Tunable Defect Mode Research Articles

Tunable polarization-dependent defect modes and lateral shifts of one-dimensional photonic crystals containing Dirac semimetal-based hyperbolic metamaterials and chiral materials

The transmission and lateral shift properties of the one-dimensional photonic crystals containing Dirac semimetal-based hyperbolic metamaterials and chiral material defects are theoretically investigated by using the transfer matrix method in terahertz. It is found that the angle-independent omnidirectional photonic bandgaps (PBGs) for p-polarization can be realized in the photonic crystals made of dielectric and the Dirac semimetal-based hyperbolic metamaterials. However, the PBGs are blue-shifted with the incident angle for s-polarized wave. The omnidirectional PBGs can be tunable with the Fermi energy of the Dirac semimetal, the thickness ratio of the constitute layers and the structural parameters. When one or two isotropic chiral material layers are introduced in the photonic crystals, double or four polarization-dependent defect modes are found in the bandgap under oblique incidence due to the coupling and conversion between different polarized waves in the chiral defects. The frequency interval of the defect modes changes with the chirality parameter and the incident angle. It is also found that when a light is incident on the defective photonic crystals, the giant positive and negative Goos-Hänchen shifts of co-polarization reflected waves can be induced around the defect modes, which are sensitive to the polarization, the incident angle, the incident frequency and the chirality. The special optical properties of the proposed defective multiplayers provide possibilities for practical applications in designing polarization sensitive optical devices, such as filter and sensor.

Localized defect modes’ tunability by Octonacci photonic bandgap structures with thin high-Tc superconductors

The reflectance spectrum, through 1D superconducting photonic bandgap structures organized following the Octonacci sequence, is studied by employing a theoretical calculation based on the transfer-matrix method and the two-fluid Gorter–Casimir theory. The proposed hetero-structures are made up of Yttrium oxide (A) and YBa2Cu3O7 (B) materials. We report the localization of modes for specific generations of the Octonacci sequence and TEM mode. We discuss the field-localization properties for different Octonacci sequences. It is noticed that localized defect modes of intensity scale up to 99% are sensitive to the wave-incident-angle and the TEM wave polarizations. The lateral position of the localized defect mode can be notably adjusted by the operating superconductor’s temperature (T), by applying a structural strain along the stacks, and by specific thicknesses of the used superconductor. The spectra exhibit forbidden wavelength zones around the localized defect modes in which the bandwidths increase with the strain coefficient h and under critical superconductor temperatures. The given structure has potential applications in tunable localized defect modes and is very useful in optical resonators.

Tunable defect modes through the (YBCO-Yttria) based on Octonacci photonic quasicrystals

The transmission spectra by a one-dimensional (1D) inhomogeneous stratified medias organized following the Octonacci sequence are investigated. The transfer-matrix method and the Frequency-dependent dispersion formula according to the two-fluid Gorter–Casimir theory are deployed. The proposed hetero-structures are made up of Yttrium oxide, known as yttria,Y2O3 (A) and superconductor (B): yttrium–barium–copper oxide (YBa2Cu3O7), resulting in the (BTO/Y2O3)N/YBCO/(Y2O3/BTO)N multilayered nanostructure array. We report the localization of modes through the multilayered stacks built accordingto the inflation rule of quasi-periodic Octonacci sequence. Localized defect modes were obtained for specific generation of Octonacci structure and for both TE and TM modes. The optical properties exhibiting different regions with zero transmission called photonic bandgaps (PBGs) that can be tuned by Octonacci order and temperature of Bulk superconductor. The performance of defect modes that allows the propagation of optical signals and the inter-channels are evaluated by tailoring the superconductor temperature, the Octonacci order, the direction of the incident wave, and the deformation degree (parameter that control the thickness of superconductor lattices). The proposed system exhibits similar localized resonators operating at cryogenic temperature environments. We verify that bandgaps modifications are influenced by the deformation strain applied along whole thicknesses slab.

Employing the Defective Photonic Crystal Composed of Nanocomposite Superconducting Material in Detection of Cancerous Brain Tumors Biosensor: Computational Study

The present research is focused on the externally tunable defect mode properties of a one dimensional (1D) defective photonic crystal (DPhC) for fast detection of cancerous brain tumors. The proposed design has utilized conventional 1D DPhC whose cavity is coated with SiO2 nanoparticles embedded in a superconducting material layer called a nanocomposite layer. The purpose of a nanocomposite superconducting layer is to induce temperature dependent external tuning of the defect mode inside PBG, in addition, to changing in the angle of incidence. The inclusion of a nanocomposite layer also improves the interaction between light and different brain tissue samples under examination. In order to investigate the transmission properties of the proposed structure the transfer matrix formulation in addition to the MATLAB computational tool has been used. First, we have chosen the optimized internal parameters at normal incidence to obtain the maximum performance of the design. Secondly, the effect of change in angle of incidence has been studied to further increase the performance by means of sensitivity, quality factor, the figure of merit and limit of detection to ensure external tuning of defect mode. After achieving a maximum value of sensitivity (4139.24 nm/RIU) corresponding to a sample containing a wall of brain tissues at θ = 63° we have further investigated the effect of change in temperature of nanocomposite layers on the position and intensity both of the defect mode inside PBG. We have found that the increase in temperature results in minute changes in sensitivity but a significant increase in the intensity of defect mode which is highly required in any photonic biosensing design. The findings of this study may be very useful for designing various bio-sensing structures which could have a significant and decisive role in the field of biomedical applications.

Theoretical Study of Tunable Optical Resonators in Periodic and Quasiperiodic One-Dimensional Photonic Structures Incorporating a Nematic Liquid Crystal

In this work, the transfer matrix method (TMM) is employed to investigate the optical properties of one-dimensional periodic and quasiperiodic photonic crystals containing nematic liquid crystal (NLC) layers. This structure is expressed as (ABC)J(CBA)J and made of alternated layers of isotropic dielectrics SiO2 (A), BGO (B) and nematic liquid crystal (C). The simulation study shows that the proposed ternary configuration exhibits tunable defect mode within the photonic band gap (PBG) that can be manipulated by adjusting the thicknesses of NLC layers in order of the periodic lattice. In addition, the optimized structure permits for strong confinement light giving rise to an optical microcavity. The application of an applied voltage into NLC layers enables improving the sensitivity by guiding the local defect mode. It has been also shown that by applying quasiperiodic inflation according to Rudin Shapiro Sequence (RSS) scheme to main periodic structure, several tunable resonant modes appear within the PBG. The presence of such sharp resonant peaks reflects that the quasiperiodic NLC-based structure behaves like multiple microcavites with strong light-matter coupling.

Optical axis -sensitive intensity transmission of the optical filters based on anisotropic electro optical photonic structures

This present work reports on a study regarding the adjusting intensity transmission optical filters in one-dimensional photonic crystals (1DPCs) with an anisotropic electro optical material (AEO) defect layer. The transmission properties of the proposed PCs in the visible wavelength areas are collected by using the 4 × 4 transfer matrix method. The results show that by embedding the anisotropic layer as a defect, the intensity transmission of optical filters can be affected by alteration of the optical axis of anisotropic layer in the presence of a perpendicular bias voltage. Therefore, due to optical axis dependence of the anisotropic layer, the designed structurer can be used as a novel polarizer, in which the intensity transmission of the optical filter can be controlled and maintaining the working wavelength unchanged. Also, the influence of the variation the incidence angle at the P and S polarization on the tunability transmittance properties are theoretically investigated We can have tunable defect modes, leading to developing a new perspective in the design of new optical devices.

Thermally tunable terahertz omnidirectional photonic bandgap and defect mode in 1D photonic crystals containing moderately doped semiconductor

A new one-dimensional photonic crystal (1DPC) containing moderately doped silicon (m-Si) semiconductor is proposed and its tunable properties are theoretically investigated. The tunable complex permittivity of m-Si with temperature is the central idea that makes the 1DPC thermally tunable. The 1DPC systems such as (m-Si/SiO2)12 and defective (m-Si/SiO2)6D(m-Si/SiO2)6 are examined in the spectral range of 0.4–0.8 THz with varying temperature from 40 to 100 K. Air and m-Si are considered as defect layer (D) in two different 1DPC systems. Our simulation shows that the photonic band gap (PBG) shifts to higher frequency and the omnidirectional PBG gets narrower with increasing temperature. The defect mode in both defective 1DPCs shifts to higher frequency with increasing temperature. The temperature sensitivity of peak transmission is found better in the air defective 1DPC, while that of defect frequency is better in the m-Si defective 1DPC. The angle of incidence and polarization dependency of the defect modes are studied in detail. The present work can be utilized for the development of tunable omnidirectional mirrors and narrow bandpass filters in the terahertz region as well as THz light based thermal sensors.

Numerical analysis of tunable defect mode in cylindrical photonic crystals configuration

AbstractIn contrast to most of the previous publications that has addressed the dependency of the defect mode on temperature in planner one‐dimensional photonic crystal, we study this dependency in cylindrical photonic crystal taking into consideration both thermal‐optical and thermal expansion effects. Our analysis, based on the cylindrical transfer matrix, is conducted for both types of polarized electric and magnetic waves. Our structure is composed of arrays of cylindrical coaxial shells of TiO2 and Al2O3 with single defect layer. Numerical results show that the defect mode's wavelength can be effectively tuned, following a linear relation, by changing the temperature for both types of polarized waves. In addition, the peak transmittance is dependent on the number of periods and the starting inner radius. Moreover, decreasing the inner radius is associated with separation between the two polarizations.

Tunable defect modes of one-dimensional photonic crystals containing a Dirac semimetal-based metamaterial defect layer.

The transmission properties of one-dimensional photonic crystals (PCs) containing a metamaterial (MM) defect layer are investigated using the transfer matrix method. The MM is composed of alternating layers of a dielectric material and a Dirac semimetal (DS) material. Numerical results show that the defective PCs possess a tunable defect mode, which is significantly dependent on the Fermi level of the DS as well as the structural parameters of the MM defect layer. The defect mode properties under different incident angles for TE and TM polarizations are also studied. Such defective structures have potential applications in tunable filters and sensors in terahertz regions.

Tunable Bragg defect mode in one-dimensional photonic crystal containing a graphene-embedded defect layer.

Using the transfer matrix method, the transmission properties of defective one-dimensional photonic crystal are analyzed in the terahertz region. The defect layer is composed of a graphene-embedded dielectric layer. We investigate the variation of the defect mode's frequency as a function of graphene chemical potential for different values of incident angles. The numerical results show that the frequency of the defect mode can be tuned effectively as the chemical potential of graphene nanolayers changes using an applied gate voltage. The present results can be useful in designing tunable graphene-based photonic devices such as filters and sensors in terahertz regions.

A magnetically tunable non-Bragg defect mode in a corrugated waveguide filled with liquid crystals

A magnetically tunable, non-Bragg defect mode (NBDM) was created in the terahertz frequency range by inserting a defect in the middle of a periodically corrugated waveguide filled with liquid crystals (LCs). In the periodic waveguide, non-Bragg gaps beyond the Bragg ones, which appear in the transmission spectra, are created by different transverse mode resonances. The transmission spectra of the waveguide containing a defect showed that a defect mode was present inside the non-Bragg gap. The NBDM has quite different features compared to the Bragg defect mode, which includes more complex, high-order guided wave modes. In our study, we filled the corrugated waveguide with LCs to realize the tunability of the NBDM. The simulated results showed that the NBDM in a corrugated waveguide filled with LCs can be used in filters, sensors, switches, and other terahertz integrated devices.

Tunable defect mode in a soft wrinkled bilayer system

Here we study the defect mode in a wrinkled soft bilayer induced by a local geometrical defect introduced into the system. We show that the band gap of the studied composite system depends on the wrinkling-induced stress pattern and is not sensitive to the compression strain ε in the given loading range. However, the frequency of the defect mode apparently varies with ε. This interesting phenomenon enables us to widely tune the spatial extension of the defect mode from highly localized to completely extended by simply controlling the imposed external load. Our strategy to create a tunable defect mode in a soft layered composite is simple and straightforward and may find such broad applications as the development of advanced soft metamaterials and corresponding devices.

Electrically Controlled Reflection Band and Tunable Defect Modes in One-Dimensional Photonic Crystal by Using Potassium Titanyl Phosphate (KTP) Crystal

Electrically Controlled Reflection Band and Tunable Defect Modes in One-Dimensional Photonic Crystal by Using Potassium Titanyl Phosphate (KTP) Crystal

Tunable photonic defect modes in one-dimensional photonic crystals containing exponentially and linearly graded index defect

We present an analytical study of the defect modes in one-dimensional (1-D) photonic crystals with defect layer of exponentially and linearly graded index materials. The relative refractive index in the defect layer varies continuously along the direction perpendicular to the surface of layer. The transmission spectra demonstrate that there exist two defect modes inside the photonic band gap for the quarter-wave layers stacking photonic crystal structures with a defect layer of graded index material. The grading profiles of the defect layer affect the frequency and intensity of photonic defect modes. The intensity, frequency and number of defect modes have been changed with the thickness and gradation parameter of graded index defect layer. Moreover, results show that different incident angle in TE and TM polarizations can also be changed the frequency and intensity of the defect modes remarkably. This defect mode splitting and tuning phenomenon in 1-D photonic crystals containing defects of graded index materials can be used to design filters, sensors, and other photonic devices.

Tunable defect mode realized by graphene-based photonic crystal

In this literature, we propose an active terahertz 1D photonic crystal, which consists of silicon layers and air layers. A graphene sheet is embedded at the interface between dielectric and air. Tunable photonic band gap is realized by changing the Fermi level of graphene. Transmission Matrix Method is utilized to explain the influence of the graphene layer. We also demonstrate that a dielectric slab attached with a thin sheet made of single-negative metamaterial acts like a pure dielectric slab with a thinner thickness. A tunable blue shift of the band gap can be realized by simply applying different chemical potentials on the graphene sheet. This feature can be utilized for the design of tunable high-gain antenna array and force generator in terahertz band.

Experimental realization of tunable defect mode in photonic crystal

Defect modes located at different position were prepared by introducing defect layers in the porous alumina based photonic crystals. Furthermore, experiments and simulations were carried out to investigate the properties of such defect modes. The results show that defect mode can be tuned easily by changing thickness and location of the defect layer, moreover, the optical properties of defect mode when changing the incident angle are also studied.

Tunable plasmonic band gap and defect mode in one-dimensional photonic crystal covered with graphene

We study the transmission characteristics of surface plasmons at the interface of a one-dimensional photonic crystal (1DPC) and a monolayer graphene sheet. The composite structure with a plasmonic band gap (PGB) was obtained by covering a graphene sheet on the lateral side of the 1DPC. Defect modes in these structures appeared when defect layers were inserted in the 1DPC. On the condition that the chemical potential of graphene is much larger than , the PBG and defect mode shift to higher frequencies as the chemical potential increases. As the carrier density in graphene can be controlled by the gate voltage, both the PBG and defect mode can be easily tuned by the chemical potential, which is determined by the carrier density.

Localized electromagnetic modes in one-dimensional defective fractal multilayers containing ε-negative and μ-negative metamaterial layers

Tunable defect modes in one-dimensional fractal structures containing ε-negative metamaterials (ENG) and μ-negative metamaterials (MNG) are analyzed with transfer matrix method. By inserting double-positive (DPS) type defect layers in the supposed structure, ENG–DPS–ENG and MNG–DPS–MNG arrangements are considered. It is found that in the ENG–DPS–ENG (MNG–DPS–MNG) arrangement for TE polarization defect modes are sensitive (insensitive) to incident angle while for TM polarization they are invariant (variant). Also, the spectral position of the defect mode is invariant upon the change of scale length. Furthermore, by varying defect layers thicknesses, defect modes shift to the lower frequencies.

Fast-tunable terahertz wave filter based on Kerr medium

Abstract We numerically demonstrate terahertz filter with independently tunable defect mode based on a nonlinear polymer photonic crystal made of polystyrene doped with coumarin. The central frequency of the filtering channel continuously shifts with the increase of pump intensity. The simulated results theoretically provide the principle for fabricating independently tunable terahertz filter by utilizing one-dimensional photonic crystals with defects. The center wavelength shifts about 0.012 mm under the excitation of 25 MW/cm 2 pump laser. When manufacturing tolerances varies from 0% to 20%, the quality factor of terahertz wave channel changes from over 7600 to less than 4700. Time response of the terahertz wave filter is in the order of several picoseconds.

Tunable defect mode in a semiconductor-dielectric photonic crystal containing extrinsic semiconductor defect

In this work, we theoretically investigate the tunable properties in the defect mode for a defective semiconductor-dielectric photonic crystal (SDPC). Here, the defect layer is an extrinsic semiconductor of n type InSb, n-InSb, which has a strong temperature- and concentration-dependent dielectric constant. With the use of n-InSb, the defect mode can be tuned as a function of temperature and concentration. The defect mode frequency is blue-shifted as the concentration or the temperature increases. In addition, this defect mode frequency shows a nearly linear dependence on the concentration but a nonlinear dependence on the temperature. Finally, by increasing the defect thickness leads to the presence of multiple defect modes which can be used to design a multichanneled filter.