Open Access
Add to BibSonomy
Abstract
Metasurfaces are artificially engineered ultrathin photonic components that can be freely designed to exhibit unprecedented capabilities of highly-efficient electromagnetic wave manipulation. The ever-growing demand for miniaturized photonic devices for emerging applications, like imaging, spectroscopy, biosensing, and quantum information processing, consistently requires broadband multifunctional and highly-efficient meta-devices. Recent years have witnessed tremendous advancements in metasurfaces; however, investigating the novel platform to realize broadband metasurfaces that integrate multiple functionalities in a single-layered structure would be an obvious technological extension. Here, we present a broadband single-cell-driven multifunctional metasurface platform capable of manipulating electromagnetic waves over a wide range of visible wavelengths (475−650 nm). A lossless zinc sulfide material exhibiting a sufficiently large refractive index and negligible extension coefficient across the visible spectrum is exploited to demonstrate the state-of-the-art meta-devices. Furthermore, a well-known spin-decoupling technique is implemented to multiplex different optical phenomena into a single-cell-driven structure. For proof of the concept, we demonstrate two meta-devices that provide transverse and longitudinal splitting of different optical phenomena for the visible wavelengths. The presented zinc sulfide material and unique design philosophy to achieve broadband multifunctional meta-devices may find potential applications in polarization and dispersion analyzers, sensing, optical communication, and many more.
© 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
1. Introduction
Metasurfaces, the planar version of three-dimensional metamaterials, generated significant excitement and considerable interest due to their reduced footprints, exceptional wavefront engineering capabilities, and batch production opportunities [1–3]. Metasurfaces, consisting of an ultrathin layer of judiciously engineered building blocks, serve as an alternative to replace the traditional bulky optical components and provide unprecedented avenues for bridging the gap between fundamental research and device-level integration of these artificially engineered structures [4–6]. The versatile capability of the metasurfaces to tailor the light’s quintessential properties like amplitude, phase, and polarization enables the realization of exotic optical phenomena and applications, including flat lenses [7–9], structured beam generators [10–15], high-resolution holograms [16–22], surface plasmon couplers [23], and many other interfaces [24–29]. Recent years are witnessed significant development of the metasurfaces; however, most of the designed metasurfaces are operational for a single wavelength or multiple bands [30–33]. Furthermore, these metasurfaces are also limited in functionalities because integrating multiple optical phenomena into a single meta-device often requires a complicated or multilayer design technique [34–37]. Although multilayer metasurfaces provide an extra degree of freedom by introducing more versatility and flexibility to the design approach, again, the large interlayer spacing and the precise alignment have road-blocked their integration into real-life applications [38,39].
It is well understood that through the selection of appropriate material and careful design of constituent nanoantennas of the metasurfaces, the amplitude, phase, and polarization of the light can be engineered to achieve the desired optical properties [2]. Optical metasurfaces consisting of subwavelength plasmonic scatterers have seen considerable growth due to the miniaturized structure, efficient hot electron generation, and high optical confinement from microwave to near-infrared regimes [40,41]. However, significant material’s intrinsic Ohmic losses deteriorated their performance in visible and ultraviolet spectrums [42]. To circumvent the plasmonic-related issues, different high-index dielectric materials such as silicon (Si), hydrogenated amorphous silicon (a-Si:H), titanium dioxide (TiO2), gallium nitride (GaN), and silicon nitride (Si3N4) have been proposed to demonstrate highly-efficient all-dielectric metasurfaces at infrared and visible spectrums [43–46]. However, most of the reported materials exhibit meager efficiency for smaller wavelengths of the visible spectrum due to the materials’ inter-band transitions. Thus far, very few materials are reported that exhibit visible transparent behavior, hence, necessitating hunting for alternative materials to realize highly-efficient broadband visible metasurfaces.
To achieve full control of the scattered light, two approaches, namely, propagation and the Pancharatnam-Berry (PB) phase, have been extensively studied and utilized [4]. The propagation phase mechanism relies on the indexed waveguide theory, where the effective refractive index of the propagating mode is altered by varying the physical dimensions of the nanoantenna [5]. The lateral can be well-understood through Eq. (1).
where ${\lambda _d}$ represents the design wavelength, ${n_{eff}}$ is the effective refractive index of the dominant mode, and H is the thickness of the nanoantenna. However, this technique allows for independent phase distributions under the two orthogonal handedness of linearly polarized light. The major drawback of the propagation phase-based metasurfaces is that only 50% efficiency can be capped for a certain polarization handedness [47], thus hindering their application as multifunctional and broadband metasurfaces. Meanwhile, the PB phase enables the polarization-multiplexed design of metasurfaces that exhibit unique phase distribution under the opposite handedness of the circularly polarized light. The required asymmetric nanoantenna is designed in a way to act as a half-wave plate $({|{{\phi_x} - {\phi_y}} |= \pi } )$, that is then in-plane rotated to achieve the spatial phase distribution of $\phi ({x,y} )= 2\theta ({x,y} ),$ where $\theta $ specifies the in-plane rotational angle of the building block.Under the unique handedness of the circularly polarized light, the in-plane rotation of the optimized nanoantenna from $0 - \pi $ can provide a complete phase profile that can be tailored linearly from $0 - 2\pi $. The major advantage of the PB phase is that, due to the symmetry, the acquired phase profile for right-hand circularly polarized (RCP) light will be opposite for left-hand circularly polarized (LCP) light, that is, ${\phi _{RCP}}({x,y} )={-} {\phi _{LCP}}({x,y} )$. However, the multiplexed optical phenomena under RCP and LCP incidence are locked together. The spin-decoupling technique provides a convenient method of multiplexing numerous unique information into a single structure that can be decoupled by impinging the circularly polarized light of opposite-handedness. Furthermore, the inherent wavelength-independent behavior of the PB phase can be further optimized to attain an extended broadband response. Collectively, by selecting appropriate dielectric material, carefully optimizing the nanoantennas as half-wave plates, and merging the multiple phase profile through the spin-decoupling technique, one can realize a highly efficient, broadband, multifunctional metasurface platform for any range of wavelengths.
In this work, we take the same route to present a highly efficient, broadband, multifunctional metasurface platform for the visible spectrum. The designed metasurfaces consist of half-wave plates made of visible-transparent zinc sulfide (ZnS) material and merge the multiple information via the spin-decoupling technique. The presented dielectric material can be deposited on a glass substrate and possesses a sufficiently high refractive index (n) and a negligible absorption $({\textrm{k} \cong 0} )$ across the visible spectrum enabling us to design highly efficient and broadband metasurfaces [48]. A $650\,\textrm{nm}$ tall nanoantenna of ZnS is numerically optimized in a way to work as a half-wave plate that exhibits maximum possible cross-polarization transmission efficiency across the targeted visible band $({475 - 650\,\textrm{nm}} )$. The metasurface design methodology utilizes the spin-decoupling mechanism to integrate multiple functionalities into a single-layered meta-device. For proof of concept, we have designed two such metasurfaces that integrate phase profiles of four metalenses each, which are then demonstrated at the same focal planes but at different positions and different focal planes along the propagation axis, respectively. Such kind of miniaturized metalenses may have a significant impact on numerous nanophotonics applications, from lab-based microscopy to consumer-level devices. The working principle of the proposed highly-efficient broadband multifunctional metasurfaces is presented in Fig. 1, where the metasurface is illuminated from the substrate side, and the scattered light is apprehended at the output (transmission) side.
Fig. 1. (a) Perspective view, (b) Working principle of multifunctional and multidimensional metasurfaces. (c) and (d) top view of the unit cell.
2. Material and method
The proposed metasurface platform consists of ZnS-based nanoantennas of unique physical dimensions but different orientations on the flat substrate. The major advantage of the presented platform is its robust and straightforward design scheme, where all the integrated optical phenomena can be engineered simultaneously through a single set of geometric parameters. The real ($\textrm{n}$) and imaginary ($\textrm{k}$) parts of the complex refractive index of ZnS material are presented in Fig. 2(a) [49], which exhibits approximately zero extinction coefficient $({\textrm{k} \approx 0} )$ and sufficient refractive index $({2.31 < \textrm{n} < 2.43} )$ across the targeted visible spectrum ($475\,\textrm{nm}$ to $650\,\textrm{nm}$). The sufficient large refractive index allows strong optical confinement within the nanoantenna, thus eliminating the possible crosstalk between adjacent elements. Through the indexed waveguide theory [5], the thickness of the ZnS nanoantenna is selected as 650 nm to achieve complete $({0 - 2\pi } )$ phase distribution. The numerical optimization of the nanoantenna is carried out through FDTD Solution 2022 R1.4 Finite Difference IDE from Ansys Lumerical Inc. The optimum value of the period is selected in a way that allows the maximum constructive interference of the diffracted light. In our case, numerical optimization reveals the $\textrm{P} = 435\,\textrm{nm}$ ensuring the maximum possible transmission efficiency.
Fig. 2. Complex refractive index and numerical (optimization of the fundamental building block. (a) Real ($\textrm{n}$) and imaginary ($\textrm{k}$) parts of the complex refractive index of zinc sulfide [49]. (b) Transmission coefficients of 650 nm tall half-wave plate with optimized dimensions as $\textrm{L} = 260\,\textrm{nm}$ and $\textrm{W} = 110\,\textrm{nm}$ ensure the average transmission efficiency ${\mathrm{\eta }_{\textrm{Avg}}} = 79.92\mathrm{\%}$ in the desired band. (c) Rotation angle vs. phase distribution of the nanoantenna for specific wavelengths.
For fixed values of period and thickness, the width and length of the nanoantenna are swept from $({70 < \textrm{W} < 150} )$ and $({220 < \textrm{L} < 300} )$. The unit cell is illuminated with the LCP light of $532\,\textrm{nm}$, and the scattered light with opposite polarization is captured and investigated. For the optimized dimension of nanoantenna as $\textrm{L} = 260\,\textrm{nm}$ and $\textrm{W} = 110\,\textrm{nm}$, Fig. 2(b) describes the transmission spectra of co- and cross-polarized light vs. wavelength. The pink straight line represents the average maximum transmission efficiency whereas the green line indicates the average transmission efficiency ${\mathrm{\eta }_{\textrm{Avg}}} = 79.92\mathrm{\%}$ for the selected dimensions of the nanoantenna. The blue line indicates the transmission intensity of the co-polarized light. To further ensure the functionality of the optimized nanoantennas as half-wave plates, the nanoantenna rotated in-plane from $0 - {180^\textrm{o}}$, and the phase distribution of the cross-polarized light is analyzed and described in Fig. 2(c). The detailed numerical optimization results for different wavelengths are presented in Fig. 3, which shows that the selected dimension of the nanoantenna provides near-maximum cross-polarized and minimum co-polarized transmission efficiency. Figure 3(a1–d1) describes the transmission efficiency of the cross-polarized light and Fig. 3(a2–d2) presents the intensity of co-polarized light. The dashed lines and steric indicate the dimensions of the optimized nanoantenna.
Fig. 3. Polarization conversion efficiency for selected wavelength in the targeted visible band $({475 - 650\,\textrm{nm}} )$. (a1–d1) Cross-polarization conversion efficiency. (a2–d2) Co-polarization conversion efficiency. White steric indicates the optimized dimensions of the nanoantenna as $\textrm{L} = 260\,\textrm{nm}$ and $\textrm{W} = 110\,\textrm{nm}$. The average transmission efficiency of the cross-polarization field is ${\mathrm{\eta }_{\textrm{Avg}}} = 79.92\mathrm{\%}$ in the desired band.
By considering the rectangular-shaped nanoantenna with ordinary and extraordinary axes, the coefficients of scattered light under linear polarization can be represented as to and te, respectively. According to the PB phase mechanism, as the nanoantenna is oriented at an angle $\theta $, Jones matrix formalism can be used to determine these coefficients [50]
Through some mathematical manipulation, the linear basis can be transformed into a circular basis and the Jones matrix for circular polarization can be described as [51]
In order to demonstrate the multifunctional capabilities of the designed metasurfaces, we exploit the spin-decoupling mechanism that allows the integration of multiple optical phenomena into a single meta-device. This is possible by taking advantage of the spin-dependent property of the PB phase that exhibits the opposite phase profiles to RCP and LCP incidence. The incident plane wave can be focused at the desired focal plane $(f )$ by spatially distributing the nanoantennas according to the phase profile given in Eq. (4)
3. Results and discussion
For proof of the concept, we design and simulate two metasurfaces that work as highly-efficient broadband multidimensional and multifunctional meta-devices in the visible regime. First designed structure encodes the phase profiles of four metalenses and generates four different off-axis focused spots at the defined focal plane. According to Eq. (6), the phase profiles of two metalenses are encoded for LCP light incorporating the lateral offset along the $x$-axis and the rest of the two phase profiles are encoded for RCP light having lateral offset along the $y$-axis. Using Eq. (7), these phase profiles are multiplexed and encoded to design the metasurface. Initially, the designed metasurface is simulated for the demonstration of broadband operation. A linearly polarized light with different visible wavelengths ($488\,\textrm{nm},\,532\textrm{nm},\,594\,\textrm{nm},\,\textrm{and}\,633\,\textrm{nm}$) impinges on the metasurface that produces transverse symmetric four focused spots at different positions of the focal plane. Here, for overall $25 \times 25\,\mathrm{\mu }{\textrm{m}^2}$ metasurface size, the offset value is set as ${x_m} = {y_m} = 8\; \mathrm{\mu}\textrm{m}$ and the focal length is taken as $f = 25\,\mathrm{\mu}\textrm{m}$.
Figure 4(a1–a4) describes the electric field intensity profile captured by the longitudinal (XZ) monitors for specific wavelengths of the visible regime. The gradual downward shifting of the focal plane with the increment in the wavelength indicates the expected dispersive behavior of the dielectric material. Figure 4(b1–b4) illustrates the intensity profile at the transverse (XY) plane (focal plane) that exhibits four high-intensity points at $({ \pm 8\,\mathrm{\mu}\textrm{m},0} )$ and $({0,\, \pm 8\,\mathrm{\mu}\textrm{m}} )$, respectively. The dotted boxes enclose the magnified version of one of the four focused spots. The excellent broadband off-axis focusing capability of the presented multifunctional metasurfaces authenticates the suitability of the proposed material and design methodology for the visible spectrum.
Fig. 4. Simulation response of the broadband multidimensional metasurface. (a1–a4) describes the transmission profiles captured by the longitudinal (XZ) monitors. (b1–b4) Represents the intensity profile at the transverse (XY) plane. The inset shows the magnified version of one focusing spot.
The spin-decoupling capability of the designed metasurface is verified for single wavelength $({\mathrm{\lambda } = 532\,\textrm{nm}} )$. As per the design strategy presented in Eqs. (6) and (7), the phase profiles of two metalenses with a lateral offset along the $x$-axis are encoded for LCP light while the other two phase profiles with a lateral offset along the $y$-axis are encoded for RCP light. Figure 5 illustrates the behavior of diffracted light under different polarization states of the input light. The focusing points under LCP and RCP incidence are displaced along the $x$- and $y$-axis, respectively. By imping the LP light of the desired wavelength, the spin-dependent all four focus spots appear at the transverse plane. High-intensity focusing of multiple metalenses ensures negligible coupling and cross-talk between different phase profiles.
Fig. 5. Verification of spin-decoupling of multifunctional metasurface for wavelength $532\,\textrm{nm}$. (a1), (b1) Transverse and longitudinal profile under the LCP light. (a2), (b2) same transmission behavior under RCP light. (a3), (b3) Under the illumination of LP light. The magnified version of one focus spot is presented in the dashed box of (b3).
Multifocal optical components are extremely required for imaging and focusing in 3D applications. Although a couple of multifocal metasurfaces have been realized for single wavelengths of different spectra [35,53], it is quite challenging to demonstrate such highly-efficient multifunctional metasurfaces for broadband wavelengths. The expected material aberration, wavelength-dependent phase accumulation, and the requirement of highly-precise phase modulation are the major hurdles that need to be addressed. In comparison to the existing work on multifocal metasurfaces, we demonstrate a multifunctional/multifocal metasurface that generates four different focused spots at different focal planes over a broad range of visible wavelengths. The spin-decoupling mechanism provides a superior degree of freedom to integrate multiple functionalities into a single meta-device that can be isolated by illuminating input light of different polarization states.
Here, we designed a multifocal metasurface capable of longitudinal splitting the four focusing points. According to Eqs. (7) and (8), phase profiles of four metalenses with different focal planes are merged and encoded into the metasurface. For this design, different focal planes are chosen along the propagation axis as $15\,\mathrm{\mu}\textrm{m},\,25\,\mathrm{\mu}\textrm{m},\,35\,\mathrm{\mu}\textrm{m},\,\textrm{and}\,45\,\mathrm{\mu}\textrm{m}$. Initially, the designed metasurface is simulated for broadband operation by impinging the LP incident light of selected wavelengths and Fig. 6 describes the simulated electric field intensity of the multifocal metasurface. Figure 6 (a) describes the simulated electric field profile along the longitudinal (XZ) planes for wavelengths $\mathrm{\lambda } = 488\,\textrm{nm}$ where four focal spots at different planes are observed. Figure 6 (b–d) describes the same behavior but for other wavelengths as $\mathrm{\lambda } = 532,\,594,\,\textrm{and}\,633\,\textrm{nm}$. The red dashed line indicates the reference focusing plane and also illustrates the downward shift of the focal plane due to the dispersive behavior of the dielectric material. The availability of extra information and non-uniform field distribution in multi-focusing results may arise due to the possible cross-talk and interference as focusing points are close enough. This issue can be resolved by increasing the distance between the focal planes, ultimately requiring more computational power and simulation memory. The transverse (XY) view of each focal plane is presented in Fig. 6(a1–a4), (b1–b4), (c1–c4), and (d1–d4) for specific wavelengths $\mathrm{\lambda } = 488,\,532,\,594,\,\textrm{and}\,633\,\textrm{nm}$ of the input light.
Fig. 6. Numerically simulated profiles of a broadband multifocal metasurface. (a–d) Longitudinal profile of the scattered light from the metasurface. (a1–a4) Transverse view of the four focal spots for $\mathrm{\lambda } = 488\,\textrm{nm}$. (b1–b4), (c1–c4), and (d1–d4) Transverse view of the four focal spots for $\mathrm{\lambda } = 532,\,594\,\textrm{and}\,633\,\textrm{nm}$, respectively.
The spin de-coupling capability of the presented multifocal metasurface is verified by illuminating the designed metasurface with the incident light of different polarizations. For this purpose, phase profiles of two metalenses with focal planes $15\,\mathrm{\mu}\textrm{m}\,\textrm{and}\;25\,\mathrm{\mu}\textrm{m}$, respectively, are integrated for LCP light. The other two phase profiles of metalenses with focal planes $35\,\mathrm{\mu}\textrm{m}\,\textrm{and}\,45\,\mathrm{\mu}\textrm{m}$, respectively, are integrated for RCP light. The numerically simulated results of the designed multifocal metasurface are presented in Fig. 7, which illustrates the achievement of spin-dependent transverse focusing. Figure 7(a) and (a1–a4) describe the simulated electric field intensity profile by illuminating the metasurface with LCP light of wavelength $\mathrm{\lambda } = 532\; \textrm{nm}$. It is observed that under LCP incidence, only two focal points at $15\,\mathrm{\mu}\textrm{m}\,\textrm{and}\,25\,\mathrm{\mu}\textrm{m}$ appears whereas the other two focal plane exhibit approximately negligible electric field intensity. By incident light with RCP polarization, two focal spots at $35\,\mathrm{\mu}\textrm{m}\,\textrm{and}\,45\,\mathrm{\mu}\textrm{m}$ are observed and presented in Fig. 7(b) and (b1–b4). As described earlier that LP light is the combination of LCP and RCP light, so by impinging the LP light, all four longitudinal displaced focusing points appear at the desired focal plane as indicated by Fig. 7(c) and (c1–c4).
Fig. 7. Spin-decoupling verification of multifocal metasurface for visible wavelength $532\,\textrm{nm}$. . (a) and (a1–a4) Under the LCP illumination. (b) and (b1–b4) The same behavior but under RCP incidence. (c) and (c1–c4) illustrates the simulated behavior under LP incidence.
4. Conclusion
In conclusion, we demonstrate a unique design approach to realize a highly-efficient broadband multifunctional and multidimensional metasurface platform for the visible domain. The zinc sulfide is presented as a visible-transparent material ensuring the descent average transmission efficiency ${\eta _{Avg}} = 79.92\%$ across the visible spectrum. The designed multidimensional and multifocal metasurfaces are capable of achieving spin-multiplexed transverse and longitudinal focusing. The focusing positions, focal planes, and spin dependence can be engineered conveniently and flexibly during the design process. Specifically, we design and numerically simulate two meta-devices that integrate unique phase profiles for LCP and RCP light. The broadband functionality of both metasurfaces is verified by impinging the visible light of selected wavelengths as $\lambda = 488,\; 532,\; 594,\; and\; 633\; nm$. The spin-decoupling ability is proved by observing unique behavior for LCP, RCP, and LP input light. The simulated results illustrate the excellent capability of the proposed structures to work as broadband, multidimensional and multifunctional meta-devices. Such straightforward design techniques can be extended for other materials and frequency bands to design broadband, multifunctional and multidimensional meta-devices and more complicated functionalities can be achieved
Funding
King Abdullah University of Science and Technology (Innovative Technologies Laboratories).
Acknowledgments
The authors would like to acknowledge research funding to the Innovative Technologies Laboratories from King Abdullah University of Science and Technology (KAUST).
Disclosures
The authors declare no conflicts of interest
Data availability
Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.
References
1. N. Yu, P. Genevet, M. A. Kats, F. Aieta, J.-P. Tetienne, F. Capasso, and Z. Gaburro, “Light propagation with phase discontinuities: generalized laws of reflection and refraction,” Science 334(6054), 333–337 (2011). [CrossRef]
2. N. Yu and F. Capasso, “Flat optics with designer metasurfaces,” Nat. Mater. 13(2), 139–150 (2014). [CrossRef]
3. M. Khorasaninejad and F. Capasso, “Metalenses: Versatile multifunctional photonic components,” Science 358(6367), 1–8 (2017). [CrossRef]
4. R. C. Devlin, M. Khorasaninejad, W. T. Chen, and F. Capasso, “Broadband high-efficiency dielectric metasurfaces for the visible spectrum,” Proc. Natl. Acad. Sci. 113(38), 10473–10478 (2016). [CrossRef]
5. N. Mahmood, I. Kim, M. Q. Mehmood, H. Jeong, A. Akbar, D. Lee, M. Saleem, M. Zubair, M. S. Anwar, F. A. Tahir, and J. Rho, “Polarisation insensitive multifunctional metasurfaces based on all-dielectric nanowaveguides,” Nanoscale 10(38), 18323–18330 (2018). [CrossRef]
6. N. Mahmood, H. Jeong, I. Kim, M. Q. Mehmood, M. Zubair, A. Akbar, M. Saleem, M. S. Anwar, F. A. Tahir, and J. Rho, “Twisted non-diffracting beams through all dielectric meta-axicons,” Nanoscale 11(43), 20571–20578 (2019). [CrossRef]
7. Nanfang Yu, P. Genevet, F. Aieta, M. A. Kats, R. Blanchard, G. Aoust, J.-P. Tetienne, Z. Gaburro, and F. Capasso, “Flat optics: controlling wavefronts with optical antenna metasurfaces,” IEEE J. Sel. Top. Quantum Electron. 19, 1–23 (2013). [CrossRef]
8. M. Khorasaninejad, Y. Zhu, C. Roques-carmes, J. Oh, I. Mishra, R. C. Devlin, and F. Capasso, “Polarization-insensitive metalenses at visible wavelengths,” Nano Lett. 16(11), 7229–7234 (2016). [CrossRef]
9. E. Arbabi, A. Arbabi, S. M. Kamali, Y. Horie, and A. Faraon, “Multiwavelength polarization-insensitive lenses based on dielectric metasurfaces with meta-molecules,” Optica 3(6), 628–633 (2016). [CrossRef]
10. M. A. Ansari, M. H. Waseem, I. Kim, N. Mahmood, H. Jeong, F. A. Tahir, T. Tauqeer, M. Q. Mehmood, and J. Rho, “Highly efficient visible hologram through dielectric metasurface,” in J. Phys.: Conf. Ser. (Institute of Physics Publishing, 2018), Vol. 1092, pp. 1–4.
11. S. Noureen, H. Ahmed, N. Mahmood, M. Zubair, and M. Q. Mehmood, “Amplitude and phase engineered all-dielectric metasurface for finite energy self-accelerating airy beam generation,” in SPIE Nanoscience + Engineering (2020), Vol. 1146706, p. 5.
12. Z. Jin, D. Janoschka, J. Deng, L. Ge, P. Dreher, B. Frank, G. Hu, J. Ni, Y. Yang, J. Li, C. Yu, D. Lei, G. Li, S. Xiao, S. Mei, H. Giessen, F. M. zu Heringdorf, and C.-W. Qiu, “Phyllotaxis-inspired nanosieves with multiplexed orbital angular momentum,” eLight 1(1), 1–11 (2021). [CrossRef]
13. M. D. Shafqat, N. Mahmood, M. Zubair, M. Q. Mehmood, and Y. Massoud, “Highly efficient perfect vortex beams generation based on all-dielectric metasurface for ultraviolet light,” Nanomaterials 12(19), 1–13 (2022). [CrossRef]
14. H. Ahmed, H. Kim, Y. Zhang, Y. Intaravanne, J. Jang, J. Rho, S. Chen, and X. Chen, “Optical metasurfaces for generating and manipulating optical vortex beams,” Nanophotonics 11(5), 941–956 (2022). [CrossRef]
15. R. M. H. Bilal, M. A. Saeed, M. A. Naveed, M. Zubair, M. Q. Mehmood, and Y. Massoud, “Nickel-based high-bandwidth nanostructured metamaterial absorber for visible and infrared spectrum,” Nanomaterials 12(19), 1–13 (2022). [CrossRef]
16. G. Zheng, H. Mühlenbernd, M. Kenney, G. Li, T. Zentgraf, and S. Zhang, “Metasurface holograms reaching 80% efficiency,” Nat. Nanotechnol. 10(4), 308–312 (2015). [CrossRef]
17. P. Genevet and F. Capasso, “Holographic optical metasurfaces: a review of current progress,” Rep. Prog. Phys. 78(2), 24401 (2015). [CrossRef]
18. M. A. Ansari, I. Kim, D. Lee, M. H. Waseem, M. Zubair, N. Mahmood, T. Badloe, S. Yerci, T. Tauqeer, M. Q. Mehmood, and J. Rho, “A spin-encoded all-dielectric metahologram for visible light,” Laser Photonics Rev. 13, 1–9 (2019). [CrossRef]
19. N. Mahmood, M. Q. Mehmood, and F. A. Tahir, “Diamond step-index nanowaveguide to structure light efficiently in near and deep ultraviolet regimes,” Sci. Rep. 10, 1–10 (2020). [CrossRef]
20. H. S. Khaliq, J. Kim, T. Naeem, K. Riaz, T. Badloe, J. Seong, J. Akbar, M. Zubair, M. Q. Mehmood, Y. Massoud, and J. Rho, “Broadband chiro-optical effects for futuristic meta-holographic displays,” Adv. Opt. Mater. 10(22), 1–8 (2022). [CrossRef]
21. M. A. Naveed, J. Kim, I. Javed, M. A. Ansari, J. Seong, Y. Massoud, T. Badloe, I. Kim, K. Riaz, M. Zubair, M. Q. Mehmood, and J. Rho, “Novel spin-decoupling strategy in liquid crystal-integrated metasurfaces for interactive metadisplays,” Adv. Opt. Mater. 10, 1–9 (2022). [CrossRef]
22. I. Javed, J. Kim, M. A. Naveed, D. K. Oh, D. Jeon, I. Kim, M. Zubair, Y. Massoud, M. Q. Mehmood, and J. Rho, “Broad-band polarization-insensitive metasurface holography with a single-phase map,” ACS Appl. Mater. Interfaces 14(31), 36019–36026 (2022). [CrossRef]
23. L. Huang, X. Chen, H. Mühlenbernd, G. Li, B. Bai, Q. Tan, G. Jin, T. Zentgraf, and S. Zhang, “Dispersionless phase discontinuities for controlling light propagation,” Nano Lett. 12(11), 5750–5755 (2012). [CrossRef]
24. N. Mahmood, M. Q. Mehmood, I. Kim, H. Jeong, F. A. Tahir, and J. Rho, “Light manipulation at compact scale via all–dielectric metasurfaces,” in Metamaterials (2018), pp. 474–476.
25. N. Mahmood, M. Q. Q. Mehmood, I. Lim, M. A. Ansari, T. Tauqeer, F. A. Tahir, and J. Rho, “Manipulating twisted light beam through all-dielectric metasurfaces,” in High Contrast Metastructures VIII, SPIE OPTO (SPIE-Intl Soc Optical Eng, 2019), pp. 1–8.
26. S. Ijaz, A. S. Rana, Z. Ahmad, M. Zubair, Y. Massoud, and M. Q. Mehmood, “The dawn of metadevices: from contemporary designs to exotic applications,” Adv. Devices Instrum. 2022, 1–24 (2022). [CrossRef]
27. M. A. Abbas, J. Kim, A. S. Rana, I. Kim, B. Rehman, Z. Ahmad, Y. Massoud, J. Seong, T. Badloe, K. Park, M. Q. Mehmood, M. Zubair, and J. Rho, “Nanostructured chromium-based broadband absorbers and emitters to realize thermally stable solar thermophotovoltaic systems,” Nanoscale 14(17), 6425–6436 (2022). [CrossRef]
28. Q. Ma, W. Gao, Q. Xiao, L. Ding, T. Gao, Y. Zhou, X. Gao, T. Yan, C. Liu, Z. Gu, X. Kong, Q. H. Abbasi, L. Li, C.-W. Qiu, Y. Li, and T. J. Cui, “Directly wireless communication of human minds via non-invasive brain-computer-metasurface platform,” eLight 2(1), 1–3 (2022). [CrossRef]
29. L. Li, H. Zhao, C. Liu, L. Li, and T. J. Cui, “Intelligent metasurfaces: control, communication and computing,” eLight 2(1), 7 (2022). [CrossRef]
30. N. Mahmood, H. Jeong, F. A. Tahir, M. Q. Mehmood, J. Rho, and I. Kim, “Micron-scale light structuring via flat nanodevices,” in SPIE Photonics Europe (2018), Vol. 10671, pp. 1–6.
31. J. Kim, D. Jeon, J. Seong, T. Badloe, N. Jeon, G. Kim, J. Kim, S. Baek, J. L. Lee, and J. Rho, “Photonic encryption platform via dual-band vectorial metaholograms in the ultraviolet and visible,” ACS Nano 16(3), 3546–3553 (2022). [CrossRef]
32. C.-T. Chou Chao, Y.-F. Chou Chau, and H.-P. Chiang, “Biosensing on a plasmonic dual-band perfect absorber using intersection nanostructure,” ACS Omega 7(1), 1139–1149 (2022). [CrossRef]
33. D. Lee, S. So, G. Hu, M. Kim, T. Badloe, H. Cho, J. Kim, H. Kim, C.-W. Qiu, and J. Rho, “Hyperbolic metamaterials: fusing artificial structures to natural 2D materials,” eLight 2(1), 1–23 (2022). [CrossRef]
34. Y. Liu, L. Chen, C. Zhou, K. Guo, X. Wang, Y. Hong, X. Yang, Z. Wei, and H. Liu, “Theoretical study on generation of multidimensional focused and vector vortex beams via all-dielectric spin-multiplexed metasurface,” Nanomaterials 12(4), 580–593 (2022). [CrossRef]
35. C. Zheng, J. Li, Z. Yue, J. Li, J. Liu, G. Wang, S. Wang, Y. Zhang, Y. Zhang, and J. Yao, “All-dielectric trifunctional metasurface capable of independent amplitude and phase modulation,” Laser Photonics Rev. 16, 12–25 (2022). [CrossRef]
36. K. Du, H. Barkaoui, X. Zhang, L. Jin, Q. Song, and S. Xiao, “Optical metasurfaces towards multifunctionality and tunability,” Nanophotonics 11(9), 1761–1781 (2022). [CrossRef]
37. . . W. Zhu, Y. Fan, R. Yang, G. Geng, Q. Fu, C. Gu, J. Li, and F. Zhang, “Polarization-multiplexed silicon metasurfaces for multi-channel visible light modulation,” Adv. Funct. Mater. 32, 1–7 (2022). [CrossRef]
38. Q. Zheng, Y. Li, J. Zhang, H. Ma, J. Wang, Y. Pang, Y. Han, S. Sui, Y. Shen, H. Chen, and S. Qu, “Wideband, wide-angle coding phase gradient metasurfaces based on Pancharatnam-Berry phase,” Sci. Rep. 7(1), 43543 (2017). [CrossRef]
39. Y. Zhou, I. I. Kravchenko, H. Wang, J. R. Nolen, G. Gu, and J. Valentine, “Multilayer noninteracting dielectric metasurfaces for multiwavelength metaoptics,” Nano Lett. 18(12), 7529–7537 (2018). [CrossRef]
40. L. Huang, X. Chen, H. Mu, H. Zhang, S. Chen, B. Bai, Q. Tan, G. Jin, K. Cheah, C. Qiu, J. Li, T. Zentgraf, and S. Zhang, “Three-dimensional optical holography using a plasmonic metasurface,” Nat. Commun. 4(1), 1–8 (2013). [CrossRef]
41. N. Meinzer, W. L. Barnes, and I. R. Hooper, “Plasmonic meta-atoms and metasurfaces,” Nat. Photonics 8(12), 889–898 (2014). [CrossRef]
42. J. B. Khurgin, “How to deal with the loss in plasmonics and metamaterials,” Nat. Nanotechnol. 10(1), 2–6 (2015). [CrossRef]
43. K. Huang, Z. Dong, S. Mei, L. Zhang, Y. Liu, and H. Liu, “Silicon multi-meta-holograms for the broadband visible light,” Laser Photonics Rev. 10(3), 500–509 (2016). [CrossRef]
44. B. H. Chen, P. C. Wu, V.-C. Su, Y.-C. Lai, C. H. Chu, I. C. Lee, J.-W. Chen, Y. H. Chen, Y.-C. Lan, C.-H. Kuan, and D. P. Tsai, “GaN metalens for pixel-level full-color routing at visible light,” Nano Lett. 17(10), 6345–6352 (2017). [CrossRef]
45. I. Kim, R. J. Martins, J. Jang, T. Badloe, S. Khadir, H.-Y. Jung, H. Kim, J. Kim, P. Genevet, and J. Rho, “Nanophotonics for light detection and ranging technology,” Nat. Nanotechnol. 16(5), 508–524 (2021). [CrossRef]
46. M. A. Naveed, M. A. Ansari, I. Kim, T. Badloe, J. Kim, D. K. Oh, K. Riaz, T. Tauqeer, U. Younis, M. Saleem, M. S. Anwar, M. Zubair, M. Q. Mehmood, and J. Rho, “Optical spin-symmetry breaking for high-efficiency directional helicity-multiplexed metaholograms,” Microsyst. Nanoeng. 7(1), 1–9 (2021). [CrossRef]
47. L. Huang, S. Zhang, and T. Zentgraf, “Metasurface holography: from fundamentals to applications,” Nanophotonics 7(6), 1169–1190 (2018). [CrossRef]
48. P. O. Offor, B. A. Okorie, F. I. Ezema, V. S. Aigbodion, C. C. Daniel-Mkpume, and A. D. Omah, “Synthesis and characterization of nanocrystalline zinc sulphide thin films by chemical spray pyrolysis,” J. Alloys Compd. 650, 381–385 (2015). [CrossRef]
49. M. Debenham, “Refractive indices of zinc sulfide in the 0.405–13-µm wavelength range,” Appl. Opt. 23(14), 2238–2239 (1984). [CrossRef]
50. H.-H. Hsiao, C. H. Chu, and D. P. Tsai, “Fundamentals and applications of metasurfaces,” Small Methods 1(4), 1600064 (2017). [CrossRef]
51. M. Kang, T. Feng, H.-T. Wang, and J. Li, “Wave front engineering from an array of thin aperture antennas,” Opt. Express 20(14), 15882–15890 (2012). [CrossRef]
52. K. Ou, G. Li, T. Li, H. Yang, F. Yu, J. Chen, Z. Zhao, G. Cao, X. Chen, and W. Lu, “High efficiency focusing vortex generation and detection with polarization-insensitive dielectric metasurfaces,” Nanoscale 10(40), 19154–19161 (2018). [CrossRef]
53. H.-X. Xu, S. Tang, T. Cai, S. Sun, Q. He, and L. Zhou, Multifunctional Metasurfaces: Design Principles and Device Realizations (Springer, 2021), Vol. 2.
