Defect Rods Research Articles

Amperometry sensor for real time detection of hydrogen peroxide adulteration in food samples

Porous and defective nanomaterials lead to higher adsorption and are widely used in electrochemical sensor applications. The rGO-MoS2 tailored defect rod shapes provide rapid electron conduction thanks to redox reactions in the sensing medium. Modified polyethylene terephthalate (PET) flexible carbon screen-printed electrode (SPE) shows H2O2 sensing in food samples. We measured linear current amperometry signals in various sensing mediums of 0.1 M phosphate buffer solution (PBS), raw apple juice, and raw milk in the 1 to 50 μM range. Synergistic effects improved the sensing performance by sensitivity (S) of ∼ 773.33 μA/cm2 μM and limit of detection (LOD) of 0.017 μM (S/N, 3:1) in 0.1 M PBS. The observed LODs in the juice and milk samples are 0.025 μM (S = 324.33 μA/cm2 μM) and 0.046 μM (S = 138 μA/cm2 μM), respectively. This non-enzymatic research is fit to employ H2O2 sensing, implementing handheld, real-time controlled units in liquid food samples.

Design and simulation of high-quality factor all-optical demultiplexers based on a two-dimensional photonic crystal

The present study proposes a new type of wavelength division multiplexing as an optical demultiplexer with four, eight, and sixteen output channels. The proposed structure consists of a two-dimensional square array of dielectric rods. The wavelength selection is performed by two defect rods and one defect with a rectangular cross-section. The values of the parameters related to each defect are selected so that the resonant wavelength associated with each output channel is located in the third telecommunication window (1.55μm). It is observed that the proposed demultiplexers demonstrate a high transmission efficiency and low crosstalk. As it is wanted to see just one sharp wavelength at the output of each channel, the quality factor needs to be maximized. Based on the results, the maximum values for demultiplexers with four, eight, and sixteen channels are 19863.89, 14264.57, and 32304.46, respectively. Due to the device’s small size, it can be used for wavelength division multiplexing (WDM) systems in photonic integrated circuits.

Design of an ultra-compact and high-contrast ratio all-optical NOR gate

In this research, an all-optical NOR gate is designed and simulated based on two-dimensional photonic crystals. A square lattice has been used to design this structure. This logic gate has two main inputs, a bias input, and an output. Because the output of the NOR gate must be “1” for zero inputs, a bias input is required. One of the characteristics of this structure is its small size for use in optical integrated circuits. Also, in order to reduce the detection error in the output, it has been tried that the outputs have a suitable difference in two “0” and “1” logical states. The use of a small number and simple point defects makes the design of this gate easier. The simulation results show that the proposed structure is suitable for working at a wavelength of 1.55 µm. Also, the amount of optical power at the output is high in the “1” logical mode and low in the “0” logical mode. In the proposed gate, the normalized output power in low logic mode is reduced to 0.05 by changing the defect rods.

A reversible bistate joint nimply optical logic gate using photonic crystals

In this work an optical reversible bistate joint NIMPLY (BJN) logic gate was designed using two-dimensional photonic crystals. The gate was designed using an asymmetrical waveguide with reference to a point defect introduced at the center of the structure. The desired logic functions were obtained in the forward and reverse state using the principle of interference of light. The defect rod radius and length of the waveguide using a line defect were chosen to introduce constructive and destructive interference of light. The BJN gate has a low footprint of 40.83 µm2 and the resonant wavelength was designed to be 1550 nm. The finite-difference time-domain method was used to attain the wave propagation and photonic bandgap for the proposed structure. The maximum contrast ratio of the reversible optical BJN gate in the forward and reverse states was found to be 25.11 dB and 24.86 dB, respectively.

Design and simulation of a very fast and compact all-optical Full-Subtractor based on nonlinear effect in 2D photonic crystals

In this paper, by using the non-linear effects and also destructive and constructive interferences between waveguides, we have designed and simulated an all-optical full-Subtractor based on two-dimensional photonic crystals. The proposed Subtractor has a very simple structure which is composed of 33 × 31 silicon rods immersed in air in a square lattice and involves three input ports (bits) and an additional waveguide to exhaust the unwanted light. We imposed some defect rods to control the behavior of the light. The used non-linear material, is a doped glass with 1.4 × 10–14 m2/w non-linear refractive index which is very greater than the non-linearity refractive index of silicon, 3.46 × 10–20 m2/w. Since the proposed structure is very simple and compact, it can be applicable in optical integrated circuits and optical calculations.

Very simple all-optical half-subtractor based on two-dimensional photonic crystals

In this paper, we proposed very simple structure for realizing the subtraction behavior based on two-dimensional photonic crystals. In the proposed structure, controlling of light is done by creating the input and output waveguides. After that, by imposing just one defect rod, and an extra waveguide we could fulfill the all-optical subtraction. We did not use any nonlinear material nor arc-type waveguide. The lattice constant and radii of rods for the slab waveguide with air holes are 414 and 124 nm respectively. These parameters are selected in a way that the behavior of this device is at the wavelength of 1550 nm. Time analysis showed that the rise time and the fall time of half-subtractor are around 0.5 ps and 0.1 ps respectively and the device is very fast.

Defect modes of two-dimensional photonic crystals composed of epsilon-near-zero metamaterials

The defect modes of a two-dimensional square array of epsilon-near-zero material (air) circular rods in air (an epsilon-near-zero material) were investigated in this study. A local defect was created by varying the radius of an epsilon-near-zero material (air) rod at the center of the array. It was found that the frequencies of the defect modes can be tuned to certain values in a wide range of a photonic band gap. However, the effective refractive index change due to the variations in the radius of an epsilon-near-zero material (air) defect rod was very small. The energy density of the defect modes was found to be strongly confined near the local defect rod but rarely inside the epsilon-near-zero material.

Compact eight-channel wavelength demultiplexer using modified photonic crystal ring resonators for CWDM applications

An eight-channel wavelength demultiplexer by cascading of ring resonators (RRs) in photonic crystal (PhC) structure is proposed in this paper. In designing of this demultiplexer, we used eight square-shaped PhC RRs with different refractive index (RI) of defect rods to generate a distinctive resonance wavelength. Each PhC RR has a specific resonance wavelength with tuning a variety of design parameters such as RI of a whole, defect and inner rods and radius of defect rods. In operating wavelength of λ0 = 1497 nm, the transmission power and quality factor (Q) of single RR are discovered as 96% and 1000, respectively. The average power transmission, channel spacing, crosstalk and full width at half maximum are found by finite difference time domain method to be about 96 ± 1%, 2.25 nm, − 35 dB and 1.5 nm, respectively. Simulation outcomes demonstrate that the designed demultiplexer has a proper operation. The footprint of the designed device is about ~ 115 μm2, which makes this device a promising for future photonic integrated circuits.

4-Channel Tunable Optical Demultiplexer Based on Nonlinearity Phenomenon in 2D Resonant Cavity Photonic Crystals

AbstractIn this paper, we propose a new structure based on photonic crystals to realise a demultiplexing operation for dense wavelength division multiplexing transmission systems. In this demultiplexer, the resonant cavities were responsible for selecting the wavelength. By imposing defect rods to these cavities, the modes could resonate at the desired frequencies. As we wanted to see the nonlinear effects, the material that was chosen for defect rods were doped glass. The refractive index of this glass in 1550 nm is 1.41. Increasing the input power causes variation in the refractive index of defect rods and as a result resonant condition of whole cavity alerts so a tenable demultiplexer can be investigated. Based on the results, the average pass bands of channels are near to 1.5 nm and the channel spacing is approximately 3.95 nm. The proposed demultiplexer acts in a near-complete transmission efficiency and the mean value of the crosstalk was −19 dB.

Mid-infrared sensing properties of a plasmonic metal–insulator–metal waveguide with a single stub including defects

A highly sensitive surface plasmon polariton-based sensor with a simple structure comprising a metal–insulator–metal waveguide with a single stub including several silver nanorod defects is designed and numerically investigated, using the finite element method, for application in refractive index sensors and temperature sensors. The simulation results show that the existence of silver nanorod defects in the single stub has a large influence on the sensitivity performance, which provides an additional degree by which to manipulate the system response at the nanometer scale. The refractive index sensitivity can reach as high as 5140 nm RIU–1 (RIU, refractive index unit) and the temperature sensitivity is about 2.05 nm °C−1, which can be further improved by varying the length of stub, the radius of the defect rods and the number of defects in the stub. The sensing characteristics of the proposed simple structure could pave the way for highly integrated optical circuits for use in nanoscale refractive index sensors and temperature sensors with the single stub including the defects.

Design and Simulation of Sensor Based on One Dimensional Photonic Crystal Metallodielectric with Two Defect

In this paper we report characteristics of a 1D metallodielectric photonic crystal with a two defect rod. Simulations of the field propagation for the corresponding Transverse Electric (TE) modes were carried out using Finite Difference Time Domain (FDTD) technique on Maxwell’s Equation. The results show that for certain chosen parameters of the transmittance varies if the refractive index of the defect rod is changed and that approximate linier changes for an refractive index range of 1.3 – 1.5 with a slight increase for a second defect change and a relatively steep decrease for a first defect change. A second defect index change can be used as the first defect sensitivity control The characteristics change due to variation of the defect rod radius is also considered for sensor design optimization

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.

An ultra fast optical reversible gate based on electromagnetic scattering in nonlinear photonic crystal resonant cavities

Optical reversible gates are required in realizing all optical digital data processing. In reversible gates, there is a one by one mapping between the input and output ports which helps us to recover the inputs from the outputs. In this paper we aim to design and propose all optical reversible XOR and XNOR gates based on electromagnetic scattering phenomenon in nonlinear photonic crystal structures. For realizing the proposed structures a special resonator was proposed which consists of two cross connected waveguides along with some linear and nonlinear defect rods. The proposed structure will be simulated using finite difference time domain method. The simulation results show that the maximum time delay for the proposed structures is about 10 ps. The truth tables for the both structures prove that there is one by one mapping between the inputs and outputs of the proposed structures.

A Four-Channel Optical Demultiplexer Using Photonic Crystal-Based Resonant Cavities

Abstract The aim of this paper was to propose and design an all optical four-channel demultiplexer using two-dimensional photonic crystals. To do so a resonant cavity was created by reducing the radius of the two adjacent rods. The radius of these defect rods was about 85 nm. The resonant cavity has a resonant mode at 1,557 nm. Then by using four resonant cavities with different radius values a four-channel optical demultiplexer was designed. The demultiplexer has four optical channels at λ1=1,537 nm, λ2=1,546 nm, λ3=1,553 nm and λ4=1,560 nm.

Designing a tunable acoustic resonator based on defect modes, stimulated by selectively biased PZT rods in a 2D phononic crystal

Reconfigurable phononic crystals (PnCs) and related devices are highly attractive because of their flexibility for different applications. We present the design procedure for a tunable acoustic resonator based on a 2D PnC, consisting of a periodic array of piezoelectric rods of radii 175 μm as inclusions arranged in air background. A single point defect devised by a rod of radius 161 μm, replacing one of the inclusions, plays the role of the acoustic resonator, leading to a defect frequency in the phononic band gap (fd ≈ 432 kHz). Applying a ∼1% strain to the defect rod, via an external voltage, tunes the defect resonant frequency within the phononic band gap. It is shown that the maximum tunability and the frequency shift depends on the defect size, and is achieved about Δfd = 440 Hz for the defect with the expense of descending quality factor. Considering the pattern of the localized pressure field, we introduce a multi-defect structure with five symmetric defect rods, corresponding to the maxima of field distribution. It is shown that maximum frequency shift of the dominant defect frequency is achieved about Δfd = 1.14 kHz for defect radius of 161 μm, when all five defect rods are strained. The proposed tunable filter based on multi-defect structure results in an enhancement of about 2.6 times in the maximum frequency shift, in comparison with the single defect structure, and introduces a promising approach for realizing tunable acoustic devices.

Simulant designing of an ultra-compact AND, OR logical gates based on two-dimensional photonic crystal waveguides

In this paper, we employed optical waveguides in a silicon rod base structure to realize AND, OR logical operation simultaneously based on two-dimensional photonic crystals. All of the structure is composed of silicon rods. Employing silicon rods of different radii as defect rods in optical waveguide filtered the desired wavelength. We utilized two similar waveguides as our input bits and two waveguides as AND and OR outputs. The overall footprint of the proposed device is 60 μm2 and hence is very compact. The time responses of device are about 0.5 ps and hence in conjunction with the mentioned characteristics suggest the use of the device for computational applications. The electric field distribution is obtained by the finite-difference time-domain method. In this paper, the logic state of ‘1’ and ‘0’ at output port is defined as the transmission is around ‘1’ and less than 0.25, respectively. The compact size of the proposed structure and the materials used make the proposed device suitable for optical integrated circuits.

Design of an optomechanical filter based on solid/solid phoxonic crystals

We simulate a phoxonic crystal which shows complete phononic and TM-polarized photonic bandgaps. The constituent materials are tungsten and polymethyl methacrylate, and we obtained these bandgaps with a filling factor of only 28%, which is very compatible with the fabrication method. A cavity was then defined that selects narrow passbands of optical and elastic waves. In order to maximize the quality factor, a defect rod is added in the output waveguide. The final structure filters an optical wavelength of 840 nm (with corresponding frequency of 357 THz) and an elastic frequency of 3.6703 GHz. Simulations are done by using finite element, plane wave expansion, and finite difference time domain methods.

Slow-light transmission with high group index and large normalized delay bandwidth product through successive defect rods on intrinsic photonic crystal waveguide

We proposed a strategy with successive cavities as energy reservoirs of electromagnetic energy and light-speed reducers introduced in the first and second rows of rods on the walls of an intrinsic photonic crystal waveguide (PCW) for slow-light transmission in the PCW concerning applications for optical communication, optical computation and optical signal processing. Subsequently, plane-wave expansion method (PWE) is used for studying slow-light properties and finite-difference time-domain (FDTD) method to demonstrate the slow-light propagating property of our proposed structure. We obtained group index as exceedingly large as 6123 with normalized delay bandwidth product (NDBP) as high as 0.48. We designed a facile but more generalized structure that may provide a vital theoretical basis for further enhancing the storage capacity properties of slow light with wideband and high NDBP.

Design and analysis of logic NOR, NAND and XNOR gates based on interference effect

We have developed and analysed logic NOR, NAND and XNOR gates based on two dimensional (2D) photonic crystals at a wavelength of 1.55 μm. The interference and self-collimation effects are used to design logic gates, which control the output by adjusting the phase difference to achieve constructive or destructive interference. The splitter is a line defect of the photonic crystal with a row of periodically arranged air rods. The radius of the defect rods depends on the function of the logic element. The use of these logic gates can reduce the size of logic devices.

An ultra-compact all optical full adder based on nonlinear photonic crystal resonant cavities

In this paper we are going to propose and design an all optical full adder based on photonic crystal. For realizing the proposed structure we will use four nonlinear resonant cavities inside a two dimensional photonic crystal. Nonlinear resonant cavities will be created by replacing the ordinary rods via defect rod made of nonlinear material such as doped glass. The simulation results show that the worst cases for logics 0 (the maximum normalized power in OFF state) and 1 (the minimum normalized power in ON state) are 3% and 53% for SUM port and they are 10% and 100% for CARRY port respectively. Also the maximum delay time for the proposed device is about 8 ps.