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- 摘要
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- 实验方案
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Tailoring the plasmonic Fano resonance in metallic photonic crystals
摘要： Periodically arranged metallic nanowires on top of a waveguide layer show a strong coupling between the particle plasmon of the wires and the waveguide mode. By introducing a dielectric spacer layer between the metallic structures and the waveguide layer, this coupling can be reduced. Here, the thickness of this spacer layer is varied and the coupling strength is determined for each spacer layer thickness by fitting an effective energy matrix to the energy positions of the resonance peaks. It is found that the coupling strength can be very well described by the electric field amplitude of the waveguide mode at the location of the nanowires. We carried out experiments and found very good agreement with theory and our simple model. Using this method, we achieved experimentally an extremely small mode splitting as small as 25 meV leading to very sharp spectral features. Our pathway and design for tailoring the coupling strength of plasmonic Fano resonances will enable the design of highly sensitive plasmonic sensor devices and open the door for narrow plasmonic spectral features for nonlinear optics and slow light propagation.
关键词： photonic crystals,coupling strength,Fano resonance,plasmonic,waveguide
更新于2025-09-23 15:19:57
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Opal-Like Photonic Structuring of Perovskite Solar Cells Using a Genetic Algorithm Approach
摘要： Light management is an important area of photovoltaic research, but little is known about it in perovskite solar cells. The present work numerically studies the positive effect of structuring the photo-active layer of perovskite material. This structuration consists of a hybrid absorbing layer made of an uniform part and an opal-like part. A genetic algorithm approach allows us to determine the optimal combination among more than 1.4 × 109 potential combinations. The optimal combination provides an internal quantum efficiency of 98.1%, nearly 2% higher than for an equivalent unstructured photo-active layer. The robustness of the optimum against potential experimental deviations, as well as the angular dependency of the proposed structure, are examined in the present study.
关键词： photonic crystals,perovskite,photovoltaics,light management
更新于2025-09-23 15:19:57
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Wideband absorption in one dimensional bilayer-graphene embedded photonic multilayer structure
摘要： In this article, we propose a one-dimensional graphene-based multilayer structure which composed of traditional dielectric material and graphene. The dependence of absorption characteristics of this structure on the chemical potential of graphene, the optical thickness of the dielectric layer, the loss of the dielectric material and the incident angle are investigated by using the transfer matrix method. It is shown that the absorption bandwidth of the structure can be modulated by the chemical potential of graphene and the absorption is insensitive to the refractive index and geometric thickness of the dielectric material within a certain range. It is also shown that the absorption is generally insensitive to the angle of incidence. These findings have potential applications for designing tunable broadband absorbers and related optoelectronic devices.
关键词： absorption characteristics,wideband absorption,photonic crystals,graphene,transfer matrix method
更新于2025-09-23 15:19:57
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Inkless Multi-Color Writing and Copying of Laser-Programmable Photonic Crystals
摘要： Rewritable papers, as an environmentally friendly alternative for information delivery, hold great promise to reduce the abundant uses of ordinary papers that cause severe environmental problems. In recent decades, photonic crystals (PCs) have shown great potential in developing rewritable papers. However, existing PC papers still confront many challenges, including poor storage stability, short-cycle lifetime, monotonous colors, and absence of copying capability. Herein, we report the fabrication of a rewritable PC paper based on programmable configurations of a synthesized shape memory polymer (SMP). The resulting SMP-based PC paper does not need additional inks and can be facilely written by near infrared (NIR) light with assistance from a pre-printed black paper as a photothermal layer. Heating from the black paper induces various stable configurations of the PCs, thus creating multiple colors in the irradiated areas. Moreover, the PC paper possesses excellent colorful copying capability that can transform information from a paper with pre-printed black letters or complex images via scanning with NIR light. These images can be stably stored for more than 6 months at ambient conditions, which can be even erased and rewritten over 50 times without significant loss in color quality. This environment-friendly SMP-based PC paper with extraordinary properties holds great promise in the fields of next-generation office papers, smart price tags, and anti-counterfeiting labels.
关键词： NIR light,copying capability,multi-color writing,rewritable papers,photonic crystals,shape memory polymer
更新于2025-09-23 15:19:57
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[IEEE 2019 International Conference on Smart Systems and Inventive Technology (ICSSIT) - Tirunelveli, India (2019.11.27-2019.11.29)] 2019 International Conference on Smart Systems and Inventive Technology (ICSSIT) - Power Quality Enhancement of a Photovoltaic Based Micro Grid System Using Optimized Fuzzy Controller with SAPF
摘要： We investigate terahertz quantum cascade lasers with a dense array of active micropillars forming the gain medium. Depending on the size of these pillars relative to the emission wavelength different optical regimes are identified. For pillar dimensions on the order of the emission wavelength, a photonic crystal resonator is created. Single mode emission is observed at high symmetry points of the photonic band structure. The selection mechanism of the favored laser mode is studied by analyzing the gain enhancement effect for eigenmodes with a low group velocity and a large mode confinement of the electric field energy in the micropillars. Subwavelength micropillar arrays constitute a photonic metamaterial, which can be described using an effective medium approximation. Similar to a bulk laser ridge, the array forms a Fabry–Pérot resonator that is defined by the boundaries of the array. From the longitudinal mode spacing, we derive an effective group index of the pillar medium. Limitations in terms of minimum filling factors and waveguide losses for the realization of subwavelength micropillar and nanowire array terahertz quantum cascade lasers are investigated.
关键词： optical metamaterials,terahertz,optical waveguides,Photonic crystals,quantum cascade lasers
更新于2025-09-23 15:19:57
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[IEEE 2018 20th International Conference on Transparent Optical Networks (ICTON) - Bucharest (2018.7.1-2018.7.5)] 2018 20th International Conference on Transparent Optical Networks (ICTON) - All Dielectric Mode Order Transformation Photonic Structure Design by Evolutionary Optimization Approach
摘要： In this manuscript, an evolutionary algorithm is applied to design a mode order converter photonic crystal structure for achieving transformation of the propagating fundamental mode to the higher order mode. In order to transform incident light mode from an even mode to an odd mode, predefined mask object functions are employed. The cross-sectional field profiles at the output face of the optimized structure are utilized to evaluate the optimization cost function to achieve mode order transformation task. In the study, the optimized structure composed of dielectric alumina (Al2O3) rods and time domain analyses of the optimization process are done by using finite-difference time domain method. Furthermore, numerical results are confirmed by experiments for designed structure at the microwave frequencies. It is shown that the numerical calculations and experimental measurements agree well with each other.
关键词： mode order converter,differential evolution algorithm,phase shift,photonic crystals,integrated optics
更新于2025-09-23 15:19:57
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[IEEE 2018 IEEE Research and Applications of Photonics In Defense Conference (RAPID) - Miramar Beach, FL (2018.8.22-2018.8.24)] 2018 IEEE Research and Applications of Photonics In Defense Conference (RAPID) - Implementing Photonic Crystals, Instead of Metamaterials, in the Media of Transformation Optics-based Devices
摘要： Extending Transformation Optics in optical range is challenging because of losses in metamaterials. We propose, instead, to use dielectric photonic crystals capable of supporting superluminal wave propagation and realizing spatial dispersion of refractive index values. Implementing these materials in cylindrical invisibility cloaks is demonstrated.
关键词： spatial dispersion of indices,superluminal wave propagation,anisotropic photonic crystals
更新于2025-09-23 15:19:57
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Rise and side infiltration in opals and porous materials for their skin-free replica synthesis
摘要： A floating opal placed on a certain liquid will cause the liquid to climb through the opal gaps, fill all its pores, and stop almost of its upper surface without covering it. A drop of solution with a surface tension much lower than that of water, deposited on a hydrophilic substrate near an opal, rapidly spread over a large surface forming a film which will surround the opal and infiltrate it from the side without covering it. High quality, skin-free, inverse opals can be synthesized by rise and side infiltration of solution in opals. The overlayer absence leads to the fabrication of mechanically robust, crack-free, completely filled photonic crystals which preserve the long rage order of initial opals. Inverse opals of sodium silicate were synthesized starting from polystyrene nanospheres self-assembled through hanging drop technique followed by their rise and side infiltration, casting, and template removal. Crystalline material inverse opals such as glycine, sodium chloride, and sulfur were also synthesized.
关键词： skin-free,photonic crystals,inverse opals,rise infiltration,porous materials
更新于2025-09-23 15:19:57
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High contrast ratio all-optical 4?×?2 encoder based on two-dimensional photonic crystals
摘要： Optical encoders are circuits that are used in the design of optical processors. To reduce the size of optical devices, it is necessary to design small-scale logic circuits. In this study an all-optical 4 × 2 encoder based on 2D photonic crystals, was designed and simulated. The simple structure of this optical encoder makes it possible to build it in optical integrated circuits. Owing to its low dimensional structure and the use of simple defect paths, the delay time of the encoder will be reduced and so, the data bit rate will be increased. The obtained transmission delay time for the proposed encoder is less than 0.1 ps. Another characteristic of the proposed optical encoder is that the output optical power in “0” logic state is very low, which increases the contrast ratio as compared to the previous works. The contrast ratio CR = 16.5 dB was obtained for the proposed encoder.
关键词： Optical encoder,Photonic crystals,Contrast ratio
更新于2025-09-19 17:15:36
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[IEEE 2019 21st International Conference on Transparent Optical Networks (ICTON) - Angers, France (2019.7.9-2019.7.13)] 2019 21st International Conference on Transparent Optical Networks (ICTON) - Spin Plasmonics and Surface Enhanced Raman Spectroscopy in Label Free Biomolecular Sensing
摘要： We report the results of a study of an optical sensor based on a channel-drop technique with two cascaded cavities in photonic-crystal slabs. Quality factors and intensities of the resonant modes of the sensor were analyzed with three-dimensional simulations. With the introduction of a re?ector in the bus-channel and by control of the coupling between the two cavities and the drop-channel, the drop ef?ciency can be remarkably increased. In addition to the simulation, the two cavity sensor is fabricated and tested for optical response to water and oil in?ltration. Both direct visual imaging and quantitative analysis were applied in experiment. A difference of refractive index Δn = 0.12 between water and oil samples results in a wavelength shift of 18.3 nm, which greatly matches the simulation result of 20 nm and indicates a sensitivity of 153 nm RIU?1. Both resonant peaks for water and oil in?ltration have good selectivity in their transmission spectrum. The contrast between the broadband output of the bus-channel and the highly wavelength-selective outputs of the drop-channel opens opportunities for the two cascaded-cavity system as a fundamental building block for a multiplex drop-channel array for all-optical sensing, which can be widely used for bio/chemical detection and environmental monitoring.
关键词： photonic integrated circuits,multiplexing,optical sensors,photonic crystals,optical coupling,Cavity resonators,optical waveguide,optical devices
更新于2025-09-19 17:13:59