界面处的突然的相位改变，因此有着超薄超小的独特优势，为突破衍射极限，集成光路创造了可能。Metasurface is a new type of man-made nano-device, which has flexible control ability for electromagnetic wave amplitude, phase, polarization and other degrees of freedom. The phase modulation of the metasurface is based on the sudden phase change of light at the interface, so it has the unique advantage of being ultra-thin and ultra-small, which creates the possibility of breaking through the diffraction limit and integrating optical circuits.
在现代生物研究中，根据圆二色性分辨手性十分重要，手性检测系统为了获取所需的不同类型的偏振态，通常需要级联多个偏振光学元件，增加了系统的体积，阻碍了现代光学器件向集成化和小型化的发展。手性超表面对左右旋圆偏振光不对称传输，可以实现对其中一个圆偏振光自旋选择的同时进行波前调制功能，在手性检测系统中有着极大的应用前景。In modern biological research, it is very important to distinguish chirality based on circular dichroism. In order to obtain the required different types of polarization states, a chiral detection system usually needs to cascade multiple polarization optical elements, which increases the volume of the system and hinders Modern optical devices are developing toward integration and miniaturization. The chiral metasurface asymmetrically transmits left and right circularly polarized light, and can realize the function of wavefront modulation while selecting the spin of one of the circularly polarized light, which has great application prospects in chiral detection systems.
以往手性超表面设计方法往往通过改变单元结构尺寸实现对电磁波的控制，由于超表面既需要满足自旋选择特性，同时要提供全相位的调制数据库，因此需要仿真大量的单元结构，需要大量的计算资源。对这样一个超表面器件的设计，需要对其需要的相位分布进行8阶、16阶等多阶量化，通过查表的方式从大量仿真数据库中选取最接近的相位和其对应的结构参数，会导致较大的误差。In the past, the chiral metasurface design method often achieved the control of electromagnetic waves by changing the size of the unit structure. Since the metasurface needs to meet the spin selection characteristics and provide a full-phase modulation database, it is necessary to simulate a large number of unit structures and require a large number of computing resources. For the design of such a metasurface device, it is necessary to carry out multi-level quantization such as 8th order and 16th order for the required phase distribution, and select the closest phase and its corresponding structural parameters from a large number of simulation databases by means of table lookup. lead to large errors.
发明内容Contents of the invention
针对现有技术问题与改进需求，本发明提供一种自旋选择超表面的设计，旨在解决目前自旋选择手性超表面的设计方法需要大量仿真计算工作以及查表获取结构参数存在误差的问题，可以应用在手性检测、偏振成像等领域中。In view of the existing technical problems and improvement needs, the present invention provides a spin-selective metasurface design, which aims to solve the problem that the current spin-selective chiral metasurface design method requires a lot of simulation and calculation work and there are errors in the structural parameters obtained by looking up the table. It can be applied in chiral detection, polarization imaging and other fields.
本发明的技术解决方案如下：Technical solution of the present invention is as follows:
一方面，本发明提供一种自旋选择自旋选择超表面，其特点在于，包括基底和分布在该基底上的四角呈对角分布的四个各向异性的微结构，且呈对角的两两微结构的尺寸与旋转角度互相相同，并与相邻两个微结构的尺寸与旋转角度互不相同。In one aspect, the present invention provides a spin-selective spin-selective metasurface, which is characterized in that it includes a substrate and four anisotropic microstructures distributed on the substrate in a diagonal distribution, and the diagonal The sizes and rotation angles of any pair of microstructures are the same as each other, and are different from the size and rotation angles of two adjacent microstructures.
单元结构1与单元结构3尺寸与旋转角度相同，均为第一种纳米柱；单元结构2与单元结构4尺寸与旋转角度相同，均为第二种纳米柱。Unit structure 1 and unit structure 3 have the same size and rotation angle, and both are the first type of nanopillar; unit structure 2 and unit structure 4 have the same size and rotation angle, and both are the second type of nanopillar.
进一步地，四个单元结构1、2、3、4的旋转角分别为：β、α+β、β、α+β；通过控制四个单元结构旋转角可以在实现对左右旋圆偏振光自旋选择的同时进行相位调制。Further, the rotation angles of the four unit structures 1, 2, 3, and 4 are: β, α+β, β, α+β; by controlling the rotation angles of the four unit structures, the left and right circularly polarized light can be automatically rotated. Phase modulation is performed while rotating the selection.
进一步地，四个单元结构旋转角可以看作单元结构2、4的相对旋转角α和四个单元结构1、2、3、4整体旋转角β的叠加。其中相对旋转角α控制自旋选择，整体旋转角β实现全相位调制。Further, the rotation angles of the four unit structures can be regarded as the superposition of the relative rotation angle α of the unit structures 2, 4 and the overall rotation angle β of the four unit structures 1, 2, 3, 4. Among them, the relative rotation angle α controls the spin selection, and the overall rotation angle β realizes all-phase modulation.
进一步地，对于超表面基本单元结构参数的设计方案为：固定相邻单元结构间的相对旋转角α＝π/4，设置超表面基本单元周期与第一种矩形纳米柱和第二种矩形纳米柱的尺寸参数为变量，参数扫描寻找实现对于入射右旋光正交转化透过率最大，同时左旋光正交转化透过率时，获取超表面基本单元结构参数。Further, the design scheme for the structural parameters of the basic unit of the metasurface is: fix the relative rotation angle α=π/4 between adjacent unit structures, set the basic unit period of the metasurface and the first type of rectangular nano-pillar and the second type of rectangular nano-pillar The size parameter of the column is a variable, and the parameters are scanned to find the maximum transmittance for the orthogonal conversion of the incident right-handed light, and at the same time, when the transmittance of the left-handed light is orthogonally converted, the structural parameters of the basic unit of the metasurface are obtained.
进一步地，相对旋转角α对自旋选择的设计方案为：当相对旋转角α＝π/4，超表面基本单元可以实现对右旋光的自旋选择，即对入射的右旋光高透，而阻断左旋光。当相对旋转角α＝-π/4，超表面基本单元可以实现对左旋光的自旋选择。Furthermore, the design scheme for the spin selection of the relative rotation angle α is: when the relative rotation angle α=π/4, the metasurface basic unit can realize the spin selection for the right-handed light, that is, the incident right-handed light is highly transparent , while blocking the left-handed light. When the relative rotation angle α=-π/4, the basic unit of the metasurface can realize the spin selection of left-handed light.
进一步地，整体旋转角β对相位的设计方案为：根据超表面器件的波前调制需要求，可以获取每个像素点位置上需要的相位分布Φ(x，y)。当则每个像素点位置处单元结构的整体旋转角为：Further, the design scheme of the overall rotation angle β versus phase is: according to the wavefront modulation requirements of the metasurface device, the required phase distribution Φ(x, y) at each pixel position can be obtained. Then the overall rotation angle of the unit structure at each pixel position is:
进一步地，四个单元结构1、2、3、4的旋转角分别为：由于超表面调制原理限制，无法直接确定符号的正负，可以简单仿真一些不同β角的超表面单元确定正负符号的选取。Further, the rotation angles of the four unit structures 1, 2, 3, and 4 are: Due to the limitations of the metasurface modulation principle, it is impossible to directly determine the sign of the sign, and some metasurface units with different β angles can be simply simulated to determine the selection of the sign.
进一步地，将每个像素点位置上的按上述尺寸参数与旋转角度排列，即可以获取一种自旋选择的超表面。Furthermore, a spin-selected metasurface can be obtained by arranging the above-mentioned size parameters and rotation angles at each pixel position.
另一方面，本发明还提供一种自旋选择超表面透镜，其特点在于，包括上述自旋选择超表面。On the other hand, the present invention also provides a spin-selective metasurface lens, which is characterized in that it includes the above-mentioned spin-selective metasurface.
与现有技术相比，本发明的有益效果是：Compared with prior art, the beneficial effect of the present invention is:
1)通过对四个微结构旋转角的控制，就可以实现对左右旋圆偏振光的自旋选择，节省了大量计算资源。1) By controlling the rotation angles of the four microstructures, the spin selection of left and right circularly polarized light can be realized, which saves a lot of computing resources.
2)可以根据需要的相位分布直接计算出每个单元结构的旋转角度，避开了量化相位后通过查表方式选取每个单元结构的参量，减少了目标相位与仿真相位之间的误差。2) The rotation angle of each unit structure can be directly calculated according to the required phase distribution, and the parameters of each unit structure can be selected by looking up the table after avoiding the quantization phase, reducing the error between the target phase and the simulated phase.
附图说明Description of drawings
图1为本发明自旋选择超表面结构的俯视图；Fig. 1 is the top view of the spin selection metasurface structure of the present invention;
图2为本发明自旋选择超表面结构参数示意图。Fig. 2 is a schematic diagram of the structural parameters of the spin-selective metasurface of the present invention.
图3为本发明实施例中超表面基本单元对左右旋圆偏振光正交偏振转化的透过率曲线。Fig. 3 is the transmittance curve of the metasurface basic unit to the orthogonal polarization conversion of left and right circularly polarized light in the embodiment of the present invention.
图4为本发明实施例中超表面基本单元旋转整体旋转角β对振幅和相位的调制关系。Fig. 4 shows the modulation relationship between the overall rotation angle β of the basic unit of the metasurface and the amplitude and phase in the embodiment of the present invention.
图5为本发明实施例中超透镜在左右旋圆偏振光入射下的聚焦成像效果。Fig. 5 shows the focusing imaging effect of the metalens under the incident left and right circularly polarized light in the embodiment of the present invention.
具体实施方式Detailed ways
为使本发明实施例的目的、技术方案和优点更加清楚，下面将结合附图对本发明的各实施方式进行详细的阐述。然而，本领域的普通技术人员可以理解，在本发明各实施方式中，为了使读者更好地理解本申请而提出了许多技术细节。但是，即使没有这些技术细节和基于以下各实施方式的种种变化和修改，也可以实现本申请所要求保护的技术方案。以下各个实施例的划分是为了描述方便，不应对本发明的具体实现方式构成任何限定，各个实施例在不矛盾的前提下可以相互结合相互引用。In order to make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, various implementation modes of the present invention will be described in detail below in conjunction with the accompanying drawings. However, those of ordinary skill in the art can understand that, in each implementation manner of the present invention, many technical details are provided for readers to better understand the present application. However, even without these technical details and various changes and modifications based on the following implementation modes, the technical solutions claimed in this application can also be realized. The division of the following embodiments is for the convenience of description, and should not constitute any limitation to the specific implementation of the present invention, and the various embodiments can be combined and referenced to each other on the premise of no contradiction.
一种自旋选择手性超透镜，包括：四个各向异性的矩形纳米柱作为超表面器件的基本组成单位，通过改变四个纳米柱的旋转角可以实现对圆偏振光的自旋选择全相位调制，从而构建出需要的超透镜相位分布。A spin-selective chiral metalens, including: four anisotropic rectangular nanopillars as the basic unit of the metasurface device, by changing the rotation angle of the four nanopillars, the spin selection of circularly polarized light can be fully realized Phase modulation to construct the desired phase distribution of the metalens.
所述超表面设计方法包括步骤：Described metasurface design method comprises steps:
S1：如图1所示，本发明设计的超透镜基本单元由四个各向异性的矩形纳米柱组成。其中，单元结构1与单元结构3尺寸与旋转角度相同，均为第一种纳米柱；单元结构2与单元结构4尺寸与旋转角度相同，均为第二种纳米柱。超表面基本单元的结构参数包含：超表面基本单元结构周期P与、第一种纳米柱和第二种纳米柱的长宽高L1、L2、W1、W2、H，标注在图二中。S1: As shown in Figure 1, the basic unit of the metalens designed in the present invention consists of four anisotropic rectangular nanopillars. Among them, unit structure 1 and unit structure 3 have the same size and rotation angle, and both are the first type of nanopillar; unit structure 2 and unit structure 4 have the same size and rotation angle, and both are the second type of nanopillar. The structural parameters of the basic unit of the metasurface include: the structural period P of the basic unit of the metasurface, the length, width and height L1 , L2 , W1 , W2 , and H of the first type of nanopillar and the second type of nanopillar, marked in Fig. Second middle school.
S2：超表面基本单元的结构参数通过以下步骤获取：使用TiO2作为矩形纳米柱1、2、3、4的介质材料，SiO2作为超表面基底5。固定纳米柱间的相对旋转角α＝π/4，中心波长设置为532nm，仿真扫描超表面基本单元的结构参数，最终结果实现对两个自旋圆偏振光最大的不对称传输如图2所示。获取此时仿真的结构参数，列举在图3中。S2: The structural parameters of the basic unit of the metasurface were obtained by usingTiO2 as the dielectric material of the rectangular nanopillars 1, 2, 3, 4 andSiO2 as the metasurface substrate 5. Fix the relative rotation angle α=π/4 between the nanopillars, set the central wavelength to 532nm, simulate and scan the structural parameters of the basic unit of the metasurface, and finally achieve the maximum asymmetric transmission of the two spin circularly polarized light, as shown in Figure 2 Show. Obtain the structural parameters of the simulation at this time, listed in Figure 3.
S3：对于右旋选择超表面，固定纳米柱间的相对旋转角α＝π/4，叠加每个纳米柱的整体旋转角β，当β从0旋转到180°时，对应的调制相位如图4，即实现-2β的相位调制。S3: For a right-handed selective metasurface, the relative rotation angle between the nanopillars is fixed α=π/4, and the overall rotation angle β of each nanopillar is superimposed. When β rotates from 0 to 180°, the corresponding modulation phase is shown in the figure 4. That is to realize the phase modulation of -2β.
S3：根据透镜相位分布公式：获取每个像素点位置上需要的相位响应。S3: According to the lens phase distribution formula: Obtain the desired phase response at each pixel location.
S4：根据S3中获取的相位分布，对于一种右旋选择手性超透镜，可以计算出每个像素点位置上单元结构的-Φ(x,y)/2、π/4-Φ(x,y)/2、-Φ(x,y)/2、π/4-Φ(x,y)/2。S4: According to the phase distribution obtained in S3, for a right-handed selective chiral metalens, -Φ(x,y)/2, π/4-Φ(x ,y)/2, -Φ(x,y)/2, π/4-Φ(x,y)/2.
S5：结合步骤S2与步骤S4中超表面基本单元结构参量与单元结构旋转角，对每个像素点位置上进行超表面单元结构的排列，最终获得一种自旋选择手性超透镜。S5: Combining the parameters of the basic unit structure of the metasurface and the rotation angle of the unit structure in step S2 and step S4, arrange the unit structure of the metasurface at each pixel position, and finally obtain a spin-selective chiral metalens.
S6：使用电子束光刻根据S5设计的超透镜单元结构排列加工出一种右旋选择超透镜，其在两种自旋圆偏振光照射下的聚焦成像效果如图5所示，在右旋光入射下超透镜聚焦成像，在左旋光下的抑制了噪声。S6: Using electron beam lithography to process a right-handed selective metalens according to the arrangement of the metalens unit structure designed in S5, its focusing and imaging effects under the irradiation of two kinds of spin circularly polarized light are shown in Figure 5. Under light incidence, the superlens is focused and imaged, and the noise is suppressed under left-handed light.
本发明提供了一种自旋选择超表面的设计方法，使用四个各向异性的单元结构作为超表面器件的基本组成单位，只需仿真出两种各向异性单元结构，根据超表面器件需要的相位分布，通过简单计算就可以求出每个单元结构需要的旋转角度，十分灵活且具有高精度。The invention provides a design method for a spin-selective metasurface. Four anisotropic unit structures are used as the basic unit of the metasurface device. Only two anisotropic unit structures need to be simulated. According to the requirements of the metasurface device The phase distribution of the phase distribution, the rotation angle required by each unit structure can be obtained by simple calculation, which is very flexible and has high precision.
尽管上面已经示出和描述了本发明的实施例，可以理解的是，上述实施例是示例性的，不能理解为对本发明的限制。本领域的普通技术人员在本发明的范围内可以对上述实施例进行变化、修改、替换和变型。Although the embodiments of the present invention have been shown and described above, it should be understood that the above embodiments are exemplary and should not be construed as limitations on the present invention. Those skilled in the art can make changes, modifications, substitutions and modifications to the above-mentioned embodiments within the scope of the present invention.
以上本发明的具体实施方式，并不构成对本发明保护范围的限定。任何根据本发明的技术构思所做出的各种其他相应的改变与变形，均应包含在本发明权利要求的保护范围内。The above specific implementation manners of the present invention do not constitute a limitation to the protection scope of the present invention. Any other corresponding changes and modifications made according to the technical concept of the present invention shall be included in the protection scope of the claims of the present invention.
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| CN118938360B (en)* | 2024-08-01 | 2025-05-13 | 内蒙古工业大学 | Spatially multiplexed wideband and narrowband wavefront-controlled super-structured surface device and design method thereof |
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