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Scalable fabrication of geometry-tunable self-aligned superlattice photonic crystals for spectrum-programmable light trapping
摘要： Superlattice photonic crystals (SPhCs) possess considerable potentials as building blocks for constructing high-performance devices because of their great flexibilities in optical manipulation. From the prospective of practical applications, scalable fabrication of SPhCs with large-area uniformity and precise geometrical controllability has been considered as one prerequisite but still remains a challenge. In this work, we developed an anodic aluminum oxide template-guided approach to realize Ni SPhCs with the maximum area (~500 mm2) ever reported. By virtue of the dual-pore self-alignment effect arising from the periodic anodization electric fields, uniform structures over large areas were obtained for Ni SPhCs. Meanwhile, the geometrical parameters for every array of nanopores in terms of pore depth, size, and morphology can be independently controlled due to the sequential pore-opening. Based on the experimental observation about the geometrical dependence of the light absorption for Ni dual-pore SPhCs, we further fabricated Ni SPhCs with simultaneously-shaped nanopores and nanoconcaves, which not only simplified the fabrication process but also achieved omnidirectional stably-strong (~95%) light absorption spectra. Optical simulations elucidated that surface plasmon resonance and cavity resonance are responsible for the strong light trapping. Notably, the fabrication technique is applicable to Ni SPhCs with different periodicities, leading to spectrally programmable light absorption spectra. With Ni SPhCs as solar absorber, the water evaporation efficiency of a solar steam generation system and the open circuit voltage of a solar thermoelectric generator demonstrated 2.3 and 2.5 times improvement, respectively.
关键词： geometrically tunable,surface plasmon resonance,self alignment,superlattice photonic crystal,cavity resonance,anodic aluminum oxide template
更新于2025-09-19 17:15:36
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Enhanced nonlinear optical properties of ZnS nanoparticles in 1D polymer photonic crystal cavity
摘要： The enhanced nonlinear optical absorption and optical limiting properties of polymeric one dimensional photonic crystal (1DPhC) with ZnS nanoparticles as defect are reported. The 1DPhC was fabricated by spin coating technique, using polystyrene (PS) and cellulose acetate (CA) as high and low refractive index materials. ZnS nanoparticles were synthesized in CA solution by laser ablation technique and the structural, morphological and non linear optical characterizations were done. A microcavity structure with cavity resonance around 532 nm was designed by inserting ZnS NPs/CA defect layer between two Bragg reflectors comprising 10 bilayers of CA/PS. A significant enhancement (4.6 times) in both nonlinear absorption and optical limiting properties of 1DPhC with ZnS defect layer was observed under 532 nm pulse excitation compared to the ZnS reference sample. The enhancement in the observed nonlinear optical properties of the system could be accredited to the confinement of optical field due to the localization of photons in the cavity mode. The current system can play crucial roles in designing practical nonlinear optical devices, such as optical limiters, optical switchers etc.
关键词： 1D Photonic crystal,Nonlinear absorption,Optical limiting,Z-scan
更新于2025-09-19 17:15:36
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Acoustic wave transparency in nitrogen-vacancy centers in a photonic crystal
摘要： We show that the interaction of nitrogen-vacancy centers in diamond with a strain field in a photonic crystal can lead to acoustic wave transparency. This occurs due to the strong interaction of photons with the modified photonic reservoir near the photonic band edge created by the photonic crystal. For achieving this, we explore the properties of the spin states of the ground state of the nitrogen-vacancy centers, where one transition interacts with a strain field while the other transition has spontaneous emission that occurs near the edge of the photonic band gap, which should be in the microwave regime. We show that depending on the form of the photonic density of states acoustic wave transparency is obtained at one or two frequencies.
关键词： Induced transparency,Photonic crystal,Non-Markovian dynamics,Acoustic field,Nitrogen-vacancy center in diamond
更新于2025-09-19 17:15:36
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Design of terahertz photoconductive antenna arrays based on defective photonic crystal substrates
摘要： In this paper, arrays of two different terahertz (THz) antennas based on defective photonic crystal (DPC) substrates are proposed and their radiation characteristics are investigated by using full-wave simulation. We show that employing DPC substrates in THz photoconductive antenna (PCA) arrays reduces the amount of power coupled to the substrate surface waves and, as a result, decreases the mutual coupling between the elements of the antenna array and increases the directivity in the boresight direction. By studying 1 × 2 arrays of bowtie and four-leaf-clover-shaped antennas, we show that either the improvement of directivity in a broad bandwidth or the enhancement of photomixer antenna impedance at a resonant frequency can be considered in the design of the DPC substrate. Therefore, the proposed approach can significantly improve the efficiency and radiation performance of THz photomixer antennas resulting in an improved effective THz radiated power in the desirable direction. The proposed DPC substrate can be considered as a way to realize sub-millimeter-sized dielectric resonator antennas at terahertz frequencies. In addition, this cost-effective technique can reduce the necessity of exploiting hyper-hemispherical Si lenses by overcoming the adverse effects of the thick substrate which is of prime importance in PCA arrays from a practical viewpoint.
关键词： Arrays,Defective photonic crystal substrate,Propagation waves,Terahertz antennas
更新于2025-09-19 17:15:36
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All-Fiber CO2 Sensor Using Hollow Core PCF Operating in the 2 μm Region
摘要： A realistic implementation of an all-fiber CO2 sensor, using 74 cm of hollow core photonic crystal fiber (HC-PCF) as the cavity for light/gas interaction, has been implemented. It is based on CO2 absorbance in the 2 μm region. The working range is from 2% to 100% CO2 concentration at 1 atm total pressure and the response time obtained was 10 min. Depending on the concentration level, the sensor operates at one of three different wavelengths (2003.5 nm, 1997.0 nm and 1954.5 nm) to maintain a high sensitivity across all the working range.
关键词： gas,sensor,tunable laser,carbon dioxide monitoring,fiber bragg grating,photonic crystal fiber
更新于2025-09-19 17:15:36
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Optical Properties of Planar and Annular Ternary Superconducting Photonic Crystals in Near-Zero-Permittivity Operation Range
摘要： Optical properties of ternary superconducting planar/annular photonic crystals composed of a high-temperature superconductor and two dielectrics were theoretically investigated based on transfer matrix methods in Cartesian and cylindrical coordinates. Electrodynamics of superconductor were modelled using two-fluid model. It is of interest to observe that, for a planar structure, there exists an additional high reflectance band termed as superpolariton gap near the superconducting threshold wavelength for the TM wave at oblique incidences and some reflection dips also were found in the TM reflectance. However, the superpolariton gap and reflection dips were seen for an annular geometry at higher order azimuthal number. For an annular structure, the size of superpolariton gap can be controlled by simply adjusting the starting radius. Moreover, the superpolariton gap in both structures strongly depends on the operating temperature, different combinations of dielectric refractive indices, and thicknesses of dielectric materials.
关键词： Annular,Superconductor,Photonic crystal,Superpolariton
更新于2025-09-19 17:15:36
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Broadband Dispersion Compensation of Single Mode Fiber by using Modified Decagonal Photonic Crystal Fiber having High Birefringence
摘要： This paper presents a highly birefringent dispersion compensating microstructure modified decagonal photonic crystal fiber for broadband transmission communication system. According to simulation, negative dispersion coefficient of ?610 ps/(nm.km) and a relative dispersion slope (RDS) close to that of single mode fiber of about 0.0036 nm-1 with birefringence of the order 2.1×10-2 was obtained at 1550 nm. The variation of structural parameters is also studied to evaluate the tolerance of the fabrication. Moreover, effective area, residual dispersion, effective dispersion, confinement loss, and nonlinear coefficient of the proposed modified decagonal photonic crystal fiber (M-DPCF) are also mentioned and discussed.
关键词： Photonic crystal fiber,Birefringence,Dispersion compensating fiber,Effective mode area,Residual dispersion,Full-vector Finite Element Method
更新于2025-09-19 17:15:36
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Highly sensitive and temperature-compensated fiber bending sensing based on directional resonance coupling in photonic crystal fibers
摘要： A highly sensitive bending sensor with temperature-compensation based on magnetic fluids (MF) infiltrated photonic crystal fiber (PCF) is presented. Specific cladding air-holes are filled with MF material to form defective channels and introduce new degrees of freedom for fiber sensing. The structure designed in such way can achieve simultaneous measurement of bend-curvature and bend-direction with temperature compensation. The bending sensitivity can reach to ?6.544 nm/m?1 with a high linearity within the range of curvature from ?10 m?1 to 10 m?1. The proposed two-dimensional (2D) bending vector sensor cannot only improve the sensing precision and measurement range, but also reduce the metrical difficulty and simplify the process.
关键词： Photonic crystal fiber,Directional resonance coupling,Bending sensor
更新于2025-09-19 17:15:36
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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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All-optical InAsP/InP nanowire switches integrated in a Si photonic crystal
摘要： We report the successful demonstration of all-optical switching using a sub-wavelength InP/InAsP nanowire integrated in a silicon photonic crystal at telecommunication wavelengths. In this work, we employed two different hybrid nanowire cavities based on an air-trench in photonic crystals. These hybrid cavities have the advantages of both material functionality of III-V material and the low propagation loss of the silicon waveguide. The nanowire induced line-defect photonic crystal cavity shows a Q-factor of 25000, higher than the hybrid systems we previously demonstrated. The switching time is 150 ps, which is among the fastest nanowire switches reported. We found that the switching time was clearly dependent on the Q-factor. From measurements performed while changing pump power, we have estimated the switching energy to be a few hundred femtojoules. This value is lower than that of a reference silicon photonic crystal cavity without a nanowire and an air trench under the same pumping condition. This indicates that the InP/InAsP nanowire integrated in a silicon photonic crystal has potential to contribute to reducing the switching energy.
关键词： all-optical switch,AFM manipulation,nanophotonics,photonic crystal,nanowire,photonic integrated circuits
更新于2025-09-19 17:13:59