Omnidirectional Band Research Articles

INVESTIGATION OF ULTRA-WIDE REFLECTION BANDS IN UV REGION BY USING ONE-DIMENSIONAL MULTI QUANTUM WELL PHOTONIC CRYSTAL

Enhancement of the reflection bands in ultraviolet region by using one-dimensional multi quantum well (MQW) photonic crystal (PC) structure has been investigated theoretically. The proposed structure is composed of three MgF2/SrTiO3 MQWs. The range of reflection band is investigated from the reflectance spectra of the one-dimensional MQW photonic crystal structure obtained by Transfer Matrix Method (TMM). From the numerical analysis it is observed that a range of reflection band for a single MQW PC is very narrow though it increases as the thickness of layers increases. But when three MQWs of MgF2/SrTiO3 are used we get much enlarged reflection band covering the range 119.8 nm- 311.3 nm (reflectivity > 99%) with bandwidth 191.5 nm, for normal incidence. Further, we see that when the angle of incidence is increased, the width of reflection band increases in case of TE wave with a decrease for TM wave, because this omnidirectional reflection (ODR) band is very much narrow in UV region. We have computed ODR band upto incidence angle 50 ◦ for single as well as combined MQW PC. Analyzing the reflectance curve for incidence angle up to 50 ◦ for both TE and TM polarizations we find that by applying the combined MQW PC, omnidirectional reflection band increases significantly in comparison to single MQW structure. The proposed MQW photonic crystal structure is very useful in designing ultraviolet shielding for drugs, ultraviolet reflector for protecting damage of DNA and in skin diseases especially for skin cancer.

Enlargement of the omnidirectional reflectance gap in one-dimensional photonic crystal heterostructure containing double negative index material

In this paper, we investigate by theoretical analysis a way to enlarge the frequency range of band gap in one-dimensional heterostructure photonic crystal (PC) made of two PCs alternate stacked by conventional and double negative index material. The numerical results by scattering matrix method (SMM) show that, for the proposed PC with appropriate parameters, there is an omnidirectional photonic band gap (OBG), which is insensitive to incident angle and polarization. The thickness ratio of layers in the second PC is the inverse and identical of that in the first PC, respectively. Two PCs form the PC heterostructures. Moreover, we demonstrate the existence of OBG and notable enlargement of the frequency range of the OBG in proposed PC heterostructure. The reason is that the pass band of one of the two PCs falls into the forbidden band of another PC. Decreasing the thickness of layers but not changing the thickness ratio of layers in the second PC, the frequency range of OBG keeps invariant. However, with the increasing of thickness of layers, the frequency range of OBG gets narrow.

Étude comparative des plaques verrouillées anatomiques (3,5 mm versus 4,5 mm) dans le traitement des fractures articulaires de l’extrémité proximale du tibia

In this paper, the first two total omnidirectional photonic band gaps (OBGs) of one-dimensional (1D) superconductor–dielectric photonic crystals (SDPCs) which composed of dielectric–dielectric and superconductor–dielectric periodic structures have been investigated theoretically by using the transfer matrix method (TMM). Those OBGs originate from Bragg gaps. From the analysis, it is found that this kind of heterostructure has wider frequency ranges of total OBGs for both polarizations in comparison to the dielectric photonic crystals (DPCs) or SDPCs, and the bandwidths of OBGs can be notably enlarged by increasing the thickness of superconductor layer and decreasing the ambient temperature.

Enlarged omnidirectional photonic band gap in one-dimensional ternary plasma photonic crystals based on a new Thue–Morse aperiodic structure

In this paper, an omnidirectional photonic band gap (OBG) realized by one-dimensional ternary non-magnetized plasma dielectric photonic crystals (PPCs) based on a new Thue–Morse aperiodic structure, is studied by the transfer matrix method. From the numerical results, the OBG can be enlarged by manipulating the plasma thickness and density, but ceases to change with increasing Thue–Morse order. However, the plasma collision frequency has no effect on the OBG. It is clear that such new one-dimensional ternary PPCs have a superior feature in the enhancement of OBG compared with the conventional ternary and conventional ternary Thue–Morse aperiodic PPCs.

Enlarged the omnidirectional Bragg gap by one-dimensional superconductor-dielectric photonic crystals with ternary Thue–Morse aperiodic structure

In this paper, an omnidirectional photonic band gap (OBG) which originates from Bragg gap compared to zero-n˜ gap or single negative (negative permittivity or negative permeability) gap, is realized by one-dimensional (1D) superconductor-dielectric photonic crystals (SDPCs) with ternary Thue–Mores aperiodic structure, which is composed of superconductor and two kinds of homogeneous, isotropic dielectric is theoretically investigated by the transfer matrix method (TMM) in detail. Such OBG is insensitive to the incident angle and the polarization of electromagnetic wave (EM wave). From the numerical results, the bandwidth and central frequency of OBG can be notably enlarged by tuning the thickness of superconductor and dielectric layers but cease to change with increasing Thue–Mores order. The OBG also can be manipulated by the ambient temperature of system especially close to the critical temperature. Moreover, the damping coefficient of superconductor has no effect on the bandwidth of OBG under low-temperature condition. These results may provide theoretical instructions to design the future optoelectronic devices based on superconductor.

Omnidirectional Photonic Band Gap in One-Dimensional Ternary Superconductor-Dielectric Photonic Crystals Based on a New Thue–Morse Aperiodic Structure

In this paper, an omnidirectional photonic band gap (OBG) of one-dimensional (1D) ternary superconductor-dielectric photonic crystals (SDPCs) based on a new Thue–Mores aperiodic structure is theoretically studied by the transfer matrix method (TMM) in detail. Compared to zero- $\bar{n}$ gap or single negative (negative permittivity or negative permeability) gap, such OBG originates from Bragg gap. From the numerical results, the bandwidth and central frequency of OBG can be notably enlarged by manipulating the thicknesses of superconductor and dielectric layers but cease to change with increasing the Thue–Mores order. The OBG also can be tuned by the ambient temperature of the system especially close to the critical temperature. However, the damping coefficient of the superconductor layer has no effects on the OBG. The relative bandwidth of OBG also is investigated by the parameters as mentioned above. It is clear that such 1D ternary SDPCs have a superior feature in the enhancement of the bandwidth of OBG compared to the conventional ternary SDPCs and conventional ternary Thue–Mores aperiodic SDPCs. These results may provide theoretical instructions to design the future SDPCs devices.

Enlargement of the omnidirectional photonic band gap by one-dimensional plasma-dielectric photonic crystals with fractal structure

In this paper, an omnidirectional photonic band gap (OBG) which originates from Bragg gap compared to \(\text{ zero- }\overline{n}\) gap or single negative (negative permittivity or negative permeability) gap, realized by one-dimensional plasma-dielectric photonic crystals with fractal structure (Thue–Mores aperiodic structure), which is composed of plasma and one kind of homogeneous, isotropic dielectric is theoretically studied by the transfer matrix method in detail. Such OBG is insensitive to the incident angle and the polarization of electromagnetic wave. From the numerical results, the bandwidth and central frequency of OBG can be notably enlarged by tuning the thickness of plasma and dielectric layers but cease to change with increasing the Thue–Mores order. The OBG also can be manipulated by the plasma density. Moreover, the plasma collision frequency has no effect on the bandwidth of OBG.

A broadband omnidirectional absorber based on a hetero-structure composed of a collision plasma and a ternary plasma Bragg mirror

A broadband omnidirectional absorber which is realized by heterostructures containing a collision plasma layer and a ternary plasma Bragg mirror is theoretically investigated. A collision plasma layer and an appropriate dielectric layer are put on the top of the ternary plasma photonic crystals to obtain a broadband omnidirectional absorption. It is shown to absorb roughly 70% of all available electromagnetic wave in a relative omnidirectional absorption band width 0.58 GHz with plasma width 3 mm in PCs. The band edges are impacted by the range of reflection band gap and the absorption range for transverse magnetic (TM) wave decreases at large incidence. Compared with some previous designs, our proposed structure has a relative flatter total absorption spectrum over a broad frequency range in microwave. This kind of hererostructures offer additional opportunities to design novel optoelectronic devices.

Investigating the Omnidirectional Photonic Band Gap in One-Dimensional Superconductor–Dielectric Photonic Crystals with a Modified Ternary Fibonacci Quasiperiodic Structure

In this paper, an omnidirectional photonic band gap (OBG) of one-dimensional (1D) superconductor–dielectric photonic crystals (SDPCs) with a modified ternary Fibonacci quasiperiodic structure which originates from Bragg gap is theoretically investigated by the transfer matrix method (TMM) in detail. The SDPCs are composed of superconductor and two kinds of homogeneous, isotropic dielectric. Such OBG is independent of the incidence angle and the polarization of electromagnetic wave (EM wave). From the numerical results, the OBG can be notably enlarged by tuning the thickness of superconductor and dielectric layers but cease to change with increasing the Fibonacci order. The OBG also can be manipulated by the ambient temperature of system. Especially, the ambient temperature of system is close to the critical temperature. However, the damping coefficient of superconductor has no effects on the OBG. The gap/midgap ratio of OBG also is studied by those parameters. It is shown that 1D SDPCs with a modified ternary Fibonacci quasiperiodic structure have a superior feature in the enhancement of OBG compared with the conventional 1D ternary and conventional ternary Fibonacci quasiperiodic SDPCs.

Omnidirectional photonic band gaps enhanced by Fibonacci quasiperiodic one-dimensional ternary plasma photonic crystals

An omnidirectional photonic band gap realized by one-dimensional Fibonacci quasiperiodic structure which is composed of plasma and two kinds of isotropic dielectric is theoretically studied. It has been shown that such an omnidirectional photonic band gap is insensitive to the incident angle and the polarization of electromagnetic wave (EM wave). The frequency range and central frequency of omnidirectional photonic band gap cease to change with increasing Fibonacci order, but vary with the thickness and density of the plasma. The bandwidth of omnidirectional photonic band gap can be notably enlarged. The omnidirectional photonic band gap originates from a Bragg gap in contrast to zero-n˜ gap or single negative (negative permittivity or negative permeability) gap. From the numerical results performed by the transfer matrix method (TMM), it has been proved that Fibonacci quasiperiodic one-dimensional ternary plasma photonic crystals have a superior feature in the enhancement of omnidirectional photonic band gap frequency range compared with the conventional ternary plasma photonic crystals. This omnidirectional photonic band gap has potential applications in filters, microcavities, and fibers, etc.

Optical reflectance and omnidirectional bandgaps in Fibonacci quasicrystals type 1-D multilayer structures containing exponentially graded material

A theoretical study of optical reflectance and reflection bands of 1-D photonic quasi-crystals (Fibonacci type arrangement) composed of exponentially graded material is presented. The proposed structures consist of two different layers, one of them is of constant refractive index (L) and the other one is of exponentially graded refractive index (S) dielectric materials. Four different generations (2nd, 3rd, 4th and 5th) of the Fibonacci sequence for 10 periods in one dimension (1-D) are considered and compared in view of their optical reflectance and bandgaps for both TE and TM polarisations. Also, we proposed some heterostructures made by the combination of different Fibonacci generations and their periods to obtain suitable omnidirectional reflection band. We used the transfer matrix method (TMM) to obtain the reflectance, bandgaps and omnidirectional reflectional bandgaps (ODR) of such structures in near infrared spectrum (800–2200nm) at different angles of incidence. We show that ODR exists in these types of structures. The number of ODRs and total bandgap depend on the Fibonacci generations. Extraordinary ODR bandgaps are obtained in the case of heterostructures formed by the combination of different generations of the Fibonacci sequence. The ODR for these structures is similar to the ODR of photonic crystals containing left-handed materials. This work would be useful to study the Fibonacci type photonic crystals having graded index materials and also it will open new window to design several photonic crystal devices like sensors, reflectors, etc. in the infrared region.

Omni-directional reflection bands in one-dimensional plasma dielectric photonic crystals

In this paper the omni-directional reflection bands in one-dimensional plasma photonic crystal (PPC) have been studied theoretically. We present the study of plasma photonic crystal, having alternate regions of plasma⿿dielectric (Al2O3 or ZnS). Reflectances from this periodic multilayered structure in TE- and TM-modes are calculated for different angles of incidence in microwave region for omni-directional reflection bands. The reflectance is obtained by solving a Maxwell's equation using a translational matrix method. In addition to this, we have also studied the effect of variation of plasma width as well as plasma density on the reflection properties of plasma dielectric photonic crystal in TE- and TM-modes. The study of reflectance bands of such plasma photonic crystals shows that it can be used as omni-directional reflector.

The modulation on the optical responses of one-dimensional photonic crystals based on the ordered porous TiO2 films

The optical responses of the 1D porous TiO2/SiO2 complete and defect PCs formed with the ordered porous TiO2 film prepared by using the spin coating and annealing techniques have been systematically studied with FDTD simulation technique. The whole photonic band gap can be easily linearly modulated by the structure parameters, such as thickness, porosity, the filled materials, and so on. The defect layer thickness and porosity only modulate the defect state, and have little effects on the whole PBG. It is more important that the 1D porous TiO2/SiO2 complete and defect PCs have no omnidirectional photonic band gap and defect state.

Tunable Multimode and Narrowband in a Photonic Quasicrystal Waveguide

In this work, we propose a photonic quasicrystal waveguide, which contains a hollow core surrounded by coaxial dielectric quasiperiodic multilayer. Due to the self-similarity in the cladding structure, multiple omnidirectional photonic band gaps (PBGs) exist in the waveguide. The light waves with the frequencies within the omnidirectional PBGs are totally reflected, thereafter, the transport of multimodes is achieved in the quasiperiodic waveguide. Further, it is shown that the centre frequency and the width of the omnidirectional PBG can be tuned by the refractive indexes or the generations of the quasiperiodic sequence in the cladding multilayer. As a consequence, both the quality factor and the confinement performance of the waveguide can be significantly enhanced by decreasing the width of the omnidirectional PBGs. The investigations make it possible to design miniaturized multifunctional optical devices, such as on-chip narrowband waveguide-based filters and laser resonators.

Superhydrophobic and Omnidirectional Antireflective Surfaces from Nanostructured Ormosil Colloids

A large-area superhydrophobic and omnidirectional antireflective nanostructured organically modified silica coating has been designed and prepared. The coating mimics the self-cleaning property of superhydrophobic lotus leaves and omnidirectional broad band antireflectivity of moth compound eyes, simultaneously. Water contact and sliding angles of the coating are around 160° and 10°, respectively. Coating improves the transmittance of the glass substrate around 4%, when coated on a single side of a glass, in visible and near-infrared region at normal incidence angles. At oblique incidence angles (up to 60°) improvement in transmission reaches to around 8%. In addition, coatings are mechanically stable against impact of water droplets from considerable heights. We believe that our inexpensive and durable multifunctional coatings are suitable for stepping out of the laboratory to practical outdoor applications.

OMNIDIRECTIONAL REFLECTION EXTENSION IN A ONE-DIMENSIONAL SUPERCONDUCTING-DIELECTRIC BINARY GRADED PHOTONIC CRYSTAL WITH GRADED GEOMETRIC LAYERS THICKNESSES

The omnidirectional re∞ection characteristics of one- dimensional (1D) superconducting-dielectric binary graded photonic crystals (PhCs) are studied by using transfer matrix method. The in∞uences of thickness changing rate, numbers of periods, incident angles are analyzed. And the omnidirectional photonic band gaps are extended markedly in the 1D thickness-graded superconducting- dielectric PhC.

Printed Modified Bow-Tie Dipole Antenna for DVB/WLAN Applications

A printed modified bow-tie dipole antenna which consists of asymmetric-feed and inserted slots is presented to apply to the DVB and WLAN systems. This antenna combines omnidirectional radiation pattern, broad bandwidth, and band rejection in an easy way to fabricate. Experimental results of the constructed prototype indicate that the VSWR 2.5 : 1 bandwidths achieve 166.7%, 28.57%, and 23.63% at 660 MHz, 2450 MHz, and 5500 MHz, respectively.

Analytical investigation of omnidirectional photonic band gaps in one-dimensional superconductor–dielectric photonic crystals

In this paper, the first two total omnidirectional photonic band gaps (OBGs) of one-dimensional (1D) superconductor–dielectric photonic crystals (SDPCs) which composed of dielectric–dielectric and superconductor–dielectric periodic structures have been investigated theoretically by using the transfer matrix method (TMM). Those OBGs originate from Bragg gaps. From the analysis, it is found that this kind of heterostructure has wider frequency ranges of total OBGs for both polarizations in comparison to the dielectric photonic crystals (DPCs) or SDPCs, and the bandwidths of OBGs can be notably enlarged by increasing the thickness of superconductor layer and decreasing the ambient temperature.

Enlarged omnidirectional band gap in one-dimensional plasma photonic crystals with ternary Thue–Morse aperiodic structure

In this paper, an omnidirectional photonic band gap (OBG) which originates from Bragg gap compared to zero-n˜ gap or single negative (negative permittivity or negative permeability) gap, realized by one-dimensional (1D) plasma photonic crystals (PPCs) with ternary Thue–Morse aperiodic structure, which is composed of plasma and two kinds of homogeneous, isotropic dielectric is theoretically studied by the transfer matrix method (TMM) in detail. Such OBG is insensitive to the incident angle and the polarization of electromagnetic wave (EM wave). From the numerical results, the bandwidth and central frequency of OBG can be notably broadened by changing the thickness of plasma and dielectric layers but cease to change with increasing Thue–Morse order. The OBG also can be manipulated by plasma density. However, the plasma collision frequency has no effect on the bandwidth of OBG. These results may provide theoretical instructions to design the future optoelectronic devices based on plasma photonic crystals.

Omnidirectional photonic band gap enlarged by one-dimensional ternary unmagnetized plasma photonic crystals based on a new Fibonacci quasiperiodic structure

In this paper, an omnidirectional photonic band gap realized by one-dimensional ternary unmagnetized plasma photonic crystals based on a new Fibonacci quasiperiodic structure, which is composed of homogeneous unmagnetized plasma and two kinds of isotropic dielectric, is theoretically studied by the transfer matrix method. It has been shown that such an omnidirectional photonic band gap originates from Bragg gap in contrast to zero-n¯ gap or single negative (negative permittivity or negative permeability) gap, and it is insensitive to the incidence angle and the polarization of electromagnetic wave. From the numerical results, the frequency range and central frequency of omnidirectional photonic band gap can be tuned by the thickness and density of the plasma but cease to change with increasing Fibonacci order. The bandwidth of omnidirectional photonic band gap can be notably enlarged. Moreover, the plasma collision frequency has no effect on the bandwidth of omnidirectional photonic band gap. It is shown that such new structure Fibonacci quasiperiodic one-dimensional ternary plasma photonic crystals have a superior feature in the enhancement of frequency range of omnidirectional photonic band gap compared with the conventional ternary and conventional Fibonacci quasiperiodic ternary plasma photonic crystals.