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Metamaterials|13 Article(s)
High-efficiency broadband polarization-independent superscatterer using conformal metasurfaces
He-Xiu Xu, Shiwei Tang, Chen Sun, Lianlin Li, Haiwen Liu, Xinmi Yang, Fang Yuan, and Yunming Sun
Safe detection of an arbitrarily shaped platform is critical for survivability, rescue, or navigation safety in a remote region. Metasurfaces afford great potential due to their strong electromagnetic (EM) wave control. However, studies have mainly focused on the physics and design of metasurfaces on planar plates, which does not satisfy the current requirements of aerodynamics and aesthetics. Herein, we propose a sophisticated strategy to design a metasurface that can wrap over arbitrarily shaped objects with moderate curvature on which optical aberrations are commonly introduced. By designing each meta-atom on the basis of the required position and phase compensation, exact EM wavefronts are restored. For verification, several conformal metasurfaces were designed and numerically studied on metallic cylinders at the microwave spectrum. A proof-of-concept device is fabricated and is experimentally characterized. The results demonstrate the availability of the desirable dual-beam superscatterer with strong backscattering enhancement toward two directions, thus indicating that the distortions induced by an arbitrary platform can be efficiently corrected. Our method affords an efficient alternative for designing high-performance multifunctional optoelectronic devices equipped on a moderately curved platform. Safe detection of an arbitrarily shaped platform is critical for survivability, rescue, or navigation safety in a remote region. Metasurfaces afford great potential due to their strong electromagnetic (EM) wave control. However, studies have mainly focused on the physics and design of metasurfaces on planar plates, which does not satisfy the current requirements of aerodynamics and aesthetics. Herein, we propose a sophisticated strategy to design a metasurface that can wrap over arbitrarily shaped objects with moderate curvature on which optical aberrations are commonly introduced. By designing each meta-atom on the basis of the required position and phase compensation, exact EM wavefronts are restored. For verification, several conformal metasurfaces were designed and numerically studied on metallic cylinders at the microwave spectrum. A proof-of-concept device is fabricated and is experimentally characterized. The results demonstrate the availability of the desirable dual-beam superscatterer with strong backscattering enhancement toward two directions, thus indicating that the distortions induced by an arbitrary platform can be efficiently corrected. Our method affords an efficient alternative for designing high-performance multifunctional optoelectronic devices equipped on a moderately curved platform.
Photonics Research
- Publication Date: Jul. 09, 2018
- Vol. 6, Issue 8, 08000782 (2018)
Label-free sensing of ultralow-weight molecules with all-dielectric metasurfaces supporting bound states in the continuum
Silvia Romano, Gianluigi Zito, Stefania Torino, Giuseppe Calafiore, Erika Penzo, Giuseppe Coppola, Stefano Cabrini, Ivo Rendina, and Vito Mocella
The realization of an efficient optical sensor based on a photonic crystal metasurface supporting bound states in the continuum is reported. Liquids with different refractive indices, ranging from 1.4000 to 1.4480, are infiltrated in a microfluidic chamber bonded to the sensing dielectric metasurface. A bulk liquid sensitivity of 178 nm/RIU is achieved, while a Q-factor of about 2000 gives a sensor figure of merit up to 445 in air at both visible and infrared excitations. Furthermore, the detection of ultralow-molecular-weight (186 Da) molecules is demonstrated with a record resonance shift of 6 nm per less than a 1 nm thick single molecular layer. The system exploits a normal-to-the-surface optical launching scheme, with excellent interrogation stability and demonstrates alignment-free performances, overcoming the limits of standard photonic crystals and plasmonic resonant configurations. The realization of an efficient optical sensor based on a photonic crystal metasurface supporting bound states in the continuum is reported. Liquids with different refractive indices, ranging from 1.4000 to 1.4480, are infiltrated in a microfluidic chamber bonded to the sensing dielectric metasurface. A bulk liquid sensitivity of 178 nm/RIU is achieved, while a Q-factor of about 2000 gives a sensor figure of merit up to 445 in air at both visible and infrared excitations. Furthermore, the detection of ultralow-molecular-weight (186 Da) molecules is demonstrated with a record resonance shift of 6 nm per less than a 1 nm thick single molecular layer. The system exploits a normal-to-the-surface optical launching scheme, with excellent interrogation stability and demonstrates alignment-free performances, overcoming the limits of standard photonic crystals and plasmonic resonant configurations.
Photonics Research
- Publication Date: Jun. 21, 2018
- Vol. 6, Issue 7, 07000726 (2018)
High-efficiency all-dielectric transmission metasurface for linearly polarized light in the visible region
Liu Yang, Dong Wu, Yumin Liu, Chang Liu, Zenghui Xu, Hui Li, Zhongyuan Yu, Li Yu, and Han Ye
We propose and numerically investigate an efficient transmission-mode metasurface that consists of quasi-continuous trapezoid-shaped crystalline silicon nanoantennas on a quartz substrate. This metasurface provides a linear phase gradient and realizes both full 2π phase shift and high transmission efficiency in the operating wavelength range from 740 to 780 nm. At the central wavelength around 751 nm, the total transmission efficiency is up to 88.0% and the section of the desired anomalous refraction is 80.4%. The anomalous refraction angle is 29.62°, and larger refraction angle can be achieved by changing the period of the super cell. We demonstrate a refraction angle as large as 38.59°, and the anomalous transmission efficiency reaches 76.6% at wavelength of 741 nm. It is worth mentioning that the structure is much simpler than conventional metasurfaces based on arrays of discrete nanoantennas. Our research may pave the way for designing efficient all-dielectric phase-gradient metasurfaces and applying them in integrated optical devices for wavefront control. We propose and numerically investigate an efficient transmission-mode metasurface that consists of quasi-continuous trapezoid-shaped crystalline silicon nanoantennas on a quartz substrate. This metasurface provides a linear phase gradient and realizes both full 2π phase shift and high transmission efficiency in the operating wavelength range from 740 to 780 nm. At the central wavelength around 751 nm, the total transmission efficiency is up to 88.0% and the section of the desired anomalous refraction is 80.4%. The anomalous refraction angle is 29.62°, and larger refraction angle can be achieved by changing the period of the super cell. We demonstrate a refraction angle as large as 38.59°, and the anomalous transmission efficiency reaches 76.6% at wavelength of 741 nm. It is worth mentioning that the structure is much simpler than conventional metasurfaces based on arrays of discrete nanoantennas. Our research may pave the way for designing efficient all-dielectric phase-gradient metasurfaces and applying them in integrated optical devices for wavefront control.
Photonics Research
- Publication Date: Apr. 26, 2018
- Vol. 6, Issue 6, 06000517 (2018)
Tailoring active color rendering and multiband photodetection in a vanadium-dioxide-based metamaterial absorber
Shichao Song, Xiaoliang Ma, Mingbo Pu, Xiong Li, Yinghui Guo, Ping Gao, and Xiangang Luo
Metamaterials have demonstrated exotic electromagnetic properties, which offer a good platform for realizing light absorption, photodetection, filtering, and so on. However, broadband multifunctional metamaterial absorbers are restricted in cascaded structures. Here, broadband multifunctional properties were realized by introducing vanadium dioxide into a metamaterial absorber. Through the modified design and highly efficient utilization of multiple resonant modes, both plasmonic tunable color filters and near-infrared photodetectors can be simultaneously achieved by this construction. Meanwhile, active color and a photodetection band in the near-infrared range can become tunable with the insulating–metallic transition of vanadium dioxide. Thus, the variations of rendering colors could correspondingly indicate shifts of the near-infrared photodetection bands. This method theoretically confirms the feasibility of designing multifunctional devices via a vanadium-dioxide-based metamaterial absorber, which holds great promise for future versatile utilization of multiple physical mechanisms to achieve numerous functionalities in a simple nanostructure or device. Metamaterials have demonstrated exotic electromagnetic properties, which offer a good platform for realizing light absorption, photodetection, filtering, and so on. However, broadband multifunctional metamaterial absorbers are restricted in cascaded structures. Here, broadband multifunctional properties were realized by introducing vanadium dioxide into a metamaterial absorber. Through the modified design and highly efficient utilization of multiple resonant modes, both plasmonic tunable color filters and near-infrared photodetectors can be simultaneously achieved by this construction. Meanwhile, active color and a photodetection band in the near-infrared range can become tunable with the insulating–metallic transition of vanadium dioxide. Thus, the variations of rendering colors could correspondingly indicate shifts of the near-infrared photodetection bands. This method theoretically confirms the feasibility of designing multifunctional devices via a vanadium-dioxide-based metamaterial absorber, which holds great promise for future versatile utilization of multiple physical mechanisms to achieve numerous functionalities in a simple nanostructure or device.
Photonics Research
- Publication Date: Apr. 26, 2018
- Vol. 6, Issue 6, 06000492 (2018)
Tuning the metal filling fraction in metal-insulator-metal ultra-broadband perfect absorbers to maximize the absorption bandwidth
Amir Ghobadi, Hodjat Hajian, Alireza Rahimi Rashed, Bayram Butun, and Ekmel Ozbay
In this paper, we propose a methodology to maximize the absorption bandwidth of a metal-insulator-metal (MIM) based absorber. The proposed structure is made of a Cr-Al2O3-Cr multilayer design. At the initial step, the optimum MIM planar design is fabricated and optically characterized. The results show absorption above 0.9 from 400 nm to 850 nm. Afterward, the transfer matrix method is used to find the optimal condition for the perfect light absorption in an ultra-broadband frequency range. This modeling approach predicts that changing the filling fraction of the top Cr layer can extend light absorption toward longer wavelengths. We experimentally proved that the use of proper top Cr thickness and annealing temperature leads to a nearly perfect light absorption from 400 nm to 1150 nm, which is much broader than that of a planar design. Therefore, while keeping the overall process lithography-free, the absorption functionality of the design can be significantly improved. The results presented here can serve as a beacon for future performance-enhanced multilayer designs where a simple fabrication step can boost the overall device response without changing its overall thickness and fabrication simplicity. In this paper, we propose a methodology to maximize the absorption bandwidth of a metal-insulator-metal (MIM) based absorber. The proposed structure is made of a Cr-Al2O3-Cr multilayer design. At the initial step, the optimum MIM planar design is fabricated and optically characterized. The results show absorption above 0.9 from 400 nm to 850 nm. Afterward, the transfer matrix method is used to find the optimal condition for the perfect light absorption in an ultra-broadband frequency range. This modeling approach predicts that changing the filling fraction of the top Cr layer can extend light absorption toward longer wavelengths. We experimentally proved that the use of proper top Cr thickness and annealing temperature leads to a nearly perfect light absorption from 400 nm to 1150 nm, which is much broader than that of a planar design. Therefore, while keeping the overall process lithography-free, the absorption functionality of the design can be significantly improved. The results presented here can serve as a beacon for future performance-enhanced multilayer designs where a simple fabrication step can boost the overall device response without changing its overall thickness and fabrication simplicity.
Photonics Research
- Publication Date: Feb. 12, 2018
- Vol. 6, Issue 3, 03000168 (2018)
Polarization-independent all-silicon dielectric metasurfaces in the terahertz regime
Huifang Zhang, Xueqian Zhang, Quan Xu, Qiu Wang, Yuehong Xu, Minggui Wei, Yanfeng Li, Jianqiang Gu, Zhen Tian, Chunmei Ouyang, Xixiang Zhang, Cong Hu, Jiaguang Han, and Weili Zhang
Dielectric metasurfaces have achieved great success in realizing high-efficiency wavefront control in the optical and infrared ranges. Here, we experimentally demonstrate several efficient, polarization-independent, all-silicon dielectric metasurfaces in the terahertz regime. The metasurfaces are composed of cylindrical silicon pillars on a silicon substrate, which can be easily fabricated using etching technology for semiconductors. By locally tailoring the diameter of the pillars, full control over abrupt phase changes can be achieved. To show the controlling ability of the metasurfaces, an anomalous deflector, three Bessel beam generators, and three vortex beam generators are fabricated and characterized. We also show that the proposed metasurfaces can be easily combined to form composite devices with extended functionalities. The proposed controlling method has promising applications in developing low-loss, ultra-compact spatial terahertz modulation devices. Dielectric metasurfaces have achieved great success in realizing high-efficiency wavefront control in the optical and infrared ranges. Here, we experimentally demonstrate several efficient, polarization-independent, all-silicon dielectric metasurfaces in the terahertz regime. The metasurfaces are composed of cylindrical silicon pillars on a silicon substrate, which can be easily fabricated using etching technology for semiconductors. By locally tailoring the diameter of the pillars, full control over abrupt phase changes can be achieved. To show the controlling ability of the metasurfaces, an anomalous deflector, three Bessel beam generators, and three vortex beam generators are fabricated and characterized. We also show that the proposed metasurfaces can be easily combined to form composite devices with extended functionalities. The proposed controlling method has promising applications in developing low-loss, ultra-compact spatial terahertz modulation devices.
Photonics Research
- Publication Date: Dec. 12, 2017
- Vol. 6, Issue 1, 01000024 (2018)
Tunable spin splitting of Laguerre–Gaussian beams in graphene metamaterials
Wenguo Zhu, Mengjiang Jiang, Heyuan Guan, Jianhui Yu, Huihui Lu, Jun Zhang, and Zhe Chen
Optical spin splitting has attracted significant attention owing to its potential applications in quantum information and precision metrology. However, it is typically small and cannot be controlled efficiently. Here, we enhance the spin splitting by transmitting higher-order Laguerre–Gaussian (LG) beams through graphene metamaterial slabs. The interaction between LG beams and metamaterial results in an orbital-angular-momentum- (OAM) dependent spin splitting. The upper bound of the OAM-dependent spin splitting is found, which varies with the incident OAM and beam waist. Moreover, the spin splitting can be flexibly tuned by modulating the Fermi energy of the graphene sheets. This tunable spin splitting has potential applications in the development of spin-based applications and the manipulation of mid-infrared waves. Optical spin splitting has attracted significant attention owing to its potential applications in quantum information and precision metrology. However, it is typically small and cannot be controlled efficiently. Here, we enhance the spin splitting by transmitting higher-order Laguerre–Gaussian (LG) beams through graphene metamaterial slabs. The interaction between LG beams and metamaterial results in an orbital-angular-momentum- (OAM) dependent spin splitting. The upper bound of the OAM-dependent spin splitting is found, which varies with the incident OAM and beam waist. Moreover, the spin splitting can be flexibly tuned by modulating the Fermi energy of the graphene sheets. This tunable spin splitting has potential applications in the development of spin-based applications and the manipulation of mid-infrared waves.
Photonics Research
- Publication Date: Oct. 07, 2017
- Vol. 5, Issue 6, 06000684 (2017)
Ultrasensitive terahertz metamaterial sensor based on vertical split ring resonators
Wei Wang, Fengping Yan, Siyu Tan, Hong Zhou, and Yafei Hou
An ultrasensitive metamaterial sensor based on double-slot vertical split ring resonators (DVSRRs) is designed and numerically calculated in the terahertz frequency. This DVSRR design produces a fundament LC resonance with a quality factor of about 20 when the incidence magnetic field component normal to the DVSRR array. The resonant characteristics and sensing performance of the DVSRR array design are systematically analyzed employing a contrast method among three similar vertical split ring resonator (SRRs) structures. The research results show that the elimination of bianisotropy, induced by the structural symmetry of the DVSRR design, helps to achieve LC resonance of a high quality factor. Lifting the SRRs up from the substrate sharply reduces the dielectric loss introduced by the substrate. All these factors jointly result in superior sensitivity of the DVSRR to the attributes of analytes. The maximum refractive index sensitivity is 788 GHz/RIU or 1.04×105 nm/RIU. Also, the DVSRR sensor maintains its superior sensing performance for fabrication tolerance ranging from ?4% to 4% and wide range incidence angles up to 50° under both TE and TM illuminations. An ultrasensitive metamaterial sensor based on double-slot vertical split ring resonators (DVSRRs) is designed and numerically calculated in the terahertz frequency. This DVSRR design produces a fundament LC resonance with a quality factor of about 20 when the incidence magnetic field component normal to the DVSRR array. The resonant characteristics and sensing performance of the DVSRR array design are systematically analyzed employing a contrast method among three similar vertical split ring resonator (SRRs) structures. The research results show that the elimination of bianisotropy, induced by the structural symmetry of the DVSRR design, helps to achieve LC resonance of a high quality factor. Lifting the SRRs up from the substrate sharply reduces the dielectric loss introduced by the substrate. All these factors jointly result in superior sensitivity of the DVSRR to the attributes of analytes. The maximum refractive index sensitivity is 788 GHz/RIU or 1.04×105 nm/RIU. Also, the DVSRR sensor maintains its superior sensing performance for fabrication tolerance ranging from ?4% to 4% and wide range incidence angles up to 50° under both TE and TM illuminations.
Photonics Research
- Publication Date: Sep. 15, 2017
- Vol. 5, Issue 6, 06000571 (2017)
Complex band structures of 1D anisotropic graphene photonic crystal
Limei Qi, and Chang Liu
The complex band structures of a 1D anisotropic graphene photonic crystal are investigated, and the dispersion relations are confirmed using the transfer matrix method and simulation of commercial software. It is found that the result of using effective medium theory can fit the derived dispersion curves in the low wave vector. Transmission, absorption, and reflection at oblique incident angles are studied for the structure, respectively. Omni-gaps exist for angles as high as 80° for two polarizations. Physical mechanisms of the tunable dispersion and transmission are explained by the permittivity of graphene and the effective permittivity of the multilayer structure. The complex band structures of a 1D anisotropic graphene photonic crystal are investigated, and the dispersion relations are confirmed using the transfer matrix method and simulation of commercial software. It is found that the result of using effective medium theory can fit the derived dispersion curves in the low wave vector. Transmission, absorption, and reflection at oblique incident angles are studied for the structure, respectively. Omni-gaps exist for angles as high as 80° for two polarizations. Physical mechanisms of the tunable dispersion and transmission are explained by the permittivity of graphene and the effective permittivity of the multilayer structure.
Photonics Research
- Publication Date: Sep. 05, 2017
- Vol. 5, Issue 6, 06000543 (2017)
Tunable and multichannel terahertz perfect absorber due to Tamm surface plasmons with graphene
Xi Wang, Xing Jiang, Qi You, Jun Guo, Xiaoyu Dai, and Yuanjiang Xiang
In this paper, we have shown that perfect absorption at terahertz frequencies can be achieved by using a composite structure where graphene is coated on one-dimensional photonic crystal (1DPC) separated by a dielectric. Due to the excitation of optical Tamm states (OTSs) at the interface between the graphene and 1DPC, a strong absorption phenomenon occurs induced by the coupling of the incident light and OTSs. Although the perfect absorption produced by a metal–distributed Bragg reflector structure has been researched extensively, it is generally at a fixed frequency and not tunable. Here, we show that the perfect absorption at terahertz frequency not only can be tuned to different frequencies but also exhibits a high absorption over a wide angle range. In addition, the absorption of the proposed structure is insensitive to the polarization, and multichannel absorption can be realized by controlling the thickness of the top layer. In this paper, we have shown that perfect absorption at terahertz frequencies can be achieved by using a composite structure where graphene is coated on one-dimensional photonic crystal (1DPC) separated by a dielectric. Due to the excitation of optical Tamm states (OTSs) at the interface between the graphene and 1DPC, a strong absorption phenomenon occurs induced by the coupling of the incident light and OTSs. Although the perfect absorption produced by a metal–distributed Bragg reflector structure has been researched extensively, it is generally at a fixed frequency and not tunable. Here, we show that the perfect absorption at terahertz frequency not only can be tuned to different frequencies but also exhibits a high absorption over a wide angle range. In addition, the absorption of the proposed structure is insensitive to the polarization, and multichannel absorption can be realized by controlling the thickness of the top layer.
Photonics Research
- Publication Date: Sep. 11, 2017
- Vol. 5, Issue 6, 06000536 (2017)
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