Position Of Defect Mode Research Articles

Ultra-high sensitive cancerous cells detection and sensing capabilities of photonic biosensor

The ultra-high sensitive cancer cell detection capabilities of one-dimensional photonic crystal with defect have been theoretically examined in this work. The simulations of the work have been carried out with MATLAB programming and transfer matrix method. The performance of the proposed biosensor loaded separately with samples containing different cancer cells has been studied by changing the period number, defect layer thickness, and incident angle corresponding to s polarized light only to identify the parameters under which the proposed design becomes ultra-sensitive. The working principle of the proposed biosensor is to sense the minute change in the refractive index of the analytes containing different cancer cells of human. This sensing is done shifting the respective defect mode inside photonic band gap of the structure from one position to other near by position due to change in the refractive index of sample under consideration. Our structure under optimum conditions yields maximum shifting in the position of defect mode from 1538 to 1648 nm corresponding to the samples containing normal and Glioblastoma cells of refractive indices 1.350 and 1.4470 respectively which results a ultra-high sensitivity of 4270.525928 nm/RIU.

Analysis of a gas sensor based on one-dimensional photonic crystal structure with a designed defect cavity

A symmetric one-dimensional photonic crystal configuration with defect layer is proposed for an optical gas sensor based device application. Here, Silicon and Si3N4 are considered as materials of dielectric layers with zero value of extinction coefficient in the wavelength range of concern. The transmission of PC configuration is estimated using the transfer matrix approach in case of configuration with and without defect, and the infiltrated gas is treated as defect layer. On the basis of the defect mode’s wavelength, gas can be determined. In addition, quality factor and sensitivity of the device are improved due to the variation of refractive index of layer B, thickness of defect, angle of incidence and the number of unit cells on either side of defect layer. By making analysis of the effect of these parameters on the sensitivity and quality factor, interesting results have been obtained and conclusions drawn. We have also proposed and investigated a symmetric structure with defect made with a single material to improve optical sensing parameters. Further for the sake of comparison, the various gases are used to show improved sensing characteristics for respective gases, which can be used to determine gas. It is inferred that such refractive index optical sensor based on defect mode position is highly sensitive and offers precise optical sensing characteristics and possibly find applications in gas detection.

The Transmission Properties of One-Dimensional Photonic Crystals with Gradient Materials.

In this paper, we studied the transmission properties, including photonic band gap (PBG) and defect mode properties, of one-dimensional photonic crystals (1D PCs) consisting of gradient materials. When keeping the average refractive index of the gradient materials in the 1D gradient-material PCs (1D GPCs) the same as the index of the corresponding normal materials in the 1D normal-material PCs (1D NPCs), by transfer matrix method, we found that the complete 1D GPCs with high-index gradient materials benefit to achieve larger omni-PBG than that in 1D NPCs. In our high-index gradient material case, for TE(TM) wave, the optimal omni-PBGs in 1D GPCs with first- and second-order gradient materials are 38.6% (50.2%) and 15.9% (22.3%) larger than that in 1D NPCs; while for the optimal relative bandwidths of omni-PBG, the corresponding promotions are 41.1% (52.3%) and 16.1% (22.6%), respectively. In addition, when defective 1D GPCs have gradient-material defect, the position of defect modes can be adjusted by selecting proper parameters of the gradient materials. These types of research are useful for designing wide PBG devices and tunable narrow-band filters which have potential application in optical communication.

Electric field distribution of photonic crystals waveguide with function line defect

In this work, the finite element and supercell methods are used to study the effect of function line defect on the photonic band structure and electric field distribution in a two-dimensional photonic crystals waveguide. We designed to introduce a row of function defect in the photonic crystals waveguide. The transmission characteristics of the photonic crystals waveguides are modulated by adjusting the function coefficient k and parameter b of the dielectric constant of the function defect dielectric column. By changing the structure parameters of the dielectric constant, the radius of the function defect dielectric column and the dielectric constant of the two-dimensional regular photonic crystals dielectric column material, we found that the band gap position, band gap width, defect mode number, defect mode position and defect mode width change. The electric field is well localized at the defect location, but their intensity are different. The three-pole defect mode can be activated, and the defective mode eigenfield distribution is symmetrical. Compared with the two-dimensional regular photonic crystals waveguide, the width of forbidden band becomes wider and the number of defect modes increases. The band gap structure and electric field distribution have the adjustability for the two-dimensional photonic crystals waveguide with function line defect. These results will provide new designed methods and theoretical basis for the related optical devices.

Numerical characterization of 1D-Photonic crystal waveguide for female reproductive hormones sensing applications

The current work investigates the detection of a wide range of estradiol and progesterone hormone concentrations by the use of a defective 1D photonic crystal. The suggested structure consists of repeating layers of PbS and SiO2, with a central cavity layer. The transfer matrix technique is manipulated to examine the transmission spectrum of the proposed structure. The mainstay of the present work is to analyse the shift in the wavelength of the defect mode concerning the changes in different concentrations of hormones that are infiltrated into the cavity layer. In the course of a simulation, various geometrical parameters such as the thickness of the cavity layer and incident angle are properly optimized to envisage high performance. The colour map plot is investigated to convey a clear view of the shift of defect mode position concerning the change in incident angle. Moreover, all the sensing parameters like sensitivity, figure of merit, quality factor, signal-to-noise ratio, sensor resolution, and limit of detection are evaluated for each hormone at different incident angles. The main application behind this study is that it is important to sense the levels of estradiol and progesterone hormones for balanced needs in a women's reproductive system as well as to monitor the overall health systems. This proposed structure is suitable for bio-sensing applications due to their cost-effective fabrication and high performance.

Design and Performance Analysis of Reconfigurable 1D Photonic Crystal Biosensor Employing Ge₂Sb₂Te₅ (GST) for Detection of Women Reproductive Hormones.

The present research demonstrates a novel 1D photonic crystal (PhC) based reconfigurable biosensor pertaining to label-free detection of different concentrations of progesterone and estradiol, which play a vital role in developing reproductive hormones in women. The proposed sensor is designed by an alternative arrangement of Na3 AlF6 and CeO2, with a central defect layer. A thin layer of novel phase change chalcogenide material (Ge2 Sb2 Te5) is deposited along the two sides of the defect layer to improve the sensing performance. Numerical simulation of transmission spectrum for TE mode is carried out by using the transfer matrix method (TMM). The mainstay of this research is centered on the assay of shift in the defect mode position and intensity with respect to different concentrations of analyte, by changing the phase of the GST material from amorphous to crystalline. Interestingly, we observed a high tunability in defect mode wavelength, when the phase is changed from amorphous to crystalline, which leads to accomplishment of a high sensitivity of 1.75 nm/nmol/L for progesterone and 20.5 nm/nmol/L for estradiol. Aside from sensitivity, other significant parameters like figure of merit and detection limit are computed, which give a deep insight into the sensing performance. These encouraging sensing performances pave the path for efficient detection of different concentrations of progesterone and estradiol to monitor various gynecological problems in women.

Optical properties of one-dimensional plasma photonic crystals with inhomogeneous plasma density distribution functions.

This paper investigates the optical properties of the two plasma photonic crystal structures. The first structure contains periodic thin layers of plasma with heterogeneous densities, and in the second one, the heterogeneous plasma layer has been applied as the defect layer of a one-dimensional photonic crystal. Herein, the plasma density distribution function is considered a continuous function of plasma critical density as follows: n=ncrf(r→), where ncr=meε0ω2/e2 represents the critical density of the plasma and f(r→) indicates the plasma density distribution function. The heterogeneous plasma layer is assumed to be composed of several homogeneous sublayers with constant density. The transfer-matrix method is applied in calculations, and the total transfer matrix is obtained by multiplying the transfer matrices of each sublayer. Properties and behavior of the photonic bandgap and the defect mode for five different plasma density distribution functions and applied external constant magnetic field are comparatively investigated. Results show that, in the first structure, increasing the incident angle from 0° to 30° causes a bandgap shift to higher frequencies. So, the incident angle is a parameter that can control the bandgap. In the defective structure, the intensity of the defect modes is almost the same in all five distributions, but their locations in the spectrum are different. The effect of the lateral position of the maximum density and external constant magnetic field on the defect mode position is also investigated. The capability of controlling the photonic bandgaps and defect modes of the plasma photonic crystals creates wide applications in promising tunable optical devices, such as optical filters.

Enhancement of transmission in 1D thermal tunable metallic photonic crystal filter with exponential gradation thickness

Using the transfer matrix method, the transmission of 1D thermal tunable metallic photonic crystal (PC) filter with symmetry exponential gradation of thickness has been examined in this article. For the purpose of making this structure, three different materials silicon, silica, and silver have been used. The refractive index of silver is considered as a function of temperature and wavelength. The dependence of the silicon refractive index on the wavelength is also considered in calculations. The effect of the variation of temperature and incident angle on the transmission peaks has been investigated. By increasing the temperature, the transmission peaks in the position of defect modes move toward the larger wavelength at a given incident angle. When the incident angle is increased, however, they shift toward the shorter wavelength in both polarizations. The height of transmission peaks decreases linearly by increasing the temperature. Results are compared with those obtained in our previous work. The position of the transmission peaks in the structure with the exponential gradation of thickness is higher than the non-graded and linear graded, and the transmission peaks are sharper in TE polarization.

The point defect and eigenfield distribution for two-dimensional function photonic crystal

With the plane wave expansion method, we introduced the concept and theory of two-dimensional function photonic crystal, and compared the theoretical difference of two-dimensional function photonic crystal with the conventional photonic crystal. In Numerical calculation, with COMSOL software based on finite element method, we have studied the bandgap structure, defect mode and eigenfield distribution for the two-dimensional function photonic crystal with and without point defect. For the two-dimensional function photonic crystal, the dielectric constant of dielectric column is the space coordinate function, which can be realized by the electro-optic effect and the Kerr effect. In the paper, we studied the dielectric constant function form is [Formula: see text](r) = kr + b, and the parameters k and b can be adjusted by changing the electric field or light intensity applied to the dielectric column. By changing the parameters k or b of the dielectric column dielectric constant, we found the two-dimensional function photonic crystal transmission characteristics have the adjustability, i.e., the bandgap structure, the bandgap position and width, the defect mode position, width and number and the defect mode eigenfield distribution can be changed by adjusting the parameters k or b, which can be used to conveniently design the bandgap structure that we need. These conclusions will provide important theoretical basis and methods for optical devices design.

One-dimensional phononic crystals that incorporate a defective piezoelectric/piezomagnetic as a new sensor

In this paper, we have studied the propagation and localization of acoustic waves in a one-dimensional (1D) phononic crystal at the effects of both electric and magnetic fields. We focused on the sensing and measuring the electric and magnetic fields by adjusting the position of the transmitted peak (defect mode) inside the two piezoelectric/piezomagnetic defect layers (0.7 PMN-0.3PT/Terfenol-D). The defect mode is shifted towards the lower frequencies by applying electric and magnetic fields and towards the higher frequencies by opposing the field’s direction. The bigger the value of the applied field is the greater movement in the peak position is. In addition, our results revealed that the magnetic field has a bigger influence than the electric field on the position of the defect mode. Moreover, we studied such movement of the defect mode position by applying the electric and magnetic field simultaneously. These results can be used to improve and enhance piezoelectric and piezomagnetic energy harvesters.

Filtering properties of Thue–Morse nano-photonic crystals containing high-temperature superconductor

In this paper, we introduced new design of quasi-periodic layered structures by choosing order two of ternary Thue–Morse structure. We considered Superconductor-dielectric photonic crystal with mirror symmetric as (ABSSAB)N(BASSBA)N composed of two kinds of nano-scale dielectric layers (A and B) and high-temperature superconductor layers where N is the number of period. This structure is assumed to be the free space. By using the transfer matrix method and the two fluid model, we theoretically study the transmission spectrum of ternary Thue–Morse superconducting photonic crystals with mirror symmetry and introduce this structure as a narrow optical filter. We showed that transmission peak so-called defect mode appears itself inside the transmission spectrum of suggested structure as same as defective layered structure. Also, we analyzed the influence of various related parameters such as the operating temperature of superconductor layer on position of defect mode. The redshift of defect mode with increasing the operating temperature was observed.

Defect Modes Control in Coupled Magnonic Crystals

We report on the theoretical study of magnetostatic surface wave propagation through the two side-coupled 1-D magnonic crystals (MCs) with broken translational symmetry. Using the transfer matrix method, we obtained transmission and reflection coefficients. Existence of two defect modes in such four-port planar structure was shown. We consider the possibility of controlling the position of defect modes by changing coupling between MCs. Comparison between investigated structure with coupled defect-free magnonic crystals was provided.

Electro-optical tenability properties of defective one-dimensional photonic crystal

In this work, the optical transfer matrix formalism was applied to study the linear electro-optic effect on perfect and defective one-dimensional photonic crystal (1D-PC) composed of lithium niobate and polymer (polystyrene) multilayers. The effects of an external electrical field on the reflectance spectra of the proposed PCs were studied as a function of the angle of incidence and the types of polarization (TE and TM waves). The results show that, at a constant angle of the incident, the PBGs are shifted to shorter wavelengths for both TE and TM waves as the applied electric field increased. The position of defect mode decreases linearly from 1.401 to 1.379μm for TM wave and from 1.398 to 1.377μm for TE wave as the applied electric field increased from 0 to 100v/μm at an angle of incident 50°. By increasing the angle of the incident from 0 to 50° at constant applied electric field, the position of PBG for both TE and TM are shifted toward the shorter wavelengths. In addition, the width of the PBGs of TE wave is increased from 0.334 to 0.358μm and the width of the PBGs of TM wave is decreased from 0.334 to 0.248μm at 100v/μm. This study may be valuable for designing tunable photonic devices with driving electrical field, which has potential applications in the area of photonics and optoelectronics.

The defect mode in a low-dimensional waveguide microwave photonic crystal

It is shown that the violation of periodicity in a low-dimensional waveguide microwave photonic crystal, in which the periodic structure is formed by dielectric layers and adjacent metal plates partly overlapping the waveguide cross section and forming capacitive gaps between the plate edge and wide wall of the waveguide, leads to the appearance of a defect (impurity) mode. It is established that the defect mode position on the frequency scale significantly depends on both the thickness of “disturbed” dielectric layer and the capacitive gap width of diaphragms.

Defect mode in one-dimensional photonic crystal consisting of single-negative materials with an impurity layer

The transport properties of one-dimensional photonic crystal consisting of single-negative materials, with an impurity layer, are studied by using the transfer matrix method. The results show that the defect mode appears in the forbidden band of the photonic crystal when there is a defect layer. The position of defect mode moves from the high frequency of the forbidden band to the low frequency with permeability μ increasing. And the position of defect mode moves from the low frequency of the forbidden band to the high frequency with permittivity ε increasing. These characteristics can be used to dynamically control the optical transmission.

Low-threshold bistability in nonlinear microring tower resonator

Microring tower resonators, which are a chain of microring resonators stacked on top of each other, are of great interest for nonlinear optics due to their unique features such as very high compactness, coupling efficiency and quality factor. In this research, we investigate the optical bistability in microring tower (MRT) with Kerr nonlinearity by using the coupled mode theory, and demonstrate how a proper defect into the structure can lead to low threshold bistability. In particular, we observed optical bistability in nonlinear defect modes with switching power as low as 165 μW through numerical calculations in a structure with a overall loss on the order of 0.01 mm. In addition, we also develop an analytical model that excellently gives the position of defect modes in linear regime.

Influence of defect mode displacement in photonic crystal band gap over light group velocity

The light group velocity of defect mode in photonic crystal is active controlled in order to gain controllable light delay by using thermo-optic effect to change the reflective index of material or changing the geometry structure of photonic crystal. From former research we know that the position of defect mode in band gap is changed with light group velocity. Our research further finds that the position of defect mode can be kept by changing more than one parameter correspondingly, and meanwhile the group velocity is not changed too. It comes to the relationship between position of defect mode in photonic band gap and light group velocity, and it is proved theoretically using the principle of plane wave expand method.

Electrooptical Switching in a One-Dimensional Photonic Crystal

An electrooptical narrow-band switch within wide spectral range on the base of photonic crystal/liquid crystal cell has been designed. The cell consists of thin layer of a planar oriented nematic which is confined by two identical multilayer dielectric mirrors. Presence of defect layer in the center of periodic structure induces the origin of the spectral windows (defect modes) inside the photonic crystal bandgap of the transmission spectrum. The transmittance of the cell placed between crossed polarizers depends on the matching of wavelengths for the defect modes of two polarizations and their relative phase retardation. In turn the spectral position of defect modes and the phase retardation were controlled by applied voltage that may result both in the addition and diminution of the defect modes intensities.

Properties of omnidirectional gap and defect mode of one-dimensional photonic crystal containing indefinite metamaterials with a hyperbolic dispersion

The structure of one-dimensional photonic crystal (1DPC) containing indefinite metamaterials with a hyperbolic dispersion relation is proposed to realize the omnidirectional gap for the design of omnidirectional reflectors and filters. It is demonstrated that this 1DPC can result in a similar zero average index (zero-n¯) gap usually appearing in the 1DPC containing isotropic left-handed materials. The properties of zero-n¯ gap and defect modes of this photonic crystal are studied in detail. The edge of this zero-n¯ gap is insensitive to incident angle and polarization of light in contrast to the Bragg gap. When a defect layer is introduced into the 1DPC, a defect mode appears inside the omnidirectional gap. The spectral position of defect mode is found to be weakly dependent on the incident angle of light and nearly invariant to the scale length of photonic crystal.

Optimization of two-photon absorption enhancement in one-dimensional photonic crystals with defect states

One-dimensional photonic crystals with a defect layer of CdS were fabricated. The observed enhancement of two-photon absorption (TPA) in the CdS layer can be attributed to the intensified optical field confined within the defect layer of the photonic crystal. The results show that the enhancement of TPA coefficient depends basically on the number of periods of the photonic crystal and the defect mode position in the photonic band gap. The observation agrees qualitatively with the expectations of a computation by matrix transfer formulation.