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Dependence on hydrostatic pressure in two-dimensional triangular photonic crystals
摘要： The plane wave expansion method is used to calculate photonic band structures for transverse electric (TE) polarization, in a two-dimensional (2D) photonic crystal with a hexagonal lattice composed air holes with triangular cross sections embedded in a semiconductor (GaAs) background. This study focuses on the dependence of the GaAs dielectric constant on pressure and temperature. The air holes are isosceles triangles with fixed areas. We found that the width of the photonic band gap increases, when the internal angle of the triangle and the angle of rotation in the unit cell are increased at constant hydrostatic pressure values. The width of the photonic band gap remains unchanged when the hydrostatic pressure is increased at fixed internal and rotation angle values. In addition, when considering an H1 defect in the crystal, using the supercell technique, we find that the number of defective modes within the photonic band gap increases with the triangle rotation in the unit cell.
关键词： plane wave expansion method,hydrostatic pressure,defect mode,Photonic crystal,semiconductor
更新于2025-09-23 15:22:29
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Superconducting one-dimensional photonic crystal with coupled semiconductor defects
摘要： We investigate the impact of the insertion of a semiconductor defect on the transmittance spectrum of a one-dimensional photonic crystal composed by alternating layers of superconducting materials. We report that the effect of the insertion of the semiconductor defect originates a defective mode in the photonic band gap that exhibits a shift towards long-wavelength regimes. Unexpectedly, for high values of temperatures, it is observed that the defective mode reduces its confinement as well as influences the optical response of the photonic crystal rather than the pressure. We also extend our analysis to the case of two coupled defects of GaAs, and it is studied the effect of the relative distance between these two defects. Our numerical results reveal that the defective mode has a significant reduction in its quality factor as well as it displays an asymmetry in the transmittance spectrum when the defects are close to each other.
关键词： Transfer matrix method,Defect mode,Semiconductor,Transmittance spectrum,One-dimensional photonic crystal,Superconductor
更新于2025-09-23 15:21:01
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Comparative study of defect mode intensity and wavelength modulation in Bragg fiber waveguide sensors
摘要： Sensing parameters of Bragg ?ber waveguides having a defect layer in the cladding region are studied theoretically for bio-sensing and thickness monitoring applications. A comparison between Bragg ?ber waveguides consist of a liquid-core surrounded with alternate high refractive index (R.I.) contrast of claddings and low R.I. contrast of claddings is presented. In non-homogeneous multilayer cylindrical system, the transmittance of proposed waveguide-based sensors is formulated using transfer matrix method and Hankel formalism. Both considered structures show photonic bandgap with a narrow passband in the bandgap region. This narrow passband is treated as sensing signal because its position and intensity depends on the diameter and refractive index of core material. The high refractive index contrast cladding waveguide shows larger intensity shift than low refractive index contrast cladding waveguide. The presence of defect layer in both considered waveguides is able to increase the sensing parameters like detection accuracy and overall performance.
关键词： Quality parameter,Liquid core Bragg ?ber waveguide,Defect mode,Detection accuracy,Sensitivity
更新于2025-09-23 15:19:57
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A Thina??Film Flexible Defecta??Mode Laser
摘要： Laser emission from a flexible defect-mode structure consisting of two photopolymerized liquid crystal thin films separated by a dye-doped polymethylmethacrylate defect layer is demonstrated. A simple and cost-effective film transfer technique is used to fabricate the flexible laser and the corresponding laser emission characteristics, which shows single-mode laser emission at λ = 582 nm, with an excitation threshold of Eth = 12.3 ± 0.5 μJ cm?2 per pulse and a slope efficiency of ηs = 6.0 ± 0.3%, are presented. The polarization state of the laser emission are also presented and are compared with the findings reported in the literature. Finally, laser-beam steering is demonstrated up to 42° by subjecting the device to a mechanically induced deformation that creates a radius of curvature of 5 mm, which is of potential interest for conformable and wearable technology platforms.
关键词： thin-film lasers,liquid crystals,flexible lasers,defect-mode lasers
更新于2025-09-23 15:19:57
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Emerging Waveguide Technology || Photonic Crystal Waveguides
摘要： The original results of theoretical and experimental studies and the properties of microwave one-dimensional waveguide photonic crystals have been generalized. Methods for describing the electrodynamic characteristics of photonic crystals and their relationship with the parameters of periodic structures filling the waveguides have been presented. The results of an investigation on the characteristics of microwave waveguide photonic crystals made in the form of dielectric matrices with air inclusions have been presented. The model of effective dielectric permittivity has been proposed for describing the characteristics of the investigated photonic crystals containing layers with a large number of air inclusions. New types of microwave low-dimensional waveguide photonic crystals containing periodically alternating elements that are sources of higher type waves have been described. The possibility of effective control of the amplitude-frequency characteristics of microwave photonic crystals by means of electric and magnetic fields has been analyzed. Examples of new applications of waveguide photonic crystals in the microwave range have been given: the measuring parameters of the materials and semiconductor nanostructures that play the role of the microwave photonic crystals' periodicity defect; the resonators of near-field microwave microscopes; small-sized matched loads for centimeter and millimeter wavelength ranges on the basis of microwave photonic crystals.
关键词： low-dimensional photonic crystal,electrically controlled characteristics,forbidden bands,defect mode,measurement of micro- and nanostructures,microwave matched loads,microwave photonic crystals
更新于2025-09-19 17:13:59
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Analysis of Bragg fiber waveguides having a defect layer for biosensing application
摘要： A novel hollow core Bragg fiber waveguides having a defect layer are proposed and analyzed theoretically for sensing application. Matching the electric and magnetic fields at various interfaces, a relation between fields of first layer with final layer has been stabilized; hence, the equations for reflectance and transmittance of proposed structure are derived. Due to periodicity of concentric cylindrical structure, a perfect photonic band gap is observed in considered wavelength range. The presence of defect layer in cylindrical periodic structure shows a peak corresponding to defect mode in perfect photonic band gap region. The full width at half maxima of this peak depends on the periodicity of the cladding layers. Also, the spectral position and shift of peak of defect mode depend on the angle of incidence of light, refractive index of core material and design wavelength of structure. Therefore, it is more appropriate to consider this peak of defect mode as sensing signal instead of considering whole photonic band gap as sensing signal.
关键词： Bragg fiber waveguide,sensitivity,transfer matrix method,high and low contrast cladding,defect mode
更新于2025-09-11 14:15:04
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Transmission Spectra of a Symmetric Photonic Crystal Structure with a High-Permittivity Interstitial Layer
摘要： Transmission spectra are recorded for a one-dimensional photonic crystal structure with the permittivity of the interstitial (or cavity) layer exceeding the permittivity of layers in Bragg mirrors by many times. It is shown that the transmission can be suppressed almost completely both in the photonic band gap (except for a narrow defect-mode region) and beyond it. Specific features of the energy density distribution of the wave field over the structure are revealed.
关键词： photonic crystal,transmission spectra,defect mode,high-permittivity interstitial layer,energy density distribution
更新于2025-09-10 09:29:36
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Tuning of the defect mode in a 1D superconductor-semiconductor crystal with hydrostatic pressure dependent frequency of the transverse optical phonons
摘要： This study aims to investigate a transmittance spectrum in a one-dimensional photonic crystal, which is surrounded by air and composed of alternating layers of a superconductor (HgBa2Ca2Cu3O8+δ) and a semiconductor (GaAs), using the transfer matrix and two-fluid models. Herein, we considered the pressure-dependence of the superconductor’s critical temperature and the pressure-dependence, in the semiconductor, in both the angular frequency of the transverse optical phonons and the thickness of layers. Initially, we found that increasing the pressure for fixed thickness values of the superconductor results in a shift in the larger frequencies of the transmittance spectrum and the photonic band gaps. With an increase in the thickness of the superconductor layer at a fixed pressure and thickness values of the semiconductor, an increase in the width of the photonic band gaps was observed. When a defective GaAs semiconductor layer was inserted into the structure due to the dissipative features of the semi-conductor, a defective mode with a transmittance of less than 1.0 was found inside the photonic band gaps. When the thickness of the superconductor layer was increased, while keeping the pressure and thickness of the semiconductor constant, the defect mode shifted to shorter frequencies. It was also found that the shift and the number of defective modes in the photonic band gaps increase when the thickness of the defective semiconductor layer increases.
关键词： superconductor,transfer-matrix method,semiconductor,defect mode,Photonic crystal
更新于2025-09-10 09:29:36
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A new method for glucose detection using the one dimensional defective photonic crystals
摘要： In order to enhance the sensing and measuring process of glucose, a sensitive tool surrounding environment. Therefore, we have studied the effects of many physical parameters on the position of the transmitted resonant peak. We have deduced that the glucose properties. Glucose is an important biomaterial can be affected by the should be developed to stimulate glucose properties. In the present paper, we propose intensity is formed within the photonic band gap which is directly related to the insertion of the glucose solution inside the defect layer. A resonant peak with a sharp theoretically the one dimensional photonic crystals that contain a defect layer to act as basics of the characteristic matrix method. Our proposed idea is mainly based on the a sensor for glucose detection. The theoretical modeling is essentially based on the defective photonic crystals.
关键词： Defect mode,Photonic band gaps,Glucose detection,Photonic crystals
更新于2025-09-09 09:28:46
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Unidirectional absorption properties in a defective semiconductor-dielectric asymmetric triadic Cantor photonic crystal
摘要： It is well known that the defective asymmetric bilayer photonic crystal (PC), air/(DB)NA(BD)M/air, where A and B are dielectrics, D is lossy material, and N, M are stack numbers with N≠M, exhibits unidirectional absorption phenomena. In this work we theoretically study whether the defective asymmetric Cantor PC also exhibit the unidirectional optical property. The considered PC is the defective asymmetric Cantor PC, air/TCSN/A/TCSM/air, where TCSN is the N stage triadic Cantor structure composed of B and D; the semiconductor, n-InSb, is chosen as D. Our results show that their absorption spectra also exhibit unidirectional properties. Besides, the absorption peaks has defect mode depending on the defect layers just similar to the defect modes in the transmittance spectra of the usual symmetry photonic crystals.
关键词： photonic crystal,semiconductor,unidirectional absorption,defect mode
更新于2025-09-04 15:30:14