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Yang Y, Zhang X, Liu K, Zhang H, Shi L, He M, Guo Y. Exploring the limits of metasurface polarization multiplexing capability based on deep learning. OPTICS EXPRESS 2023; 31:17065-17075. [PMID: 37157770 DOI: 10.1364/oe.490002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Metasurfaces provide a new approach for planar optics and thus have realized multifunctional meta-devices with different multiplexing strategies, among which polarization multiplexing has received much attention due to its convenience. At present, a variety of design methods of polarization multiplexed metasurfaces have been developed based on different meta-atoms. However, as the number of polarization states increases, the response space of meta-atoms becomes more and more complex, and it is difficult for these methods to explore the limit of polarization multiplexing. Deep learning is one of the important routes to solve this problem because it can realize the effective exploration of huge data space. In this work, a design scheme for polarization multiplexed metasurfaces based on deep learning is proposed. The scheme uses a conditional variational autoencoder as an inverse network to generate structural designs and combines a forward network that can predict meta-atoms' responses to improve the accuracy of designs. The cross-shaped structure is used to establish a complicated response space containing different polarization state combinations of incident and outgoing light. The multiplexing effects of the combinations with different numbers of polarization states are tested by utilizing the proposed scheme to design nanoprinting and holographic images. The polarization multiplexing capability limit of four channels (a nanoprinting image and three holographic images) is determined. The proposed scheme lays the foundation for exploring the limits of metasurface polarization multiplexing capability.
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Khalid AUR, Ullah N, Han Y, Yuan X, Feng F, Somekh MG. Metasurface Based Spin‐Selective Wollaston‐and‐Rochon‐Prism‐Like Circularly Polarized Beam Splitter. ADVANCED THEORY AND SIMULATIONS 2022. [DOI: 10.1002/adts.202200574] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Affiliation(s)
- Ata Ur Rahman Khalid
- Nanophotonics Research Center Shenzhen Key Laboratory of Micro‐Scale Optical Information Technology and Institute of Microscale Optoelectronics Shenzhen University Shenzhen 518060 P. R. China
| | - Naeem Ullah
- College of Physics and optoelectronics engineering Shenzhen University Shenzhen Guangdong 518060 P. R. China
| | - Yu Han
- Beijing Engineering Research Center for Mixed Reality and Advanced Display School of Optics and Photonics Beijing Institute of Technology Beijing 100081 P. R. China
| | - Xiaocong Yuan
- Nanophotonics Research Center Shenzhen Key Laboratory of Micro‐Scale Optical Information Technology and Institute of Microscale Optoelectronics Shenzhen University Shenzhen 518060 P. R. China
| | - Fu Feng
- Nanophotonics Research Center Shenzhen Key Laboratory of Micro‐Scale Optical Information Technology and Institute of Microscale Optoelectronics Shenzhen University Shenzhen 518060 P. R. China
| | - Michael Geoffrey Somekh
- Nanophotonics Research Center Shenzhen Key Laboratory of Micro‐Scale Optical Information Technology and Institute of Microscale Optoelectronics Shenzhen University Shenzhen 518060 P. R. China
- Faculty of Engineering University of Nottingham Nottingham NG7 2RD UK
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Li Z, Zhang Y, Huang H, Qin S, Jie K, Liu H, Guo J, Meng H, Wang F, Yang X, Wei Z. Dual-channel metasurfaces for independent and simultaneous display in near-field and far-field. OPTICS EXPRESS 2022; 30:18434-18446. [PMID: 36221644 DOI: 10.1364/oe.461402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Accepted: 04/21/2022] [Indexed: 06/16/2023]
Abstract
The operation of near-field and far-field can be employed to display holographic and nanoprinting images, which significantly improves the information density. Previous studies have proposed some approaches to display the images independently or simultaneously, but cannot satisfy these two characteristics in a single structure under the same incident light. Here, a single layer multifunctional metasurface is proposed to display a nanoprinting image and a holographic image independently and simultaneously. By tailoring the dimensions of each nanobricks and adopting different orientation angle, the amplitude and phase can be artificially designed. Moreover, enabled by the simulated annealing algorithm, we take the impact of both amplitude and phase of each nanobrick into consideration, which eliminates the unnecessary influence of amplitude on holographic image. Compared with previous work, our metasurfaces markedly improve the quality of holographic image with simple structures while not affecting the nanoprinting image. To be exact, it breaks the coupling between the near-field and far-field, achieving independent and simultaneous control of both fields. Our proposed metasurfaces carry characteristics of simple manufacture, little crosstalk, and great compactness, which provides novel applications for image displays, optical storage and information technology.
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Reflective Quasi-Continuous Metasurface with Continuous Phase Control for Light Focusing. MATERIALS 2021; 14:ma14092147. [PMID: 33922559 PMCID: PMC8122898 DOI: 10.3390/ma14092147] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Revised: 04/14/2021] [Accepted: 04/21/2021] [Indexed: 11/16/2022]
Abstract
Benefitting from the arbitrary and flexible light modulation, metasurface has attracted extensive attention and been demonstrated in different applications. However, most reported metasurface-based devices were normally composed of discrete micro or nano structures, therefore the discretization precision limited the performance of the device, including the focusing efficiency, stray light suppression, and broadband performance. In this work, an all-metallic reflective metasurface consisting of numerous quasi-continuous nanostructures is proposed to realize high-efficiency and broadband focusing. The constructed quasi-continuous metasurface (QCMS) is then verified numerically through electromagnetic simulation, and the numerical results show a higher focusing efficiency and a better stray light suppression effect, compared to a binary-phase-based metalens. Through the same design strategy, a QCMS with the ability to overcome the diffraction limit can also be constructed, and a focal spot with the size of 0.8 times the diffraction limit can be achieved. We expect that this quasi-continuous structure could be utilized to construct other high-performance devices that require continuous phase controls, such as the beam deflector, orbital angle momentum generator, and self-accelerating beam generator.
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Lu X, Guo Y, Pu M, Zhang Y, Li Z, Li X, Ma X, Luo X. Broadband achromatic metasurfaces for sub-diffraction focusing in the visible. OPTICS EXPRESS 2021; 29:5947-5958. [PMID: 33726126 DOI: 10.1364/oe.417036] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Accepted: 01/22/2021] [Indexed: 05/22/2023]
Abstract
Conventional achromatic optical systems are matured to achieve effective chromatic aberration correction and diffraction-limited resolution by the multiple bulky lenses. The emergence of the super-oscillation phenomenon provides an effective method for non-invasive far-field super-resolution imaging. Nevertheless, most super-oscillatory lenses are significantly restricted by the chromatic aberration due to the reliance on delicate interference; on the other hand, most achromatic lenses cannot break the diffraction limit. In this article, a single-layer broadband achromatic metasurface comprising sub-wavelength anisotropic nanostructures has been proposed to achieve sub-diffraction focusing with a focal length of f=60 µm and a diameter of 20 µm in the visible ranging from 400 nm to 700 nm, which are capable of generating sub-diffraction focal spots under the left-handed circularly polarized incident light with arbitrary wavelength in the working bandwidth at the same focal plane. This method may find promising potentials in various applications such as super-resolution color imaging, light field cameras, and machine vision.
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Lu X, Guo Y, Pu M, Xu M, Jin J, Li Z, Li X, Ma X, Luo X. Switchable polarization-multiplexed super-oscillatory metasurfaces for achromatic sub-diffraction focusing. OPTICS EXPRESS 2020; 28:39024-39037. [PMID: 33379460 DOI: 10.1364/oe.413078] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Accepted: 11/20/2020] [Indexed: 06/12/2023]
Abstract
Super-oscillation phenomenon has attracted considerable interests due to its great ability of far-field super-resolution imaging. However, most super-oscillatory lenses were limited by chromatic aberration and single functionality, hence deeply restricting the flexibility of the super-oscillatory devices in practical applications. Here, an achromatic polarization-multiplexed super-oscillatory metasurface has been proposed to realize flexible light field modulations at different colors, i.e. 473 nm (blue), 532 nm (green), and 632.8 nm (red). The super-oscillatory metasurface can achieve achromatic diffraction-limited focusing under x-polarized light illumination and achromatic sub-diffraction focusing under y-polarized light illumination. Furthermore, it can also realize multi-wavelength super-oscillatory achromatic focusing with different super-resolution abilities. The proposed method could simplify the super-resolution optical imaging system and is expected to have widespread applications in color imaging, microscopy, and machine vision.
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Jisha CP, Nolte S, Alberucci A. Polarization-insensitive wavefront shaping using the Pancharatnam-Berry phase. OPTICS LETTERS 2019; 44:5517-5520. [PMID: 31730098 DOI: 10.1364/ol.44.005517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Accepted: 10/21/2019] [Indexed: 06/10/2023]
Abstract
We discuss a method to achieve a polarization-independent modulation of the electromagnetic wavefront based upon the Pancharatnam-Berry phase. When the length of the twisted anisotropic material is equal to the birefringence length (i.e., full-wave plate length), a phase delay proportional to the squared transverse derivative of the twisting angle appears. Physically, the phase delay is associated with the Kapitza effect applied to the Pancharatnam-Berry phase. Our theoretical results are confirmed by finite-difference time-domain (FDTD)-based numerical simulations.
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Zhang X, Tang D, Zhou L, Jiao J, Feng D, Liang G, Guo Y. Polarization-insensitive colorful meta-holography employing anisotropic nanostructures. NANOSCALE 2019; 11:20238-20244. [PMID: 31621736 DOI: 10.1039/c9nr05533a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Benefiting from advances in nanofabrication technology, emerging metasurfaces are promising for compact and wearable multicolor meta-holograms with large fields of view. However, due to the inherent electromagnetic properties of the structures that are used, current multicolor meta-holograms are often sensitive to the incident light polarization, which greatly restricts the application of meta-holography. Here, we took advantage of the amplitude properties of metasurfaces and the off-axis illumination method to carry out experiments involving polarization-insensitive colorful meta-holography with anisotropic nanostructures. With red, green and blue lasers illuminating the meta-hologram along different angles, a polarization-insensitive colorful holographic image was achieved and the disturbance from zero-order diffraction light was essentially eliminated. To the best of our knowledge, the current work was the first time that a polarization-insensitive colorful meta-hologram with anisotropic nanostructures was experimentally demonstrated. We expect our approach to provide promising prospects for the use of metasurfaces in applications such as flat meta-lenses, data storage and virtual/augmented reality.
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Affiliation(s)
- Xiaohu Zhang
- The Key Laboratory of Optoelectronic Technology and Systems of the Education Ministry of China, Chongqing University, Chongqing 400044, China.
| | - Dongliang Tang
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, China
| | - Li Zhou
- The Key Laboratory of Optoelectronic Technology and Systems of the Education Ministry of China, Chongqing University, Chongqing 400044, China.
| | - Jiao Jiao
- Center for Information Geoscience, University of Electronic Science and Technology of China, China
| | - Danqi Feng
- The Key Laboratory of Optoelectronic Technology and Systems of the Education Ministry of China, Chongqing University, Chongqing 400044, China.
| | - Gaofeng Liang
- The Key Laboratory of Optoelectronic Technology and Systems of the Education Ministry of China, Chongqing University, Chongqing 400044, China.
| | - Yongcai Guo
- The Key Laboratory of Optoelectronic Technology and Systems of the Education Ministry of China, Chongqing University, Chongqing 400044, China.
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Tang D, Chen L, Liu J. Visible achromatic super-oscillatory metasurfaces for sub-diffraction focusing. OPTICS EXPRESS 2019; 27:12308-12316. [PMID: 31052773 DOI: 10.1364/oe.27.012308] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2018] [Accepted: 04/03/2019] [Indexed: 06/09/2023]
Abstract
Conventional optical lenses enable precise foci but suffer from the diffraction limit due to the cutoff of spatial frequencies. Development of a super-oscillatory phenomenon offers an alternative approach to realize far-field sub-diffraction focusing. However, most super-oscillatory lenses exhibit a strong dependence on incident wavelengths, resulting in a narrow-band working frequency due to a fragile super-oscillatory field. Here, for the first time, achromatic super-oscillatory metasurfaces (ASOMs) are proposed to simultaneously steer optical fields at visible wavelengths of 473 nm, 532 nm and 632.8 nm and to achieve focusing at the same axial position with a resolution beyond the diffraction limit. These metasurface-based devices provide dispersionless phase profiles so that the material dispersion can be neglected in the optimization process. In addition, the design strategy can effectively circumvent the axial chromatic aberration observed in previously demonstrated metasurfaces. Constructed ASOMs are further verified numerically and simulated results for one ASOM with spot sizes of 0.706, 0.722 and 0.750 times the diffraction limit at the preset plane are consistent with the designs. Furthermore, benefiting from flexible and arbitrary phase modulations of the metasurface, the proposed method gives more freedom for a design of a super-oscillatory field and enables a lightweight, low-cost and compact optical element to replace the bulky doublet/triplet lens in a conventional optical system.
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Chen WT, Zhu AY, Sisler J, Bharwani Z, Capasso F. A broadband achromatic polarization-insensitive metalens consisting of anisotropic nanostructures. Nat Commun 2019; 10:355. [PMID: 30664662 PMCID: PMC6341080 DOI: 10.1038/s41467-019-08305-y] [Citation(s) in RCA: 119] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Accepted: 12/27/2018] [Indexed: 11/27/2022] Open
Abstract
Metasurfaces have attracted widespread attention due to an increasing demand of compact and wearable optical devices. For many applications, polarization-insensitive metasurfaces are highly desirable, and appear to limit the choice of their constituent elements to isotropic nanostructures. This greatly restricts the number of geometric parameters available in design. Here, we demonstrate a polarization-insensitive metalens using otherwise anisotropic nanofins which offer additional control over the dispersion and phase of the output light. As a result, we can render a metalens achromatic and polarization-insensitive across nearly the entire visible spectrum from wavelength λ = 460 nm to 700 nm, while maintaining diffraction-limited performance. The metalens is comprised of just a single layer of TiO2 nanofins and has a numerical aperture of 0.2 with a diameter of 26.4 µm. The generality of our polarization-insensitive design allows it to be implemented in a plethora of other metasurface devices with applications ranging from imaging to virtual/augmented reality. Polarization-insensitive metasurfaces implies limiting the choice of constituent elements to isotropic nanostructures. Here, the authors demonstrate a polarization-insensitive metalens using anisotropic nanofins, allowing achromatic and polarization-insensitive behaviour across the entire visible.
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Affiliation(s)
- Wei Ting Chen
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, 02138, USA.
| | - Alexander Y Zhu
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, 02138, USA
| | - Jared Sisler
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, 02138, USA.,University of Waterloo, Waterloo, ON, N2L 3G1, Canada
| | - Zameer Bharwani
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, 02138, USA.,University of Waterloo, Waterloo, ON, N2L 3G1, Canada
| | - Federico Capasso
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, 02138, USA.
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