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Magnetoelectric uniaxial metamaterials as wide-angle polarization-insensitive matching layers
摘要： Antire?ection or impedance matching is a topic that has been extensively researched by the optical and microwave communities over the past century and until today. However, due to the diverging wave impedances of TE (s) and TM (p) polarizations with increasing incident angle, it is impossible to achieve perfect matching simultaneously for both polarizations at varying incidence angles with a single conventional isotropic matching layer. To achieve polarization-insensitive matching at an arbitrary incident angle, we propose a magnetoelectric uniaxial metamaterial layer (MEUML) that is inspired by the perfectly matched layer (PML) concept in computational electromagnetics. Similar to the PML, the MEUML requires speci?c uniaxial permittivity and permeability tensors. However, to simultaneously control both the transversal and longitudinal material parameters is not an easy task. To date, a true PML has not been realized with metamaterials. In this paper, we employ a simple and yet special metamaterial unit cell to achieve such control and synthesize a physical MEUML. The unit cell comprises two parallel metallic rings separated by a holey substrate. The transversal electric and magnetic dipole moments, and the longitudinal capacitive and diamagnetic coupling between the rings are judiciously controlled to achieve the required permittivity and permeability tensors. To aid the MEUML synthesis, we also introduce a technique that can extract the material parameter tensors at any incident angle. We ?rst demonstrate this concept by achieving polarization-insensitive matching of a high-index substrate at 45? with a single subwavelength-thick MEUML. We further adapt the concept to the microwave regime by developing a MEUML-based radome. Exceptional matching performance was obtained both in the simulations and measurements. The re?ectance remains below 5% from normal incidence (0?) to near grazing angle (85?) for both polarizations and over a wide bandwidth. With this unprecedented control of the material parameter tensors, the MEUML concept not only can be applied to impedance matching, but also can be utilized in many exotic applications that require extreme control of the material properties.
关键词： wide-angle,impedance matching,polarization-insensitive,radome,magnetoelectric uniaxial metamaterials
更新于2025-09-23 15:21:21
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Multilayer Non-interacting Dielectric Metasurfaces For Multiwavelength Metaoptics
摘要： Metasurfaces provide a versatile platform for manipulating the wavefront of light using planar nanostructured surfaces. Transmissive metasurfaces, with full 2π phase control, are a particularly attractive platform for replacing conventional optical elements due to their small footprint and broad functionality. However, the operational bandwidth of metasurfaces has been a critical limitation and is directly connected to either their resonant response or the diffractive dispersion of their lattice. While multiwavelength and continuous band operation have been demonstrated, the elements suffer from either low efficiency, reduced imaging quality, or limited element size. Here, we propose a platform that provides for multiwavelength operation by employing tightly spaced multilayer dielectric metasurfaces. As a proof of concept, we demonstrate a multiwavelength metalens doublet (NA=0.42) with focusing efficiencies of 38% and 52% at wavelengths of 1180 nm and 1680 nm, respectively. We further show how this approach can be extended to three wavelength metalenses as well as a spectral splitter. This approach could find applications in fluorescent microscopy, digital imaging, and color routing.
关键词： Multiwavelength metalens,spectrum splitter,metasurface doublet,polarization-insensitive
更新于2025-09-23 15:21:01
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Broadband polarization-insensitive amplitude and phase modulators based on graphene-covered buried and ridge silicon waveguides
摘要： In this paper, four easy-to-fabricate graphene-based Si waveguide modulators are presented to overcome the strong polarization dependency of graphene-based modulators. The modulation features of two newly proposed structures, i.e. two graphene-based buried silicon waveguides in addition to two standard ridge silicon waveguides at the telecommunication wavelength of are studied. The results show that for certain widths of each waveguide (the height is constant), the amplitude and phase modulations clearly become polarization-insensitive. The amplitude modulation depths for both the TE and TM modes are equal for these optimized waveguides with the precision of . Moreover, in the proposed modulators, the maximum variations of the real parts of the effective mode indices (EMI) for both the TE and TM modes coincide with each other with an excellent precision ( . This precision value is much smaller than the standard criterion value for confirming a polarization-insensitive phase modulation. For proposed structures, the average modulation depth (MD) and maximum variation of the real parts of EMI are about and respectively. Thus, it means to clearly imply small footprints for both amplitude and phase modulations. Furthermore, the performances of all the structures are studied for all optical telecommunication wavelengths. Even without making any changes to the structures designed at at appropriate wavelength intervals, the structures exhibit polarization-insensitive behaviors.
关键词： Graphene,Polarization-insensitive,Optical modulator,Buried waveguide,Ridge waveguide
更新于2025-09-23 15:21:01
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Graphene Plasmonic Fractal Metamaterials for Broadband Photodetectors
摘要： Metamaterials have recently established a new paradigm for enhanced light absorption in state-of-the-art photodetectors. Here, we demonstrate broadband, highly efficient, polarization-insensitive, and gate-tunable photodetection at room temperature in a novel metadevice based on gold/graphene Sierpinski carpet plasmonic fractals. We observed an unprecedented internal quantum efficiency up to 100% from the near-infrared to the visible range with an upper bound of optical detectivity of 1011 Jones and a gain up to 106, which is a fingerprint of multiple hot carriers photogenerated in graphene. Also, we show a 100-fold enhanced photodetection due to highly focused (up to a record factor of |e/e0| ≈ 20 for graphene) electromagnetic fields induced by electrically tunable multimodal plasmons, spatially localized in self-similar fashion on the metasurface. Our findings give direct insight into the physical processes governing graphene plasmonic fractal metamaterials. the proposed structure represents a promising route for the realization of a broadband, compact, and active platform for future optoelectronic devices including multiband bio/chemical and light sensors.
关键词： graphene,metamaterials,plasmonic fractals,gate-tunable,photodetectors,polarization-insensitive,broadband
更新于2025-09-23 15:19:57
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[IEEE 2018 18th Mediterranean Microwave Symposium (MMS) - Istanbul, Turkey (2018.10.31-2018.11.2)] 2018 18th Mediterranean Microwave Symposium (MMS) - Polarization Insensitive Metamaterial Absorber Using Sunflower Shaped Unit Cell
摘要： In this paper, a novel polarization insensitive metamaterial absorber using sunflower shaped unit cell is proposed. The performance of the proposed absorber was demonstrated with 3D full-wave EM solver under normal incidence for TE and TM polarization modes. Due to the symmetric geometry of the sunflower shaped unit cell, the proposed absorber provides a high level of absorptivity, about %90, for both TE and TM modes at 11.9 GHz. To enhance the absorptivity, we then created a hollow at the center of the proposed unit cell. The later device resonates at 11.7 GHz, and provides perfect absorption for both polarization modes. Our study reveals that employing hollow type symmetrical gaps provokes the interaction of EM wave and the metamaterial, and can lead to the perfect metamaterials for X-band absorber applications.
关键词： Metamaterial,absorber,X band,unit cell,polarization insensitive
更新于2025-09-19 17:15:36
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Polarization-insensitive fiber-to-fiber gain of semiconductor optical amplifier using closely stacked InAs/GaAs quantum dots
摘要： The gain characteristics of a semiconductor optical amplifier (SOA) that contains forty layers of closely stacked InAs/GaAs quantum dots (QDs) were studied by employing a fiber-to-fiber measurement system. The fiber-to-fiber gain values obtained for transverse-electric (TE)- and transverse-magnetic (TM)-polarized optical input signals exhibited their maxima at a wavelength of 1100 nm, which corresponds to the excited state of the closely stacked QDs. In the wavelength range from 1060 to 1170 nm, the gain obtained for TE-polarized input signal was slightly higher than that for TM-polarized input signal and the absolute gain difference was less than 1 dB for an injection current of 80 mA. The small but non-zero difference of the gain reflects the polarization anisotropy of the optical gain provided by the closely stacked QDs. Our results suggest that closely stacked QDs are suitable for realizing polarization-insensitive SOA device with operation bandwidths of more than 100 nm.
关键词： fiber-to-fiber gain,quantum dots,polarization-insensitive,semiconductor optical amplifier
更新于2025-09-19 17:13:59
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Polarization-insensitive Waveguide Crossings Based on SWGs-assisted MMI
摘要： A polarization-insensitive waveguide crossing based on sub-wavelength gratings (SWGs) assisted multimode interference (MMI) is proposed and demonstrated on silicon-on-insulator (SOI) platform. The proposed device is characterized with low insertion loss and low crosstalk for both TE and TM polarizations from 1500 nm to 1600 nm, 0.69 dB (0.61 dB) for TE (TM) at 1550 nm. The device can be fabricated with single etch process to achieve a footprint of 12.5×12.5 μm2. Further analysis shows that the device has a fabrication tolerance of ±30 nm for the MMI structure. The proposed device can be employed in photonic integrated circuits with polarization-division-(de)multiplexing functionality.
关键词： Waveguide crossing,Polarization-insensitive,Subwavelength grating,MMI
更新于2025-09-16 10:30:52
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - A novel polarization-insensitive optical filter on silicon
摘要： A silicon-based polarization-insensitive optical filter is designed and demonstrated by using dual multimode-waveguide-gratings. For the ~300μm-long device, the 3dB-bandwidth is ~11nm and the excess loss is ~1.5dB for both polarizations.
关键词： bandwidth,polarization-insensitive,optical filter
更新于2025-09-16 10:30:52
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A Bilayer Plasmonic Metasurface for Polarizationa??Insensitive Bidirectional Perfect Absorption
摘要： The implementation of perfect absorption of optical waves in artificial nanostructures has attracted tremendous attention among the scientific community. Traditional approaches based on metamaterials can only absorb optical waves in one direction while reflecting optical waves in the other direction. Here, a polarization-insensitive bidirectional perfect absorber that is composed of bilayer gold nano disks embedded into a silicon nitride substrate is demonstrated. The bidirectional perfect absorption in the proposed bilayer metasurface, which is irrelevant to the coherent of optical waves, is attributed to the multiple reflections and interference of optical waves in the bilayer structures. The proposed perfect absorber shall boost its applications in optical anti-counterfeiting, integrated photodetectors, and solar thermal applications.
关键词： alignment-free,few-layer metasurfaces,polarization-insensitive,bidirectional perfect absorption
更新于2025-09-16 10:30:52
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Nano-plasmonic Bundt Optenna for broadband polarization-insensitive and enhanced infrared detection
摘要： Infrared detection devices are becoming miniature with micro or nano-scale size. The advantages of downsizing come on the expense of insufficient collection of infrared radiation. Therefore, utilizing nano-plasmonic optical antennas becomes mandatory. However, it is desirable to develop antennas with broad bandwidth, polarization insensitivity, wide field-of-view, and reasonable plasmonic losses in order to collect most of incident infrared radiation and enhance power absorption efficiency. Here, an innovative optical antenna (optenna) is proposed and demonstrated for the first time. It has a novel shape of Bundt baking-pan. The gold Bundt is arranged in a periodic array that can be placed on top of a thin-film infrared absorbing layer. The developed optenna can squeeze infrared electric and magnetic fields to 50 nm-wide area in order to enhance material absorption efficiency. It demonstrates polarization insensitivity and ultra-broad bandwidth with a large fractional-bandwidth within the near, shortwave, and midwave infrared bands. It shows a remarkable enhanced power absorption efficiency up to 8 orders of magnitude with a reasonable average power loss of ?3 dB and 80° field-of-view. It can be promising for future applications in solar-cells, telecommunication photodetectors, shortwave cameras, and midwave microbolometers.
关键词： optical antenna,infrared detection,polarization-insensitive,broadband,nano-plasmonic
更新于2025-09-11 14:15:04