Photonic Band Gap Properties Research Articles

Photonic-Plasmonic Hybrid 2D-Pillar Cavity for Mode Confinement With Subwavelength Volume

We present a two-dimensional photonic-plasmonic hybrid cavity design by exploring the photonic bandgap properties and the plasmonic characteristics. The FDTD simulation tool was used to optimize the cavity parameters. The design was achieved by introducing a layer of defect rods in the 2D-PhC pillar structure on a thin metal slab supported by a glass substrate. The excited defect mode is confined in the photonic-plasmonic bandgap, it is spatially restricted on the symmetry plane and the plasmonic characteristics offer enhanced confinement in the vertical plane close to the metal layer. The optimized size of the defect rods as well as the thickness of the metal layer can offer an enhanced Q factor of 850, and subwavelength mode volume of 0.07 ( $\lambda $ /n)3 with a maximum intensity distribution is concentrated in the defect rods.

Photonic bandgap properties of two dimensional photonic quasicrystals with multiple complex structures

Abstract Two dimensional photonic quasicrystals (PQCs) with different rotational symmetries are constructed based on holographic interference patterns. Their photonic bandgap (PBG) properties are obtained by using finite element method (FEM) to calculate the transmission and reflection spectra with different directions. The maximum gap-midgap ratio among different dielectric constant contrast and fill factor is given for all the PQCs to compare their abilities to produce bandgaps. The results show that 10-fold (five beams interference) and 12-fold quasicrystals are easier to form bandgaps than others. This may provide a reference to select appropriate quasicrystal structures for photonic devices and optimize device performance.

Manipulation of Bragg and graphene photonic band gaps in one-dimensional photonic crystal containing graphene

Using the Kronig-Penney method, we have investigated the photonic band gap properties of one-dimensional photonic crystal composed of dielectric and multilayer dielectric-graphene layers in terahertz frequency region for both electric and magnetic polarizations. The computational results represent two kinds of photonic band gaps (i.e. Bragg and graphene), and the effect of incident angle and chemical potential of graphene nanolayers are investigated on these photonic band gaps. The obtained results show that the width of both band gaps are more influenced by changing the chemical potential of graphene, but the incident angle has little effect. The proposed PC structure can be used for designing tunable optical devices in the terahertz frequency range.

Design of photonic crystal based optical digital to analog converters

The future of telecommunication and optical communication networks is extremely focused on the design and development of photonic integrated circuits (PICs). Photonic crystals play the foremost role in realizing all optical integrated circuits. Every single optical component required to be integrated in PICs can be outlined based on the requirement of the application and can be obtained with the photonic band gap property of photonic crystals. Numerous works on different optical components has been done using photonic crystals. Among which, optical digital-to-analog converters (DACs) need to be explored and attended to incorporate into PICs. In this paper, photonic crystal-based 1-bit and 2-bit DACs, suitable for the photonic integrated circuits application, are proposed. Photonic crystal ring resonators and waveguides were integrated into the reported structures. The Kerr effect of the ring resonators has been utilized to provide an average error of 4.8477% for a 2-bit optical DAC. The devised structure provides an insertion loss of −5.5596 dB, with an overall dimension of 358 µm2. The DAC structures were simulated using finite difference time domain and plane wave expansion methods.

Upconversion fluorescence enhancement of NaYF4:Yb/Re nanoparticles by coupling with SiO2 opal photonic crystals

Upconversion fluorescent material such as NaYF4:Yb/Re (Re is lanthanide ions) nanoparticles has considerable application prospect, but the fluorescence efficiency is usually too low. In this paper, an effective approach has been validated to enhance the fluorescence intensity of NaYF4:Yb/Re by coupling with SiO2 opal photonic crystals (PCs). NaYF4:Yb/Tm and NaYF4:Yb/Er were prepared by thermal decomposition method and ligand exchange, and then spin-coated on the surface of SiO2 opal PCs with different photonic band gap (PBG). The PBG properties of PCs/UCNPs composite films were measured by transmission spectra. The effect of overlapping extent between PBG and UCNPs’ emission on upconversion emission enhancement was studied through fluorescence spectra. The result shows that when the SiO2 opal PCs with the PBG at 448 nm were composited with NaYF4:Yb/Tm, the upconversion fluorescence at 450 nm was enhanced mostly, which is 34-fold. Similarly, the highest enhancement, 23-fold, was observed for fluorescence of NaYF4:Yb/Er at 541 nm when composited with SiO2 opal PCs having PBG at 544 nm. According to the analysis, the upconversion fluorescence can be enhanced through coupling with PCs by utilizing the light reflection and light localization effect of PCs. At the same time, the highest enhancement is obtained when the PBG of PCs is exactly overlapping with the wavelength of upconversion fluorescence. Our study potentially will contribute to promoting the sooner practical application of upconversion nanoparticles.

Photonic band gap of multiferroic-dielectric materials in the IR region: FDTD method

In this report, we present an investigation of the optical properties and band structure calculations for the photonic structures based on the multiferroic materials- BaMnF4. We calculate the photonic bands and optical properties of BaMnF4/LiNbO3 based photonic crystal. We study the photonic band gap and optical properties of the photonic structures, numerically analyzed in the IR frequency region by using the FDTD method for various incidence angles, number of periods in the PC and the nature/geometry of the materials.

Tuning full photonic band gap with plasma frequency in two-dimensional photonic crystals composed of anisotropic dielectric rods in plasma background

In this study, we analyze full photonic band gap formation and properties of two-dimensional photonic crystals with square lattice, composed of anisotropic tellurium rods with different geometric shapes in a plasma background. Using the finite-difference time-domain method, we discuss the tunability of the full photonic band gap width as a function of the plasma frequency for different values of tellurium rod’s parameters. The calculated results show that our proposed structures represent full photonic band gaps with considerable width, which are dependent on plasma frequency.

Optical Performance Study of Gyroid‐Structured TiO2 Photonic Crystals Replicated from Natural Templates Using a Sol‐Gel Method

AbstractPhotonic crystals with novel nanostructures have attracted huge attention due to their potential applications in manipulation of light propagation and next‐generation energy and information technologies. In this work, TiO2 photonic crystals with 3D bicontinuous gyroid structure in visible light wavelength range are successfully fabricated by templating from natural templates using a sol‐gel method. This is the first time to report controlling the volume fraction (VF) through regulating the rinsing time of templates in the sol‐gel precursor. Gyroid‐structured TiO2 photonic crystals (GTPCs) with different VFs, 3.2, 8.0, and 13.5% are obtained. Combined with finite‐difference time‐domain simulations, the photonic bandgap properties of the GTPCs are systematically studied. Based on this work, one step is moved further toward the exploitation of the optical performance of the GTPCs in visible light wavelength range beyond the previous simulation works.

Multichannel tunable omnidirectional photonic band gaps of 1D ternary photonic crystal containing magnetized cold plasma

By using the transfer matrix method, theoretical investigations have been carried out in the microwave region to study the reflection properties of multichannel tunable omnidirectional photonic bandgaps (OPBGs) based on the magneto-optic Faraday effect. The proposed one dimensional ternary plasma photonic crystal consists of alternate layers of quartz, magnetized cold plasma (MCP), and air. In the absence of an external magnetic field, the proposed structure possesses two OPBGs induced by Bragg scattering and is strongly dependent on the incident angle, the polarization of the incident light, and the lattice constant unlike to the single-negative gap and zero-n¯ gap. Next, the reflection properties of OPBGs have been made tunable by the application of external magnetic field under right hand and left hand polarization configurations. The results of this manuscript may be utilized for the development of a new kind of tunable omnidirectional band stop filter with ability to completely stop single to multiple bands (called channels) of microwave frequencies in the presence of external static magnetic field under left-hand polarization and right-hand polarization configurations, respectively. Moreover, outcomes of this study open a promising way to design tunable magneto-optical devices, omnidirectional total reflectors, and planar waveguides of high Q microcavities as a result of evanescent fields in the MCP layer to allow propagation of light.

The Mie resonance and dispersion properties in the two-dimensional superconductor photonic crystals with fractal structure

In this paper, the Mie resonance and dispersion properties in the two-dimensional (2D) superconductor photonic crystals (SPCs) with fractal structure under a transverse-magnetic (TM) wave are theoretically investigated by a modified plane wave expansion method, whose equations of calculations also are deduced. The configuration of 2D SPCs is the dielectric rods embedded into the superconductor Nb background with square lattices according to the iteration rule of Thue-Morse sequence (Th-MS). The calculated density of states and band structures are used to elaborate the Mie resonance in the proposed SPCs and the properties of photonic band gap (PBG) and defect mode, and the influences of configurational parameters on the dispersion properties are studied in detail as well. The calculated results demonstrate that the lower edge of PBG is flattened, which is originated from the Mie resonance, and two defect modes (quasi-localized states) appear in the PBG since Th-MS has the self-similarity and non-periodicity at the same time. The PBG and defect modes can be obviously trimmed off by changing those parameters.

Photonic and phononic surface and edge modes in three-dimensional phoxonic crystals

We investigate the photonic and phononic surface and edge modes in finite-size three-dimensional phoxonic crystals. By appropriately terminating the phoxonic crystals, the photons and phonons can be simultaneously guided at the two-dimensional surface and/or the one-dimensional edge of the terminated crystals. The Bloch surface and edge modes show that the electromagnetic and acoustic waves are highly localized near the surface and edge, respectively. The surface and edge geometries play important roles in tailoring the dispersion relations of the surface and edge modes, and dual band gaps for the surface or edge modes can be simultaneously achieved by changing the geometrical configurations. Furthermore, as the band gaps for the bulk modes are the essential prerequisites for the realization of dual surface and edge modes, the photonic and phononic bulk-mode band gap properties of three different types of phoxonic crystals with six-connected networks are revealed. It is found that the geometrical characteristic of the crystals with six-connected networks leads to dual large bulk-mode band gaps. Compared with the conventional bulk modes, the surface and edge modes provide a new approach for the photon and phonon manipulation and show great potential for phoxonic crystal devices and optomechanics.

Photonic band gap properties of one-dimensional Thue-Morse all-dielectric photonic quasicrystal

In this paper, the photonic band gap (PBG) properties of one-dimensional (1D) Thue-Morse photonic quasicrystal (PQC) S4 structure are theoretically investigated by using transfer matrix method in Bragg condition. The effects of the center wavelength, relative permittivity and incident angle on PBG properties are elaborately analyzed. Numerical results reveal that, in the case of normal incidence, the symmetry and periodicity properties of the photonic band structure are presented. As the center wavelength increases, the PBG center frequency and PBG width decrease while the photonic band structure is always symmetrical about the central frequency and the photonic band structure repeats periodically in the expanding observation frequency range. With the decrease of relative permittivity contrast, the PBG width and the relative PBG width gradually decreases until PBG disappears while the symmetry of the photonic band structure always exists. In the case of oblique incidence, as the incident angle increases, multiple narrow PBGs gradually merge into a wide PBG for the TE mode while for the TM mode, the number of PBG continuously decreases and eventually disappears, i.e., multiple narrow PBGs become a wide passband for the TM mode. The research results will provide a reference for the choice of the material, the incident angle for the PBG properties and its applications of 1D Thue-Morse PQC.

Biodegradable Inverse Opals with Controlled Discoloration

AbstractColloidal crystals and their derivatives possess photonic bandgap property, being useful in various applications, including structural coloration and colorimetric sensing. In this work, inverse opals made of a biodegradable polymer, poly(lactic‐co‐glycolic acid) (PLGA), are prepared to provide a controlled discoloration. To make PLGA inverse opals, a monolayer of silica particles is first deposited on the surface of PLGA film by spin coating, which is then partially embedded into the film by thermal annealing. Opal is deposited on the monolayer‐coated PLGA film by dip coating and then embedded into the underlying PLGA film. Selective removal of silica particles leaves behind a face‐centered cubic lattice of air cavity in PLGA matrix. The inverse opals whose framework is made of PLGA exhibit a pronounced structural color in dried state. When they are subjected to water, PLGA degrades by hydrolysis of ester groups, which results in the gradual discoloration. The discoloration rate is controllable by varying the pH of surrounding medium and cavity sizes, so that it can act as a colorimetric indicator of valid periods for drugs, foods, and cosmetics. In addition, high biocompatibility and unique optical appearance further render the inverse opals useful as edible anticounterfeiting materials for valuable drugs.

Preparation and magnetic properties of magnetic photonic crystal by using monodisperse polystyrene covered Fe3O4 nanoparticles onto glass substrate

Engineering approach towards combined photonic band gap properties and magnetic/polymer composite particles, attract considerable attention of researchers due to their unique properties. In this research, two different magnetic particles were prepared by nearly monodisperse polystyrene spheres as bead with two concentrations of Fe3O4 nanoparticles to prepare magnetic photonic crystals (MPCs). The crystal surfaces and particles morphology were investigated employing scanning electron microscopy and transmission electron microscopy. The volume fraction of magnetic material embedded into colloidal spheres and their morphology was found to be a key parameter in the optical and magneto-optical properties of transparent MPC.

Controlled Insertion of Planar Defect in Inverse Opals for Anticounterfeiting Applications.

Inverse opals have been used for structural coloration and photonic applications owing to their photonic bandgap properties. When the photonic structures contain planar defects, they provide defect modes, which are useful for lasing, sensing, and waveguiding. However, it remains a challenge to insert a planar defect into inverse opals in a reproducible manner. Here, we report a new method for producing planar-defect-inserted inverse opals using sequential capillary wetting of colloidal crystals and creating micropatterns through photolithography. Three cycles of deposition and thermal embedding of colloidal crystals into the underlying film of negative photoresist were performed. In the three cycles, opal, particle monolayer, and opal were sequentially employed, which yielded the monolayer-templated planar defect sandwiched by two inverse opals after particle removal. The planar defect provided a passband whose wavelength can be controlled by adjusting the diameter of particles for the defect layer. Moreover, the defect-inserted inverse opals can be micropatterned by photolithography as the negative photoresist is used as a matrix. The resulting micropatterns deliver a unique spectral code featured by a combination of stop band and defect mode and a graphical code dictated by photolithography, being useful for anticounterfeiting applications.

Investigation of TE-polarized photonic band gap properties in matallodielectric photonic crystals composed of metal coated dielectric cylinders

Using the Dirichlet-to-Neumann map method and generalization of this method, we have been able to calculate the photonic band structure of two-dimensional (2D) metallodielectric photonic crystals composed of metal-coated circular dielectric rods. The rods are embedded in an air background with a square array. We are interested in considering transverse electric (TE) mode of electromagnetic waves. The resulting band structures show the existence of photonic band gaps as well as some flat band regions. We theoretically study the effect of the dielectric constant and radius of the dielectric core on the photonic band structures. There are some interesting results compared to the case of solid metallic rods (without dielectric core) such as appearing the new photonic band gaps and a flat band region with the characteristic of cavity modes.

Photonic Bandgap Properties of One-Dimensional Graphene-Based Photonic Crystals with a Single Dielectric

The transfer matrix method was used to investigate the photonic bandgap properties of one-dimensional graphene-based photonic crystal (GPC) with a single dielectric medium. The first layer of the unit cell of the GPC consists of a traditional dielectric medium and the second is the same dielectric medium wherein graphene sheets are embedded. Numerical calculation results show that the width of the low frequency bandgap decreases as the period of the GPC, the permittivity of the dielectric, the thickness of the dielectric layer, the filling factor of the dielectric layer, and the period of the graphene-dielectric multilayer medium structure increase and increases as the thickness of the graphene-dielectric multilayer medium structure increases. The influence of the above parameters on the Bragg bandgap is different from their effects on the low frequency bandgap. Due to the graphene conductivity could be tuned by varying the chemical potential, so GPC is a tunable PC and may have many potential applications in photonics.

Investigations on the two-dimensional aperiodic plasma photonic crystals with fractal Fibonacci sequence

In this paper, the properties of photonic band gaps (PBGs) and defect modes of two-dimensional (2D) fractal plasma photonic crystals (PPCs) under a transverse-magnetic (TM) wave are theoretically investigated by a modified plane wave expansion (PWE) method. The configuration of 2D PPCs is the square lattices with the iteration rule of the Fibonacci sequence whose constituents are homogeneous and isotropic. The proposed 2D PPCs is filled with the dielectric cylinders in the plasma background. The accuracy and convergence of the present modified PWE method also are validated by a numerical example. The calculated results illustrate that the enough accuracy and good convergence can be achieved compared to the conventional PWE method, if the number of meshed grids is large enough. The dispersion curves of the proposed PPCs and 2D PPCs with a conventional square lattice are theoretically computed to study the properties of PBGs and defect modes. The simulated results demonstrate that the advantaged properties can be obtained in the proposed PPCs compared to the 2D conventional PPCs with similar lattices. If the Fibonacci sequence is introduced into the 2D PPCs, the larger PBGs and higher cutoff frequency can be achieved. The lower edges of PBGs are flat, which are originated from the Mie resonances. The defect modes can be considered as the quasi-localized states since the Fibonacci sequence has the self-similarity and non-periodicity at the same time. The effects of configurational parameters on the characters of the present PPCs are investigated. The results show that the PBGs and defect modes can be easily manipulated by tuning those parameters.

Preferential self-assembly behavior of polydisperse silica particles under negative pressure

The research about assembly behavior of colloidal particles under external field is a key of improved self-assembly method. Although high quality photonic crystals prepared by improved self-assembly method under external field have been reported, real applications require monodisperse particles. Here, we designed negative pressure field to prepare opal film composed of polydisperse SiO2 particles. The effect of different negative pressures on the opal’s surface morphology and photonic band gap (PBG) properties was investigated. Under the optimal pressure, close-packed opal was obtained, which is composed of irregular and polydisperse silica particles. We attribute this to the balance between sedimentation of SiO2 particles and solvent evaporation during the assembly process. Importantly, this approach could be complementary to the preparing of three-dimensional photonic crystals with long-range ordered structures in usual laboratory.

Effect of sequence built on photonic band gap properties of one-dimensional quasi-periodic photonic crystals: Application to Thue-Morse and Double-period structures

We elaborated by Radio frequency magnetron sputtering two types of one-dimensional quasi-periodic photonic crystals, based on Si/SiO2 materials, according to the Thue-Morse sequence and the Double-period one. We have investigated their optical properties, throughout the reflection transmission spectra, experimentally as well theoretically by using the transfer matrix method. The experimental spectra of these two structures are performed at normal incident light configuration, in the near infrared wavelengths range, and, are compared for the same number of layers, for a generation number N varying from 0 to 5, corresponding to a number of layers varying from 1 to 32, respectively. We experimentally put in evidence the appearance of photonic band gaps for N higher than 2, which are then well defined for N equal to 4, for the two structures. Furthermore, the results show that these two quasi-periodic structures exhibit sharp localized modes of light within the photonic band gaps, covering the optical telecommunication wavelengths 1.33 and 1.55 μm, with different number and position depending, on the built in distribution structures. The results also show a good agreement between the experimental and calculated spectra.