Kind Of Photonic Crystal Research Articles

The Nested Topological Band-Gap Structure for the Periodic Domain Walls in a Photonic Super-Lattice

We study the nested topological band-gap structure of one-dimensional (1D) photonic super-lattices. One cell of the super-lattice is composed of two kinds of photonic crystals (PhCs) with different topologies so that there is a domain wall (DW) state at the interface between the two PhCs. We find that the coupling of periodic DWs could form a new band-gap structure inside the original gap. The new band-gap structure could be topologically nontrivial, and a topological phase transition can occur if the structural or material parameters of the PhCs are tuned. Theoretically, we prove that the Hamiltonian of such coupled DWs can be reduced to the simple Su–Schrieffer–Heeger (SSH) model. Then, if two super-lattices carrying different topological phases are attached, a new topological interface state can occur at the interface between the two super-lattices. Finally, we find the nested topological band-gap structure in two-dimensional (2D) photonic super-lattices. Consequently, such nested topological structures can widely exist in complex super-lattices. Our work improves the topological study of photonic super-lattices and provides a new way to realize topological interface states and topological phase transitions in 1D and 2D photonic super-lattices. Topological interface states in super-lattices are sensitive to frequency and have high accuracy, which is desired for high-performance filters and high-finesse cavities.

Artificial Neural Network for Photonic Crystal Band Structure Prediction in Different Geometric Parameters and Refractive Indexes

In this study, an artificial neural network that can predict the band structure of 2-D photonic crystals is developed. Three kinds of photonic crystals in a square lattice, triangular lattice, and honeycomb lattice and two kinds of materials with different refractive indices are investigated. Using the length of the wave vectors in the reduced Brillouin zone, band number, r/a ratio, and the refractive indices as the dataset, the desired ANN is trained to predict the eigenfrequencies of the photonic modes and depict the photonic band structures with a correlation coefficient greater than 0.99. By increasing the number of neurons in the hidden layer, the correlation coefficient can be further increased over 0.999.

Upconversion fluorescent tuning based on CdS and SiO2 photonic crystals for computer chip label

Manipulating fluorescence color to achieve patterned function may access to many applications and remains some challenges. In this work, we provide an effective way to manipulate upconversion fluorescence through the photonic crystals. The structure of the photonic crystals (PCs) has a regulatory effect on upconversion fluorescence. We assembled NaYF4:Yb3+/Er3+ upconversion nanoparticles (UCNPs) with SiO2 and CdS photonic crystals respectively to obtain the photonic crystals/upconversion nanoparticles (PCs/UCNPs) composites. We studied the manipulating mechanism of two kinds of photonic crystals on upconversion fluorescence, and realized patterning application. This study provides a new way to realize information coding, patterned display of fluorescence manipulating.

Multiangle Patterned Photonic Films Based on CdS and SiO2 Nanoparticles for Bar Code Applications

This paper proposes a patterned material composed of two types of photonic crystals based on CdS and SiO2 nanoparticles. We combined the photonic crystals with poly(ethylene glycol) diacrylate (PEGDA) by nanoparticle self-assembly and UV curing and successfully formed a material containing the different photonic crystals. The material prepared contains two kinds of photonic crystals with different refractive indices, CdS and SiO2 nanoparticles, and due to the large difference in refractive indices of the two materials, the reflection wavelengths of the photonic crystals composed of the two materials also have disparities when the incident angle changes. Macroscopically, the structural colors of the two photonic crystals change with the change in incident angle. In response to this phenomenon, we designed a variety of applications based on a multiangle patterned photonic crystal film to achieve a variety of information storage functions by changing the incident angle and, through the angle change, to achieve lipstick logo, mobile phone bar code, and antipeeping keyboard applications.

A Multi-Parameter Sensor Based on Cascaded Photonic Crystal Cavities Filled with Magnetic Fluid

A kind of photonic crystal (PC) micro-cavity sensor based on magnetic fluid (MF) filling is designed with simulation model. Generally, many sensors’ designs are based on a universal temperature in the whole structure. However, strong photothermal effect in high Q micro-cavities will lead to different temperatures between cavities and environment inevitably. In many theoretical PC sensor designs, researchers neglected the different temperature between environment and cavities. This simple hypothesis will probably lead to failure of sensor design and get wrong temperature. Moreover, few theoretical or experimental works have been done to study optical cavity’s heating process and temperature. We propose that researchers should take seriously about this point. Here, the designed cascaded micro-cavity structure has three spectral lines and a reversible sensitivity matrix, which can simultaneously detect magnetic field, ambient temperature and MF micro-cavity temperature. It can solve the magnetic field and temperature cross-sensitivity problem, and further, distinguish the different temperatures of environment and magnetic fluid cavities. The influence of hole radius and slab thickness on the depth and Q value of the resonant spectral line are also studied. Responses of three dips to magnetic field, ambient temperature and MF micro-cavity temperature are simulated, respectively, where dip 1 belongs to MF cavity 1, dip 2 and dip 3 belong to MF cavity 2. The obtained magnetic field sensitivities are 2.89 pm/Oe, 4.57 pm/Oe, and 5.14 pm/Oe, respectively; the ambient temperature sensitivities are 65.51 pm/K, 50.94 pm/K, and 58.98 pm/K, respectively; and the MF micro-cavity temperature sensitivities are −14.41 pm/K, −17.06 pm/K, and −18.81 pm/K, respectively.

Surface plasmons in metamaterial heterostructures

ABSTRACT The extensive research of layered materials has revealed that it is possible to obtain a new degree of freedom for tuning the dispersion properties. Based on this concept, researchers have investigated the hyperbolic metamaterials. Recently, several kinds of photonic crystals have been proposed as classical counterparts of the layered materials. However, observation of nanostructured metamaterials from the perspective of the metamaterial structural design properties has remained difficult until now. Thus, we consider the propagation of surface plasmon polaritons (SPPs) at the boundary of geometrically different metamaterials. Herein, we consider two-layered and multilayered composites. All the heterostructures under consideration are made of the alternating graphene and dielectric sheets. We analytically estimate dispersion properties, absorption and propagation lengths of SPPs. The variation of graphene dielectric functions is described by the Drude model. On top of all, we analytically identify the key factors influencing propagation length along with the absorption enhancement highly desirable in terahertz photoconductive antennas and consider analytical variations aiming to tune the dispersion relations.

Hydrophobic Poly(tert-butyl acrylate) Photonic Crystals towards Robust Energy-Saving Performance.

Photonic crystals (PCs) have been widely applied in optical, energy, and biological fields owing to their periodic crystal structure. However, the major challenges are easy cracking and poor structural color, seriously hindering their practical applications. Now, hydrophobic poly(tert-butyl acrylate) (P(t-BA)) PCs have been developed with relatively lower glass transition temperature (Tg ), large crack-free area, excellent hydrophobic properties, and brilliant structure color. This method based on hydrophobic groups (tertiary butyl groups) provides a reference for designing new kinds of PCs via the monomers with relatively lower Tg . Moreover, the P(t-BA) PCs film were applied as the photoluminescence (PL) enhanced film to enhance the PL intensity of CdSe@ZnS QDs by 10-fold in a liquid-crystal display (LCD) device. The new-type hydrophobic force assembled PCs may open an innovative avenue toward new-generation energy-saving devices.

Observation of a Topological Edge State in the X‐ray Band

AbstractThe possibility of obtaining edge states of light that are robust against disorder by mimicking the topological properties of a solid‐state system has brought a profound impact on optical sciences. In the short‐wavelength region, X‐ray science and technology is undergoing tremendous development. It requires high‐precision optics with exquisite control of light properties and robustness against structural perturbations. Therefore, it is very attractive to extend the concept of optical topological manipulation to the X‐ray regime. Herein, the topological edge state is theoretically proposed and experimentally demonstrated at the interface of two kinds of photonic crystals having different bandgap topological characteristics in the X‐ray regime. Remarkably, this topologically protected edge state is immune to the thickness disorder as long as the zero‐average‐effective‐mass condition is satisfied. This work extends the topological photonics to the X‐ray regime and paves the way for the development of novel X‐ray optics such as high‐resolution X‐ray filters/monochromators, or X‐ray quantum optics, to realize the phenomena such as Rabi splitting that are robust against disorders.

Numerical Study of 1D Wave Propagation through Double Negative Photonic Crystal

Photonic crystals are having many applications in different fields like wave guides, high efficiency antenna etc. The conventional photonic crystal contains alternating layers of Double Positive media having high and low positive refractive index values. Recently another kind of unconventional photonic crystal is proposed which consists of a Double Negative meta-material and a Double Positive medium. While in conventional photonic crystals the band gaps are formed due to Bragg scattering of fields, in unconventional photonic crystals the band gaps are formed due to both Bragg scattering and volume averaged zero refractive index of the unit cell. Here we propose a new kind of photonic crystal which consists of two Double Negative meta-materials having different refractive indices. The computational study of the propagation of electromagnetic wave through one dimensional Double Negative photonic crystal is reported. One dimensional Finite Difference Time Domain method is used for the study. Drude model is used in this paper to define the dispersion property of Double Negative media.

Development of 3mm three-port Y-junction magnetic optical circulator with two-dimensional magneto-photonic crystals

Two kinds of defect structures of two-dimensional (2D) magnetic-photonic crystal (MPCs) are envisaged to realize circulators in millimeter wave band. The band gaps of the two kinds of photonic crystals are calculated by the plane wave expansion method. The function of the circulator is simulated by finite element method. The calculated excellent external characteristics of the circulator show that MPCs is a promising way for generating an optical circulator.

Dual-mode multicolored photonic crystal patterns enabled by ultraviolet-responsive core-shell colloidal spheres

In this study, we developed a new kind of dual-mode multicolored photonic crystals (PCs), which could be used as a new type of dye, and achieved multicolored patterns. This kind of PCs can exhibit not only distinct structural colors due to Bragg's law of diffraction but also non-structural colors due to fluorescence. We used ultraviolet (UV)-responsive colloidal spheres synthesized by polymerization of semi-continuous emulsions to assemble the PCs. In this synthesis, the fluorescent precursors with carbamate groups were locally restricted to the shell of prepared spheres. UV irradiation can induce photo-decomposition of the carbamate groups in the fluorescent precursors, generating amino groups in the process. This process allowed the assembled PCs to exhibit fluorescence through treatment with fluorescamine. We prepared two-dimensional (2D) multicolored photonic patterns of different sizes, with both reflection and fluorescence modes. These patterns were prepared either by vertical deposition under selective UV irradiation, or by spray coating. In addition, we fabricated three-dimensional (3D) multicolored photonic patterns using 3D templates, as well as through spray coating. The results expand the concept of responsive PCs, and offer potential applications for multicolored photonic crystal patterns (PC patterns) in the field of optical storage, color displays, and anti-counterfeiting.

Design and Preparation of a Functional One-Dimensional Photonic Crystal with Low Emissivity in the Region of 8–14 μm

Low-emissivity materials are widely used in thermal radiation control. They can be made of photonic crystal (PC) characterized by the band gap where the emissivity is low. By introducing a defect (doping), a high emissivity peak can be achieved at a certain wavelength in the band gap to make the PC more composite and multifunctional. In this paper, three commonly-used coating materials, namely, Ge, ZnSe, and Si, are adopted to produce a PC which is poorly emissive in 8–14 μm and highly emissive at 10.6 μm due to a Si doping layer. With such a special spectrum, this kind of PC has the potential of suppressing detection by both far-infrared and CO2 laser radiation. The spectrum of the sample obtained by Fourier transform infrared spectrometer is in satisfactory agreement with the theoretical curve.

TiO2 activity enhancement through synergistic effect of photons localization of photonic crystals and the sensitization of CdS quantum dots

In this work, the enhancement of TiO2 photocatalytic activity was studied through synergistic effect of the photons localization of photonic crystals and the sensitization of CdS quantum dots (CdS QDs). CdS QDs sensitized TiO2 membrane (denoted as CdS QDs/TiO2) was synthesized through doping the TiO2 membrane with CdS QDs by chemical bath deposition method (CBD). After TiO2 was sensitized with CdS QDs, the edge of light absorption of TiO2 was red-shifted to 470nm and the light absorption in the range of 400600nm was higher than that of plain TiO2 membrane. Another type of composite membrane, CdS QDs/TiO2/SiO2 opal composite membrane was prepared by coupling SiO2 opal (a kind of photonic crystal) layer onto the CdS QDs/TiO2 membrane, and the photonic band gap of the SiO2 opal photonic crystal layer was deliberately planned at the electronic band gap of the CdS QDs. The photodegradation of gaseous CH3CHO (acetaldehyde) was used as probe reaction to test the photocatalytic activity of the as-prepared membranes, and the results showed that the CdS QDs sensitization can significantly improve the photocatalytic activity of TiO2 membrane under visible light irradiation, with the acetaldehyde degradation rate constant (k) on CdS QDs/TiO2 membranes being 1.59 times of that on plain TiO2 membranes. The acetaldehyde degradation rate constant on CdS QDs/TiO2/SiO2 opal composite membrane reached 4 times of that on plain TiO2 membrane. The photocatalytic activity of TiO2 membrane can be improved through synergistic effect of the photons localization of photonic crystals and the sensitization of CdS QDs.

Two-dimensional function photonic crystal

Photonic crystal is a kind of periodic optical nanostructure consisting of two or more materials with different dielectric constants, which has attracted great deal of attention because of its wide range of potential applications in the field of optics. Photonic crystal can be fabricated into one-, or two-, or three- dimensional one. Among them, the two-dimensional photonic crystal turns into a hot focus due to its fantastic optical and electrical properties and relatively simple fabrication technique. Since the tunable band gaps of two-dimensional photonic crystals are beneficial to designing the novel optical devices, to study their optical and electrical properties for controlling the electromagnetic wave is quite valuable in both theoretical and practical aspects. In this work, we propose a new type of two-dimensional function photonic crystal, which can tune the band gaps of photonic crystals. The two-dimensional function photonic crystal is different from the traditional photonic crystal composed of medium columns with spatially invariant dielectric constants, since the dielectric constants of medium column are the functions of space coordinates. Specifically, the photorefractive nonlinear optical effect or electro-optic effect is utilized to turn the dielectric constant of medium column into the function of space coordinates, which results in the formation of two-dimensional function photonic crystal. We use the plane-wave expansion method to derive the eigen-equations for the TE and TM mode. By the Fourier transform, we obtain the Fourier transform form (G) for the dielectric constant function (r) of two-dimensional function photonic crystal, which is more complicated than the Fourier transform in traditional two-dimensional photonic crystal. The calculation results indicate that when the dielectric constant of medium column is a constant, the Fourier transforms for both of them are the same, which implies that the traditional two-dimensional photonic crystal is a special case for the two-dimensional function photonic crystal. Based on the above theory, we calculate the band gap structure of two-dimensional function photonic crystal, especially investigate in detail the corresponding band gap structures of TE and TM modes. The function of dielectric constant can be described as (r) = kr + b, in which k and b are adjustable parameters. Through comparing the calculation results for both kinds of photonic crystals, we can find that the band structures of TE and TM modes in two-dimensional function photonic crystals are quite different from those in traditional two-dimensional photonic crystal. Adjusting parameter k, we can successfully change the number, locations and widths of band gaps, indicating that the band gap structure of two-dimensional function photonic crystal is tunable. These results provide an important design method and theoretical foundation for designing optical devices based on two-dimensional photonic crystal.

Reflection phase characteristics and their applications based on one-dimensional coupled-cavity photonic crystals with gradually changed thickness ofsurface layer

In this paper, we first improve the traditional transfer matrix method to adapt to one-dimensional photonic crystal consisting of arbitrary materials, and then use it to study the reflection phase characteristics of two kinds of photonic crystals, i.e., a simple periodic photonic crystal structure and a coupled-cavity asymmetric photonic crystal with gradually changed thickness of surface layer. For both of the structures, the reflectivity within photonic band gap is above 98% and hardly affected by the thickness of the surface layer. However, their reflection phases exhibit distinctly different properties. For the simple photonic crystal structure, the reflection phases of both TE and TM polarizations are sensitively dependent on the thickness of surface layer, but their phase difference is almost the same as the thickness of surface layer varies, which cannot change the polarization of reflected light. While for the coupled-cavity asymmetric photonic crystal structure, studies show that the degenerate defect modes within photonic band gap will split as the thickness of the surface layer varies. Moreover, around the splitting defect modes the reflection phases of both TE and TM polarizations, as well as their phase difference, are sensitively dependent on the thickness of surface layer, resulting in sensitive polarization change of reflected light. The physical reason is attributed to the dramatic phase change caused by the splitting of degenerate defect modes. The above reflection phase characteristics of coupled-cavity asymmetric photonic crystals have potential in lowering or even eliminating the coherence of lasers in some special application cases. As an example, we design a one-dimensional photonic crystal structure with two-dimensional periodic varying thickness of surface layer. After an oblique incident narrowband laser beam is reflected from this structure and then focused by a lens, various polarized light beams (including linear polarized light beams along different directions, left-hand (or right-hand) circular (or elliptical) polarized light beams) will exist simultaneously, whose superposition will produce optical field with random phase and polarizations in the focal region. These results can effectively reduce the coherence of lasers, which holds promise in many fields such as laser nuclear fusion.

Fabrication and Characterization of Photonic Crystals in Photopolymer SZ2080 by Two-Photon Polymerization Using a Femtosecond Laser

Two-photon polymerization (2PP) is a powerful technique in fabricating three-dimensional subdiffraction-limited structures. In this paper, 2PP was applied to generate woodpile structures, one kind of photonic crystal, using SZ2080, which is widely used in 2PP due to its negligible shrinkage. First, the relationship between scanning speed, laser power, and resolution was determined through fabricating free-hanging lines by theoretical and experimental study. Based on this relationship, woodpile structures with different period distances were fabricated with high uniformity as shown by scanning electron microscopy (SEM) images. Then optical properties of woodpile structures were investigated using Fourier transform infrared spectroscopy (FTIR) and a quantitative empirical relationship between period distance and band gaps was established. The empirical relationship can be applied to design woodpile photonic crystals for the optical sensors and filters.

Photonic Bandgap Tuning of Photonic Crystals by Air Filling Fraction

In this paper, the type of photonic crystals (PCs) which consists of air holes surrounded by silica as a background with square lattice arrangement in two dimension (2D) has been assumed. A plane wave expansion method (PWEM) is implemented to calculate the photonic band structure of this kind of PC, then the effect of changing air filling fraction is studied on the photonic band structure diagram, by changing the air hole radius and lattice constant (a). As a result, a tuning and shifting of the photonic bandgaps (PBGs) has been obtained.

Frequency characteristics of electromagnetic bandgap structure with bow‐tie cells and its optimal design based on particle swarm optimization

AbstractThe electromagnetic bandgap (EBG) structure, which is widely used in the microwave and millimeter‐wave fields, is a kind of photonic crystal. An EBG structure with bow‐tie cells having different tapered forms is presented in this paper. Furthermore, the EBG structure is optimized by using an improved particle swarm optimization algorithm. The optimal results show that the optimized EBG structure with bow‐tie cells has a good stop‐band performance and large relative bandwidth. The passband ripples of the EBG structure are very small and basically symmetrical. The frequency characteristic of the optimized EBG structure is found to be excellent. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Comparative study of photonic band gaps of germanium-based two-dimensional triangular-lattice and square-lattice and decagonal quasi-periodic photonic crystals

Photonic band gaps (PBGs) of germanium-based two-dimensional (2D) triangular-lattice and square-lattice and decagonal quasi-periodic photonic crystals (PCs) with the scatterer radius in the range of [0,0.3a] and within two cases of the construction (germanium cylinders being placed in air, air cylinders being placed in germanium) have been calculated by using the plane wave expansion (PWE) method. Germanium-based 2D triangular-lattice PC and 2D decagonal quasi-periodic PC are more easily to generate PBG than 2D square-lattice PC. 2D decagonal quasi-periodic PC is more easily to generate complete band gap than the other two kinds of PCs. The PBG properties of the three PCs are similar to the properties of silicon-based system as the radius of the scatterer cylinder increases. Nevertheless, the germanium-based system is more likely to generate PBG than silicon-based system. These findings will guide the design of PBG-type microstructure devices.

Optically switchable photonic crystals based on inverse opals partially infiltrated by photoresponsive liquid crystals

We demonstrate optically switchable photonic crystals based on SiO2 inverse opals infiltrated with photoresponsive liquid crystals. The optical properties of the hybrid organic/inorganic structure were characterized by measuring reflectance spectra. The Bragg reflection of the photonic crystal, i.e. photonic band gap, can be switched upon UV photoirradiation. The physical mechanism underlying this switchable behavior is the nematic–isotropic phase transition of the liquid crystals inside the opals triggered by the trans–cis isomerization of the photochromic liquid crystal molecules, resulting in a change of the refractive index contrast between the liquid crystal and the SiO2 inverse opal. The experimental results are in excellent agreement with the analytical calculations. With advantages in cost-effective fabrication, easy integration, and all-optical control, this kind of photonic crystals could find many active photonic applications.