PROCEEDINGS OF SPIESPIEDigitalLibrary.org/conference-proceedings-of-spieDesign of broadband achromaticmetalens in the visibleYuanyuan Xu,Yu Liang,Yang Zou,Shuangshuang Xue,Jingrong Liao,et al.Yuanyuan Xu,Yu Liang,Yang Zou,Shuangshuang Xue,Jingrong Liao,Wenyan Pan,Yawei Wang,"Design of broadband achromatic metalens in thevisible,"Proc.SPIE 11608,Optics Frontiers Online 2020:Micro andNanophotonics (OFO-4 2020),116080B(24 December 2020);doi:10.1117/12.2587310SPIE.Event:Optics Frontiers Online 2020:Micro and Nanophotonics (OFO-4 2020).2020,Online OnlyDesign of broadband achromatic metalens in the visibleXu Yuanyuan",Liang Yu,Zou Yang,Xue Shuangshuang",Liao Jingrong,Pan Wenyan",Wang Yaweia School of Physics and Electronic Engineering,Jiangsu University,Zhenjiang,Jiangsu212013,China;bJingjiang College,Jiangsu University,Zhenjiang,Jiangsu 212013,China;School of Mechanical Engineering,Jiangsu University,Zhenjiang,Jiangsu212013,China;AbstractAs an important parameter for evaluating optical devices,chromatic aberration is an enduring research hotspot in optics.The traditional bulk lens relies on the polished surface profile on the transparent optical material to achieve the requiredgradual phase change.Compared with the traditional lens,the metalens can achieve the effect of focusing the beam witha more suitable small size standard.In this paper,the geometric phase method is used to realize the phase shift requiredby the surface of the achromatic metalens through the unique design of the nano-unit column array.In order to beapplied to the optical path of multi-wavelength phase microscopy imaging,the metalens designed in this papereffectively eliminates chromatic aberration in the visible light band from 500 nm to 595 nm and improves the imagingresolution.It also satisfy the needs of modem optical devices for ultra-light,ultra-thin and easy portability,and can beused in a variety of optical instruments,aerospace and military fields.Keywords:Metalens,visible light,geometric phase,achromatic1.INTRODUCTIONWith the continuous excavation of a variety of novel materials,the defects of traditional optical devices to control thewavefront of light are gradually being improved.Metalens,as a new type of ultra-thin and portable optical devicel-does not rely on accumulation along the optical path.The phase difference realizes the control of the beam,but directlythrough the change of the geometric parameters of the unit column in the metalens and the reasonable arrangement ofthe array,the arbitrary control of the amplitude,phase and polarization of the electromagnetic wave is realized.In 1968,Versalago took the lead in researching negative refractive index mediali.In 2000,Pendry of Harvard University putforward the concept of perfect lens.In 2008,Luo Xiangang's group at the State Key Laboratory of Microfabricationused metasurface devices to achieve beam refraction and reflectionl2).In 2015,Zhao Zeyu of the State Key Laboratoryof Microfabrication and others designed an achromatic metalens for three wavelengths(532 nm,632.8 nm,785 nm)insilicon strips to prepare achromatic deflection devices at three wavelengths (1300 nm,1550 nm,and 1800 nm)in thecomplementary functional units to realize a wide-band achromatic metalens with visible light from 400 nm to 660 nmlIn this study,a reflective achromatic metalens has been realized using the principle of phase compensation.In order toOptics Frontiers Online 2020:Micro and Nanophotonics(OFO-42020),edited by Hui Liu,Proc.of SPIEVol.11608.116080B·©2020SPIE·CCC code:0277-786XW20/s21·doi10.1117/12.2587310Proc.of SPIE Vol.11608 116080B-1Terms of Use:https:/www.spiedigitallibrary.org/terms-of-usebe more convenient to be used in a variety of optical systems,the geometric phase method is used to design a metalensthat effectively eliminates chromatic aberration in the visible light band from 500 nm to 595 nm.The lens is constructedand compared with the metalens designed based on the phase compensation principle,the design process is moreconvenient.2.FUNDAMENTALSIn this paper,CST Studio Suite three-dimensional electromagnetic simulation software is used to optimize the shape,rotation angle and material of the cuboid nano unit column,and the achromatic effect of the metalens is achieved bydesigning the geometric parameters and arrangement of the functional unit.Use the CST simulation software to scan theparameters of the basic functional unit to obtain the phase values corresponding to the different parameter unit columns,as shown in Figure 1.0.80.60.2530nm580nm0.080160240320400Width (nm)Figure 1.Phase values corresponding to different parameters of the basic unit of the metalens.Since the unit column has no modulation effect on the phase of the same polarization state,the efficiency of the crosspolarization state should be improved as much as possible.According to the geometric phase characteristics,when theleft-handed circularly polarized light(LCP)is incident,the metalens can control the electromagnetic wave,Make theright-handed circularly polarized light (RCP)produce focusing effect.On the contrary,if the right-handed circularlypolarized light (RCP)is incident,the light will be left-handed circularly polarized light (LCP)and the lens will have adivergent effect.The two different phase response values of the polarization state to the same direction angle areopposite to each other.When the incident light is a single circularly polarized light,among the two differently rotatedcircularly polarized lights in the outgoing light,the circularly polarized light opposite to the incident light contains anadditional phase factor,which is the geometric phase 20.The metalens is based on the geometric phase method toregulate the electromagnetic wave,which can be expressed by the electromagnetic wave transmission matrix formula 1:TT(1)In the formula:when linearly polarized light is polarized incident from the x direction,the polarization transmissionProc.of SPIE Vol.11608 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