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A Wideband Terahertz Transmissive Polarization Manipulator Based on Metasurfaces
摘要： Wideband and multifunction operation for THz polarization manipulating devices has been desired for a wide range of applications. In this paper, a novel wideband transmissive type polarization manipulator based on metasurfaces is proposed in the THz region. The designed metasurface acts as a multifunctional polarization manipulator, performing linear to circular polarization conversion (LCPC) for relative bandwidth 43.9% (0.94 THz to 1.47 THz) for incident x/y polarizations and a wideband bandpass filter with relative bandwidth 67% (0.713 THz to 1.4346 THz) for incident slant (xy) polarizations. Wideband LCPC operation is achieved using a unique diagonal symmetric structure based on a bilayered metasurface. In order to confirm the validation of proposed results, electromagnetic simulation was carried out in two industry-standard software packages, HFSS and CST, using frequency domain and time domain solvers, respectively. Close agreement between numerical results depicts the validity and reliability of the proposed design. Polarized wave trajectory, equivalent microscopic circuit, physical mechanisms, and impact of different geometrical parameters on the performance is investigated. To the best of our knowledge, this is the first polarization manipulator based on bilayered metasurfaces. The same structure can be used as for LCPC and the transmit reject filter for THz wireless communication, including THz satellite communications, the future of communication. Moreover, they can be used in THz imaging and biomolecular control devices.
关键词： polarization manipulation,receive filter,linear to circular polarization conversion,terahertz
更新于2025-09-16 10:30:52
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[IEEE 2019 Thirteenth International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Rome, Italy (2019.9.16-2019.9.21)] 2019 Thirteenth International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Wide Band Polarization Converter Graphene Metasurface for Mid-Infrared Band
摘要： Wide band, insensitive incidence angle graphene metasurface for polarization conversion is introduced in this work. A high Polarization Conversion Ratio (PCR) is verified in Mid-Infrared band by using a graphene as an upper conductor for metasurface. The metasurface construction is composed of a single layer of graphene, which has a half ring slots with rectangular slot connecting between them while the whole shape is rotated with 45o. Silicon dioxide substrate is used with a metal backed ground. The simulation results of the proposed metasurface indicate that a linearly polarized incident wave is converted to a circular polarized one over more than one THz along the Mid-Infrared frequency band. PCR has a maximum value of approximately 98% at 1.45 THz. The polarization conversion ratio is studied for different angles of incidence, with stable value for a wide range of incident angles.
关键词： Insensitive incidence angle,Graphene metasurface,Wide band,Mid-Infrared band,Polarization Conversion Ratio (PCR)
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Fabrication of Tuned Lipss-Based Metallic Polarization Gratings
摘要： Surface nanostructuring has received increasing attention in recent years due to the wide range of applications in which it offers advantages. Particularly, Laser-Induced Periodic Surface Structures (LIPSS) have proven useful for surface functionalization [1]. LIPSS are periodic formations generated in most materials when irradiated with linearly polarized radiation. The orientation of these structures is directly linked to the polarization of the incident light, while other parameters of their morphology such as period and depth can be controlled with the number of pulses, fluence, wavelength and pulse duration of the incident light. Due to their periodic nature, LIPSS behave optically as nanogratings [2], which have been largely studied as polarization converters (or Polarization Gratings, PGs). PGs are structures that introduce a phase shift in the incident light, which produces a change in its polarization state [3]. Therefore, PGs have potential applications as reflective waveplates [4], showing advantages over transmission waveplates such as higher damage thresholds and a lower temporal dispersion of the pulse. So far, PGs have been fabricated with methods such as direct laser interference or lithography [5]. The main drawbacks of these methods include limited choice of periods for the generated structures or a complex and environmentally unfriendly fabrication process, which could be overcome by a fabrication method based on LIPSS. In order to fabricate LIPSS-based PGs, stainless steel samples were irradiated with a 800 nm femtosecond Ti:Sapphire laser. The laser was focused onto the surface of the sample through a cylindrical lens with a focal length of 10 cm. The sample was translated perpendicular to the laser beam with a mechanical stage at a constant speed, generating LIPSS in a large area of 5 mm x 5 mm in a few seconds. By varying the fluence of the beam and the speed of the stage, LIPSS with different parameters were fabricated. Topography of the samples were characterized with AFM and SEM (Fig. 1a) microscopes, and polarization conversion and reflectivity were examined with a polarimeter. Results show that a gradual change in LIPSS morphology is associated to a gradual change in the ellipticity of the laser beam (Fig. 1b). It is also observed that LIPSS geometry changes smoothly with processing parameters. Therefore, it is proven that LIPSS-based PGs can be fabricated experimentally, and that the properties of such PGs can be tuned changing the LIPSS geometry, as expected. These results are in good agreement with the performed FDTD simulations for different LIPSS morphologies.
关键词： Surface nanostructuring,Polarization Gratings,LIPSS,Polarization conversion,Femtosecond laser
更新于2025-09-12 10:27:22
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Trichromatic and Tri-polarization-channel Holography with Non-interleaved Dielectric Metasurface
摘要： Metasurfaces hold great potentials for advanced holographic display with extraordinary information capacity and pixel sizes in an ultrathin flat profile. Dual-polarization channel to encode two independent phase profiles or spatially multiplexed meta-holography by interleaved metasurfaces are captivated popular solutions to projecting multiplexed and vectorial images. However, the intrinsic limit of orthogonal polarization-channels, their crosstalk due to coupling between meta-atoms, and interleaving-induced degradation of efficiency and reconstructed image quality set great barriers for sophisticated meta-holography from being widely adopted. Here we report a non-interleaved TiO2 metasurface holography, and three distinct phase profiles are encoded into three orthogonal polarization bases with almost zero crosstalk. The corresponding three independently constructed intensity profiles are therefore assigned to trichromatic (RGB) beams, resulting in high-quality and high-efficiency vectorial meta-holography in the whole visible regime. Our strategy presents an unconventionally advanced holographic scheme by synergizing trichromatic colors and tri-polarization channels, simply realized with a minimalist non-interleaved metasurface. Our work unlocks the metasurface’s potentials on massive information storage, polarization optics, polarimetric imaging, holographic data encryption, etc.
关键词： polarization conversion,non-interleaved metasurface,tri-polarization-channel metasurface,trichromatic vectorial holography,dielectric nanostructures
更新于2025-09-12 10:27:22
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Temperature Dependence of InGaN / GaN Multiple Quantum Well Solar Cells
摘要： Elements based on nitride family and more specifically, those of the GaN/InGaN family, present a great interest for renewable energy conversion systems as they offer huge potentialities in photovoltaic applications, as example for the realization of concentration solar cells. This interest is linked to the possibility to enlarge the part of the solar energetic spectrum that a solar cell is able to capture thanks to the possibilities of growing multilayers cells with various band-gap and thus, with various absorption bands. In this paper, the performance of InGaN/GaN multiple quantum well MQW solar cells with respect to the N-polar orientation. is investigated .In order to obtain the exact conversion efficiency, the temperature effect as well as the spontaneous and piezoelectric polarization effect are taking into consideration in model. The results reveal that the increase of temperature decreases significantly the MQW solar cell efficiency. Our results and discussion would be helpful in designing and fabricating high efficiency InGaN/GaN solar cell in experiment.
关键词： InGaN/GaN solar cells,Polarization,Conversion efficiency,Photovoltaic effect,Temperature
更新于2025-09-12 10:27:22
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Dual-band asymmetric optical transmission of both linearly and circularly polarized waves using bilayer coupled complementary chiral metasurface
摘要： It is highly desirable to develop asymmetric transmission (AT) devices for both linearly and circularly polarized light. However, currently existing metamaterial-based AT devices require multi-step micro-nano fabrication processes and usually realize AT responses only for linearly or circularly polarized waves, not simultaneously for both. We here propose a dual-band AT device for both linearly and circularly polarized waves in the near-infrared region by using a bilayer coupled complementary chiral metasurface, which includes a half-gammadion-shape gold (Au) structural layer and its Babinet’s complimentary copy. Unlike other multilayer AT devices working at optical frequencies, it takes less micro-nano fabrication steps. Besides, with the help of chirality and the inherent near-?eld coupling e?ect between the two complementary Au layers, the maximal AT parameters for linearly and circularly polarized waves can reach up to 0.45 and 0.56, respectively. The underlying mechanisms of dual-band AT responses are also investigated in depth from the perspectives of chirality and coupling e?ect. Our work o?ers a new and simple approach to high-performance AT devices, helps to better understand near-?led coupling e?ect in coupled complementary metasurfaces, and also expands their application ?elds.
关键词： chiral metasurface,asymmetric transmission,polarization conversion,coupling effect,near-infrared
更新于2025-09-11 14:15:04
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Broadband Linear-to-Circular Polarization Conversion Enabled by Birefringent Off-Resonance Reflective Metasurfaces
摘要： Due to the scarcity of circular polarization light sources, linear-to-circular polarization conversion is required to generate circularly polarized light for a variety of applications. Despite significant past efforts, broadband linear-to-circular polarization conversion remains elusive particularly in the terahertz and midinfrared frequency ranges. Here we propose a novel mechanism based on coupled mode theory, and experimentally demonstrate at terahertz frequencies that highly efficient (power conversion efficiency approaching unity) and ultrabroadband (fractional bandwidth up to 80%) linear-to-circular polarization conversion can be accomplished by the judicious design of birefringent metasurfaces. The underlying mechanism operates in the frequency range between well separated resonances, and relies upon the phase response of these resonances away from the resonant frequencies, as well as the balance of the resonant and nonresonant channels. This mechanism is applicable for any operating frequencies from microwave to visible. The present Letter potentially opens a wide range of opportunities in wireless communications, spectroscopy, and emergent quantum materials research where circularly polarized light is desired.
关键词： linear-to-circular polarization conversion,midinfrared,birefringent metasurfaces,terahertz,broadband
更新于2025-09-11 14:15:04
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Design of broadband polarization converter for terahertz waves
摘要： A broadband reflective polarization converter is proposed. The unit cell of polarization converter is composed of a single-split resonant ring, a double-split resonant ring, a dielectric substrate and a metallic ground. The simulated results show that the polarization converter can convert x-polarized waves into y-polarized waves and obtain a broadband polarization conversion from 0.501 0 THz to 1.390 0 THz with the polarization conversion ratio (PCR) beyond 80% at normal incidence. Moreover, the surface current distributions are investigated to explain the polarization conversion mechanism. Finally, a good agreement is achieved between simulated and measured results. The polarization converter can be applied in terahertz imaging, communication and stealthy technology.
关键词： metasurface,terahertz waves,polarization conversion ratio,broadband,polarization converter
更新于2025-09-10 09:29:36
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[IEEE 2018 IEEE International Conference on Computational Electromagnetics (ICCEM) - Chengdu, China (2018.3.26-2018.3.28)] 2018 IEEE International Conference on Computational Electromagnetics (ICCEM) - Single Layer Multi-Polarization Transmitarray in C-Band with Beam-Steering Capability
摘要： A single layer multi-polarization transmitarray is presented in this paper, whose structure can be much simpler than the traditional multi-layer frequency selective surface transmitarray. The proposed transmitarray consists of numerous split ring elements and has three working conditions. It is designed, simulated and measured in C-band. The measurement result shows that the transmitarray can switch polarization of the incident wave and set separation beam direction at the same time
关键词： beam separation,phase modulation,transmitarray,polarization conversion
更新于2025-09-10 09:29:36
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[IEEE 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz2018) - Nagoya, Japan (2018.9.9-2018.9.14)] 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Linear to Circular Polarization Conversion of Terahertz Wave Using Metallic Helix Array
摘要： We developed a 2D array of 3D metallic helix which converts linearly polarized terahertz (THz) wave into circularly polarized THz wave and acts as a broadband THz wave polarizer. It covers the frequency range from 140 GHz to 250 GHz, close to one octave. We made two different arrays which consist of left-handed and right-handed metallic helices and we confirmed that these arrays change the linearly polarized THz wave into right-hand and left-hand circularly polarized THz wave respectively.
关键词： terahertz wave,metallic helix array,broadband polarizer,polarization conversion
更新于2025-09-10 09:29:36