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- 摘要
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- 实验方案
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Decorative near-infrared transmission filters featuring high-efficiency and angular-insensitivity employing 1D photonic crystals
摘要： We present a new scheme for visibly-opaque but near-infrared-transmitting filters involving 7 layers based on one-dimensional ternary photonic crystals, with capabilities in reaching nearly 100% transmission efficiency in the near-infrared region. Different decorative reflection colors can be created by adding additional three layers while maintaining the near-infrared transmission performance. In addition, our proposed structural colors show great angular insensitivity up to ±60° for both transverse electric and transverse magnetic polarizations, which are highly desired in various fields. The facile strategy described here involves a simple deposition method for the fabrication, thereby having great potential in diverse applications such as image sensors, anti-counterfeit tag, and optical measurement systems.
关键词： colored decorations,multilayer structures,photonic crystals,near-infrared (NIR)-transmitting filters
更新于2025-09-09 09:28:46
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Peculiarities of band structure of one-dimensional photonic crystals
摘要： In this paper, the peculiarities of the band structure of one-dimensional photonic crystals are studied, when the periodic (quasiperiodic) medium is inhomogeneous in relation to both the dielectric and magnetic properties. It is shown that the photonic band gap does not appear at small angles of incidence, in the case when the modulation depths of the dielectric permittivity and magnetic permeability coincide. The possibilities of obtaining photonic bandgaps in the terahertz radiation region are considered. The features of the band structure of photonic crystal with different spatial periods of the dielectric permittivity and magnetic permeability are investigated. It is shown that in this case, four PBGs appear in each diffraction reflection order.
关键词： Dielectric permittivity,Band structure,Magnetic permeability,Photonic crystals,Terahertz radiation
更新于2025-09-09 09:28:46
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Engineering Modes of PT Symmetric Photonic Crystals
摘要： This work explores the effects of parity-time (PT) symmetry on the modes of photonic crystal defect waveguides. Two designs are considered. In the ?rst, the defect modes are protected from PT transitions, but edge modes in the complex conjugate frequency regime appear. In the second design, the defect modes exhibit thresholdless PT transitions.
关键词： photonic crystals,optical waveguides,parity-time symmetry,photonic integrated circuits,semiconductor waveguides
更新于2025-09-04 15:30:14
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DESIGNING PLANE WAVE MODULATORS USING 1DPC NANOSTRUCTURE WITH R-GRIN DEFECT LAYER
摘要： In this paper, we introduce plane wave modulators that are designed using one-dimensional photonic crystals (1DPC) containing radial gradient refractive index (r-GRIN) defect layers. Three kinds of r-GRIN materials with di?erent refractive index distribution functions are applied in numerical analysis. The properties of the phase and intensity of the transmitted plane wave beam through proposed structures are studied using the transfer matrix method. Radially-dependent defect modes, modulated phase and intensity are obtained according to the refractive index distribution functions. The results are predictable by regarding the Bragg condition and destructive interference, which are the origins of the photonic band gap (PBG). Due to the radial-dependency of the defect layer’s refractive index, the rays passing through di?erent transverse positions experience di?erent optical pathways. Therefore, the defect modes and transmitted spectrum (phase and amplitude) vary transversely. This study demonstrates another ability of the arti?cial PC structures to design plane wave modulators and manipulate its phase and intensity.
关键词： radial gradient refractive index,transfer matrix method,one-dimensional photonic crystals,plane wave modulators,photonic band gap
更新于2025-09-04 15:30:14
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IMPROVEMENT OF RADIATION CHARACTERISTICS OF BALANCED ANTIPODAL VIVALDI ANTENNA USING TRASFORMATION OPTICS
摘要： Transformation optics is a convenient method to control paths of electromagnetic waves and radiation characteristics of antennas. In this paper, we try to increase the gain of Balanced Antipodal Vivaldi Antenna (BAVA) over 8{16 GHz frequency band using an optical conformal transformation. The proposed antenna can be implemented by ordinary dielectric materials and graded photonic crystals (GPCs). In this designed BAVA, better side-lobe level (SLL) and cross-polarization are achieved compared to a conventional BAVA. Simulation results validate the performance of the design approach.
关键词： graded photonic crystals,Transformation optics,Balanced Antipodal Vivaldi Antenna,cross-polarization,side-lobe level,gain improvement
更新于2025-09-04 15:30:14
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Topological one-way fiber of second Chern number
摘要： One-way waveguides have been discovered as topological edge states in two-dimensional (2D) photonic crystals. Here, we design one-way fiber modes in a 3D magnetic Weyl photonic crystal realizable at microwave frequencies. We first obtain a 3D Chern crystal with a non-zero first Chern number by annihilating the Weyl points through supercell modulation. When the modulation becomes helixes, one-way modes develop along the winding axis, with the number of modes determined by the spatial frequency of the helix. These single-polarization single-mode and multi-mode one-way fibers, having nearly identical group and phase velocities, are topologically-protected by the second Chern number in the 4D parameter space of the 3D wavevectors plus the winding angle of the helix. This work suggests a unique way to utilize high-dimensional topological physics using topological defects.
关键词： topological defects,Chern number,Weyl photonic crystals,one-way waveguides,topological photonics
更新于2025-09-04 15:30:14
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Redshift gaps in one-dimensional photonic crystals containing hyperbolic metamaterials
摘要： In conventional all-dielectric one-dimensional photonic crystals (1DPCs), photonic gaps will shift toward short wavelengths (blueshift) as the incident angle increases for both transverse magnetic (TM) and transverse electric (TE) polarizations. We theoretically and experimentally achieve redshift gaps in 1DPCs composed of alternative hyperbolic metamaterials (HMMs) and dielectrics for TM polarization based on the anomalous wavevector dispersion of HMMs. The HMM is mimicked by layered titanium dioxide and silver with a subwavelength unit cell. However, the gaps remain to be blue-shifted for TE polarization. Therefore, the edges of such gaps can be utilized for high-e?ciency wide-angle polarization selection. We achieve e?cient polarization selection for incident angles ranging from 50 o to 80o at the wavelength of 365 nm.
关键词： one-dimensional photonic crystals,redshift gaps,polarization selection,hyperbolic metamaterials
更新于2025-09-04 15:30:14
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Time-modulated Periodic Systems with PT Symmetry
摘要： This work explores the effects of parity-time (PT) symmetry in time-modulated periodic systems. Mechanisms for dynamic tunability of exceptional points are presented. We show that synthetic linear momentum imparted by time-modulation leads to uni-directional exceptional points. Such structures could see application in uni-directional lasers with tunable directionality.
关键词： semiconductor lasers,photonic crystals,distributed feedback lasers,time-varying circuits,parity-time symmetry,time-varying systems,optical modulation
更新于2025-09-04 15:30:14
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Lasing in optimized two-dimensional iron-nail-shaped rod photonic crystals
摘要： We demonstrated lasing at the Γ-point band-edge (BE) modes in optimized two-dimensional iron-nail-shaped rod photonic crystals by optical pulse pumping at room temperature. As the radius of the rod increased quadratically toward the edge of the pattern, the quality factor of the Γ-point BE mode increased up to three times, and the modal volume decreased to 56% compared with the values of the original Γ-point BE mode because of the reduction of the optical loss in the horizontal direction. Single-mode lasing from an optimized iron-nail-shaped rod array with an InGaAsP multiple quantum well embedded in the nail heads was observed at a low threshold pump power of 160 μW. Real-image-based numerical simulations showed that the lasing actions originated from the optimized Γ-point BE mode and agreed well with the measurement results, including the lasing polarization, wavelength, and near-field image.
关键词： optical pulse pumping,photonic crystals,iron-nail-shaped rod,lasing,band-edge modes
更新于2025-09-04 15:30:14
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DESIGN OF A PYRAMIDAL HORN ANTENNA WITH LOW E-PLANE SIDELOBES USING TRANSFORMATION OPTICS
摘要： Transformation optics is a convenient way to control the pattern of electromagnetic ?elds. In this paper, using a novel transformation, we propose the design procedure of a horn antenna having low backlobe and sidelobe levels in its E-plane. By applying conformal transformation, the rectangular horn proposed in this paper can be realized with isotropic materials. This proposed antenna can be easily implemented by both ordinary dielectric materials and isotropic graded refractive index (GRIN) materials. In the ?rst proposed design, in addition to the isotropy, homogeneity is furthermore introduced into the horn, and only four kinds of isotropic materials are required throughout. In the second design, it is demonstrated that the designed structure can also be implemented by graded photonic crystals (GPCs) operating in metamaterial regime. They have low loss as well as broad frequency band and are easy to implement. Simulation results are presented to validate the design approach.
关键词： low sidelobes,horn antenna,graded refractive index,graded photonic crystals,Transformation optics,isotropic materials,conformal transformation
更新于2025-09-04 15:30:14