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Photonic crystals are periodic structures that are suitable for designing a variety of optical gates and logic circuits. In this paper, XOR and NOT logic gates are designed using two-dimensional square lattice photonic crystals. This structure consists of two inputs and one output, and the logical values ​​in the inputs and outputs are defined based on the amount of optical power. The plane wave expansion (PWE) method has been used in band structure calculations. The simulation results show that the proposed structure in a range of wavelengths has a photonic band gap that has a wavelength of 1.55 µm in this range. Therefore, the light sources placed in the inputs have a wavelength of 1.55 µm. Due to the use of a square structure that is easier to design and build, this structure is suitable for use in optically integrated circuits. Another advantage of this structure, in addition to its small dimensions, is the very low value of zero logic, which has increased the contrast ratio in the structure. The contrast ratio obtained in this structure is equal to 19.1 dB. [ABSTRACT FROM AUTHOR]

An optical analog to digital converter (OADC) comprises two main components: a nonlinear demultiplexer and an optical encoder. The nonlinear multiplexer converts the continuous input signal into three quantized discrete levels, while the optical encoder generates standard two-bit codes according to the different quantized levels. The optical Kerr effect is used to perform this process. For this purpose, several nonlinear rods that form a ring resonator are placed in the multiplexer. It can be said that their optical behavior can be controlled by light intensity. In this paper, analog to digital photonic crystal converters is investigated. The main purpose of this study is to provide designs that lead to the design of ADCs with high speed, small dimensions, high accuracy, and maximum sampling rate. [ABSTRACT FROM AUTHOR]

In this communication, the design of broad band optical reflector and selective polarization filter using a one-dimensional photonic crystal (1D-PC) containing superconductor and semiconductor layer has been proposed and investigated theoretically. The proposed design consists of alternate layers of yttrium barium copper oxide YBa2Cu3O7 (YBCO) and silicon (Si), respectively. The refractive indices of YBCO and Si layers are modulated as the function of temperature and wavelength both. This characteristic brings this study closer to actual physical implementation. To obtain the reflectance and transmittance properties of the proposed structure and to analyze the propagation characteristics of electromagnetic waves, the transfer matrix method (TMM) has been employed. The analysis of the reflectance spectra shows that near the critical temperature of YBCO layers no broad band reflection (from 0 to 85°) is observed. On the other hand, when the temperature is lowered below the critical temperature, ODR arises. The proposed YBCO/Si structure gives a broad band reflection band (from 1394 to 1621 nm (bandwidth 227 nm)) for both TE and TM modes of polarizations at 85 K. Also, at higher incident angles, the proposed structure acts as a selective polarization-based filter without introducing any defect in the geometry. [ABSTRACT FROM AUTHOR]

Photonic crystal channel drop filters (CDFs) play a vital role in optical communication owing to their ability to drop the desired channel. However, it remains challenging to achieve high-efficiency CDFs. Here, we demonstrate a highly efficient three-channel CDF with both high transmission and high quality (Q) factor based on a novel ring resonator that is in the middle of two waveguides. A dielectric column with a large radius replaces the homogeneously distributed dielectric columns inside the ring cavity to modulate the coupling ratio with a straight waveguide, thereby enhancing the transmission and Q factor. The transmission and Q factor of the single-cavity filter are 99.7% and 12,798.4, respectively. The mean value of the three-channel filter based on the basic unit can reach up to 94.6% and 10,617, respectively, and a crosstalk between −30.16 and −50.61 dB is obtained. The proposed CDFs provide efficient filter capability, which reveals great potential in integrated optoelectronics and optical communication. [ABSTRACT FROM AUTHOR]

The results of numerical simulation of the optical properties of a one-dimensional (1D) photonic crystal with a defect based on semiconductor-dielectric layers in the near-IR range are presented. The simulations used layers of silicon and silicon dioxide with optical thicknesses 3λ/4, λ/4 and 10λ/4. The influence of radiation incident angle on the spectral position of the defect's guidance band has been studied. It is shown that the sensitivity to the rotation angle lies within the limits of 6–20 nm/deg and 1.7–5.5 dB/deg, depending on the geometry of the sensor and the measurement method. This makes these photonic crystals promising for use in the rotation angle sensors as a sensitive element. [ABSTRACT FROM AUTHOR]

Photonic crystal channel drop filters (CDFs) play a vital role in optical communication owing to their ability to drop the desired channel. However, it remains challenging to achieve high-efficiency CDFs. Here, we demonstrate a highly efficient three-channel CDF with both high transmission and high quality (Q) factor based on a novel ring resonator that is in the middle of two waveguides. A dielectric column with a large radius replaces the homogeneously distributed dielectric columns inside the ring cavity to modulate the coupling ratio with a straight waveguide, thereby enhancing the transmission and Q factor. The transmission and Q factor of the single-cavity filter are 99.7% and 12,798.4, respectively. The mean value of the three-channel filter based on the basic unit can reach up to 94.6% and 10,617, respectively, and a crosstalk between −30.16 and −50.61 dB is obtained. The proposed CDFs provide efficient filter capability, which reveals great potential in integrated optoelectronics and optical communication.

An all-optical NOR gate is implemented using a two-dimensional photonic crystal waveguide. The paper provides a structure of an all-optical NOR gate constructed by introducing a line and point defect. The proposed NOR gate uses a hexagonal lattice structure with E shaped waveguide. The contrast ratio, response time and bit rate of three input NOR gate are 29.59 dB, 0.8 ps and 1.19 Tbps, respectively. The proposed gate is constructed with the operating wavelength of 1550 nm. The structure has been simulated and analyzed using Finite Difference Time Domain (FDTD) and Plane Wave Expansion (PWE) methods. It offers high contrast ratio, better response time with ultra-compact size. Hence it is suitable for high speed optical integrated circuits and switching devices. [ABSTRACT FROM AUTHOR]

In this article, T-junction, Y-junction, and E-junction power splitters based on 2D Photonic Crystals (PC) are premeditated. The two-dimensional FDTD method is employed for doing mathematical analysis and the plane Wave Expansion (PWE) method is used for attaining the band structure of the designed Photonic Crystal based optical power splitters. The power splitters are designed with the help of silicon rods having a 3.4 refractive index embedded on an air background which has a refractive index value of n = 1 arranged in a hexagonal manner. A hexagonal lattice is selected for the proposed design as it offers only a small photonic band gap area compared with a square lattice. Silicon material is preferred to design the proposed structure because it offers only low absorption C band spectral region. A comparative investigation of the proposed configuration is done on various aspects by utilizing the Finite difference time domain method and as a result, it is found that the E-junction photonic crystal-based power splitter delivered overall maximum transmission efficiency of 93% than T-junction's 60% and Y-junction's 79% and also it offers low insertion loss of 0.32 dB than 1.04 dB & 2.21 dB of Y-junction and T-junction respectively at the operating wavelength of 1.55 µm which is suitable for terahertz communication applications. With the help of photonic crystal, we can design optical components like splitters, resonators etc. with minimized dimensions in the range of micrometres. In general, the designed power splitters are very much appropriate for photonic integrated circuits (PIC) applications because of its miniaturized size of around 12.5 μm2. [ABSTRACT FROM AUTHOR]

Optical demultiplexers are among the crucial optical components that are required for efficient data transmission and all-optical processing. The article summarizes the recent developments on all-optical demultiplexers reported in the past decade based on the Photonic Crystal (PhC) platform. Detail description of the different demultiplexer designs reported along with the underlying parameters and performance metrics have been presented. The review is essentially clustered into two categories of the PhC namely rods in air (RIA), and holes in slab (HIS) structures that are being utilized in the reported designs. The comparative merits and demerits are also discussed with sufficient deliberation. Finally, some perspectives for future investigations have been discussed thereby providing the direction to upcoming researchers in this domain. [ABSTRACT FROM AUTHOR]

In this paper, we are going to design simulate an all optical OR gate based on two-dimensional photonic crystals. The proposed structure was designed based on phase shift keying technique. The working principle of the proposed structure is based on constructive and destructive interference of optical beams. The simulation results shows that the rise and fall times are 0.8 and 0.2 ps, respectively. [ABSTRACT FROM AUTHOR]

With the growth of technology and the need to integrate optical devices, photonic crystals (PhCs) will have great potential in designing and fabricating programmable photonic integrated circuits (PICs). This paper proposes two all-optical majority gates using the fluid infiltration approach in a PhC slab, which aims to design logic functions. Numerical results using the well-known plane wave expansion method show that the proposed fundamental PhC slab has three photonic band gaps (PBGs) in TE mode. The most important is in the wavelength range of 1.516 μm ≤ λ ≤ 1.743 μm, located in the attractive telecom C-band range. The results of light propagation inside the proposed gates using the finite-difference time-domain (FDTD) method reveal that both gates have a standard threshold of less than 0.28 for the logic zero and more than 0.35 for the logic one. The first and second proposed majority gates also have delays of 680 fs and 610 fs, respectively. One of the advantages of using the fluid infiltration approach is that there is no need to change the geometric dimensions of the structure for the desired application. That goal can be achieved only by replacing the fluid with another one. The proposed designs can be used as basic logic gates in the design of PICs. [ABSTRACT FROM AUTHOR]

We report the modeling and optimization of 1D periodic structures for second-order nonlinear effects. We present the work done in modeling to determine the location of the electromagnetic field in periodic structures. This modeling, carried out in a simple one dimension, makes it possible to mastery the properties of these structures and to study the influence of the different physical parameters on these properties. It allowed us to optimize structures for second-order nonlinear effects by focusing on the two essential factors of nonlinear polarization intensity and phase matching. This study, carried out in 1D structures, was extended to 1D planar structures (called 1.5D) used in guided optics and applied to the design of a 1.5D photonic crystal structure made in a Gallium Nitride layer for the second harmonic generation. [ABSTRACT FROM AUTHOR]

Multiplexers are widely used logic circuits that connect a number of inputs to an output. These circuits are used to create logic functions. This article designs and simulates a 2 × 1 multiplexer based on 2D photonic crystals. The structure of this multiplexer includes dielectric rods in an air background. At the input, there is a ring resonator between two waveguides. This multiplexer’s structure is relatively small, with 14 × 15 rods. The operating wavelength of this logic circuit is 1.55 μm, which falls within the photonic band gap. The PWE method was used to simulate the band structure, and the FDTD numerical calculation method was used to calculate time.

Photonic crystals are dielectric structure materials with photonic band gaps which are composed of matters with different dielectric constants and arranged in space periodically. The slow photon and band gap reflection in the photonic band gap can promote the photonic capture and control the interaction between light and matter. Based on the unique optical properties and large specific surface area of photonic crystals, the photonic crystal structure is introduced into the design of semiconductor photocatalytic materials, which can effectively enhance the photocatalytic reaction activity. The preparation methods of three-dimensional photonic crystals and slow photons effect was introduced in this paper,the research progress was especially summarized in the inverse opal photonic crystal as catalysts in wastewater purification of light, hydrogen production, carbon dioxide conversion and etc,and for the challenge faced by the photonic crystal light catalyst, multilayer three-dimensional photonic crystals with different refractive index and the periodicity were put forward, in order to promote photonic crystals applications in the field of photocatalysis.

We propose a flexible design for tunable bandpass biomedical color filter based on one-dimensional photonic crystals with introducing defect layers into one dimensional periodic structure which permits localized modes to exist with frequency inside photonic band gap (PBG). In the proposed structure we can tune localized modes for manifesting different colors by selecting a specific wavelength in the visible light spectrum and also we tuned localized modes in PBG for RGB wavelengths applicable in biomedical systems. With changing the defect layer refractive index, the tuning of the frequency has been done and therefore this structure is suitable for optical biomedical bandpass filter.

The advanced technological development of photonics is very rapid compared to other technologies. Photonic crystal (PC)-based combinational and sequential circuits are most widely used for photonic integrated circuits. In this paper, we have mainly focused on the adder where the output is a pure function of the present input only. A half adder is a type of adders, which adds two binary digits and gives an output plus a carry value. The half adder contains two input ports and two output ports as sum and carry. In this attempt, two-dimensional (2D) PCs-based half adders that are designed either square or triangular lattice using various mechanisms with different materials are presented here. The adders are most widely used in program counters, digital instruments and in microcontrollers. [ABSTRACT FROM AUTHOR]

In this paper, Two Dimensional Photonic Crystal (2DPC) based 4*2 and 8*3 encoders are devised using Y shaped waveguides. The proposed encoder operates at 1550 nm. In this attempt, initially, 4*2 encoder is designed and its corresponding structural parameters, such as, refractive index of the rod, radius of the rod and lattice constant, are optimized in order to attain better functional parameters. The primary functional parameters of the encoders are normalized power, contrast ratio, response time and bit rate. The Finite Difference Time Domain (FDTD) method and Plane Wave Expansion (PWE) method are utilized to analyze the performance parameters and Photonic Band Gap (PBG) of the encoder, respectively. As the proposed encoder is performing well, it is applicable for high speed optical integrated circuits. [ABSTRACT FROM AUTHOR]

This study investigates the propagation of electromagnetic waves through a one-dimensional quasi-photonic crystal with the transfer matrix method. Our proposed structure consists of two types of double-negative metamaterials, organized according to the Thue–Morse sequence law. The results show that changing the structure via quasi-periodic arrangements makes the outcome more varied than applying the absolute periodic arrangement. Given that, our desirable results of interest are more convenient to achieve. The structure completely stops both s and p polarization at the lower frequencies, for all incidence angles. It also partially stops s and p polarization, at higher frequencies. Moreover, the achieved transmittance spectrum contains several omnidirectional band gaps, which remain invariant with changes in the incidence angle. The oscillation of the transmittance values also becomes more intense at higher orders of the period number. This study could pave the way for optimizing photonic crystal circuits, splitters, switches, etc. [ABSTRACT FROM AUTHOR]

In this letter, a 180° ring-shaped hybrid based on the photonic crystal structure (PCS) is presented. The ring hybrid is designed for the operation wavelength of 1550 nm. Initially, a 180° hybrid is a design based on conventional microwave procedures. Different wave behavior inside the structure in THz and microwave frequency band has caused the wave propagation in this structure to change especially in terms of phase. By analyzing the field distribution within a structure, the rod arrangement is modified. In proposed structure, the phase difference between the output ports is greatly improved (about 90°). Also, by reducing the leakage and improving the matching, the output power of the ports tends to half power. Moreover, 32 nm wavelength shift is improved. The proposed structure’s reflectance value is less than 20 dB at the desired wavelength. The power splitting ratio between the two output ports is improved up to −3.7 dB and the power of the isolated port is less than −20 dB. This work has been analyzed using the FDTD method. [ABSTRACT FROM AUTHOR]

In this paper, Two Dimensional Photonic Crystals (2DPC) based all-optical two/three input OR gate is proposed and designed. A logic gate is an elementary building block of a digital circuit. The proposed all-optical OR gate is designed by creating Y shaped defect with ring resonator in a hexagonal lattice structure. The performance of the proposed all-optical OR gate is investigated using the Plane Wave Expansion (PWE) and Finite Difference Time Domain (FDTD) method. The functional parameters namely normalized efficiency, contrast ratio, response time and bit rate, are calculated. The proposed all-optical OR gate operates at a wavelength of 1550 nm. The size of the proposed structure is compact in nature. It offers high contrast ratio and minimum delay time. Hence it is suitable for optical processors, high speed optical integrated circuits and switching devices. [ABSTRACT FROM AUTHOR]

Recently, a lot of research has been carried out on different techniques to improve the performance of microstrip patch antenna (MPA). Here, we have overviewed and summarized various techniques which has been invented in past to improve the gain and of the MPA. The addition of frequency selective surface (FSS), metallic reflectors, metamaterial, parasitic patches, air gap, superstrate, shorting pins, defective ground structure and partial substrate removal are some known techniques to improve antenna gain. This paper helps to decide the best technique of gain improvement for MPA. [ABSTRACT FROM AUTHOR]

The enhancement of Raman signals using photonic crystal structures has been the subject of numerous experimental and theoretical studies, leading to a variety of issues and inconsistencies. This paper presents a comprehensive experimental investigation into the impact of alignment between the laser excitation wavelength and the specific position of the photonic band gap on signal enhancement in Raman spectroscopy. By employing one-dimensional (1D) porous silicon photonic crystals, a systematic analysis across a large number of spectra was conducted. The study focused on examining the signal enhancement of both the Raman ∼520 cm–1 silicon band, representing the constituent material of photonic crystal, and the most prominent Raman bands of crystal violet, used as a probe molecule. The probe molecules were both infiltrated into and adsorbed on top of the photonic crystal structure. The obtained experimental results for the contribution of 1D photonic crystals to Raman signal enhancement are much smaller compared to most predictions. The Raman signal of silicon and the signal from the probe molecule are enhanced ≤2.5 times when the laser excitation aligns with the edge of the photonic band gap, strictly defined as the position at the very bottom of the reflectance peak. The results have been discussed within the context of theoretical explanations. [ABSTRACT FROM AUTHOR]

In this paper, Using a 2D photonic crystal and a novel square ring resonator,several compact and simple structures have been introduced in the present paper toconstruct optical add/drop filters and multi-channel filter. The difference structures hasbeen designed and simulated by using the proposed square ring resonator and differentdropping waveguides. To do analyses, the finite-difference time-domain method and theplane wave expansion have been used. The three add/drop filters can separate thewavelength of 1554 nm with a transmission coefficient of 100 %, quality factor of 1295and bandwidth of 1.2 nm. The models of structures are simulated by the RSOFT CADLayoutsoftware. The results, flexibility and simplicity of structures have caused fromtheir used to designing of an optical multi-channel filter with a channel spacing of 1.5nm. The advantages of this design include the channel spacing, quality factor,transmission coefficient and bandwidth which are suitable for applicability in opticalcommunication systems such as wavelength division multiplexing systems.

Calculations were performed using the transfer matrix of one-dimensional photonic crystals with low contrast and asymmetric structures of different periods. Such structures have been found in many plants. When joining two successively connected sublattices with different periods, an increase is observed in the amplitude of the electromagnetic field and the density of photon states inside the structure, and their change depends on the asymmetry of the thickness of the sublattices.

Optical channel drop filter (OCDF) plays a key role in optical communication networks for filtering the individual wavelength among the group of channels in wavelength division multiplexing systems. There are several channel drop filters with different design mechanisms available in the literature, but those structure dimensions are not compact enough for the photonic integrated applications. Hence, in this paper, a compact and efficient OCDF is developed in the triangular lattice PC structure based on diamond-shaped photonic crystal ring resonator (PCRR) mechanism combined with micro cavity resonator (MCR). The developed OCDF is analysed for different operating wavelengths by considering the different positions of MCR around the main PCRR. Based upon the position of the MCR around PCRR, the three dropping wavelengths such as 1540 nm, 1550 nm, and 1570 nm are observed at the output waveguides with 100% dropping efficiency. Then the structural and performance parameter comparison is done between the proposed and existing structures in terms of device dimension, dropping efficiency, and quality factor. It is depicted through the results that the quality factor and the device dimension are better than that of the existing structures for 1550-nm wavelength. [ABSTRACT FROM AUTHOR]

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In this paper, OR and AND logic gate functions are realized in a triangular lattice using two dimensional photonic crystal (2DPC). The proposed design of logic gates are based on the phenomenon of resonance and interference. The OR and AND logic gates are constructed by varying the rod radius and by creating Y-shaped waveguide in the structure. Initially, the OR gate is designed with reference input and without reference input and it's extended for AND gate. The functional parameters of the logic gates such as response period, bit rate, contrast ratio and field distribution of different logics are investigated through 2D finite difference time domain (FDTD) method. The contrast ratio, response period, bit rate and size of the three input OR gate are 30 dB, 0.52 ps, 1.92 Tbps and 12.6 μm×11 μm, respectively. Similarly, the aforementioned parameters are estimated for two input OR gate, two input AND gate and three input AND gate. The proposed logic gates are highly desirable for integrated optics. [ABSTRACT FROM AUTHOR]

In this paper, Two Dimensional Photonic Crystals based Add Drop filter (ADF) is designed for DWDM applications. The existing work concentrates in Coarse Wavelength Division Multiplexing and few filters reported for DWDM with non-uniform channel spacing, and low quality factor. The proposed ADF enhances the quality factor using Rounded Square Ring Resonator (RSRR) for ensuring efficient bandwidth in supporting WDM systems. The design consists of bus waveguide, drop waveguide and RSRR with inner quasi-square ring in the square lattice. The dielectric constant of the Si rod is 11.68 which are hosted in the air. The line defect is created by removing 4 rods (Quasi ring) in the center of the inner square ring. The line defect in the ring resonator is used to reduce the radiation field components surrounded by the resonator. The performance parameters of ADF are investigated using 2D Finite Difference Time Domain algorithm. The proposed ADF drops a channel at 1636.2 nm, with the bandwidth of 0.7 nm, high quality factor of 2337, and the dropping efficiency of about 100%. The size of the device is 412.76 µm2. It is highly sufficient to support WDM systems for future Photonic Integrated Circuits (PIC). Further, the impact of functional parameters such as transmission efficiency, quality factor, bandwidth are investigated by varying the structural parameters, namely, adjacent rod radius, scatterer rod radius, coupling rod radius, lattice constant, inner rod radius and rod radius. [ABSTRACT FROM AUTHOR]

In the present report, a photonic crystal based micro-ring resonator (MRR) structure is proposed which is very compact in size and has very fast response and is employed for temperature sensing purpose. Temperature sensing application for both the single MRR and cascaded MRR is illustrated in this paper. The sensitivity of the reported structure is increased from 2.9 nm/°C to 3.4 nm/°C by cascading two MRR. The refractive index of the material is subjected to change with the variation in temperature which results in the shift of the resonant wavelength of the proposed sensor. The finite difference time domain (FDTD) simulation is utilized to see the transmission spectrum of the proposed structure and analyzing the shift in the resonance wavelength the temperature is calculated. The proposed design is simple, reliable and may be integrated into different transducer and sensing applications. [ABSTRACT FROM AUTHOR]

In this paper, the transmission properties of a one-dimensional photonic crystal containing molybdenum disulfide ( M o S 2 ) monolayers are studied theoretically using the transfer matrix method. The considered photonic crystal structure contains M o S 2 monolayers, which are embedded between dielectric layers. It is found that the presence of M o S 2 causes to creation of a new photonic band gap which is almost omnidirectional and also polarization insensitive. Besides, the spatial distribution of the tangential component of the electric field for a TE-polarized plane wave has been shown for some wavelengths. It is found that the behaviour of the waves from the M o S 2 induced band gap is different from that of Bragg gaps. Finally, the Gaussian beam propagation inside and outside of the photonic crystal have been simulated using the finite element method for critical wavelengths and different incident angles which verify the behavior of field profiles. [ABSTRACT FROM AUTHOR]

In this paper the design and analysis of two dimensional photonic crystals based all optical AND logic gate is investigated. A logic gate implements a Boolean function and thus performs a logical operation on one or several logic inputs in order to produce a single logic input. The proposed all optical AND gate is designed with line and point defect using a hexagonal lattice with "Y" shaped defect. In order to meet the requirements for high speed networks the proposed gate designed. The functional parameters such as contrast ratio, bit rate, normalized efficiency and response time are calculated. The performance of the AND gate is analyzed by using the Finite Difference Time Domain method. The proposed logic gate is designed to operate at 1550 nm. It provides high contrast ratio and minimum delay time. Hence it is suitable for optical sensors and optical integrated circuits. [ABSTRACT FROM AUTHOR]

The optical transmission spectra proprieties of the onedimensional quasi-periodic multilayered photonic structures according to the Rudin-Shapiro distribution are studied theoretically in this paper by using a theoretical model based on the transfer matrix approach for normal incidence geometry. The influence of the layer number has been studied, i.e. the iteration order of the generating sequence of the quasi-periodic structure on the structure spectral behavior and the width of the Photonic Band Gap (PBG). It was found that the width of the PBG is proportional to the index contrast. [ABSTRACT FROM AUTHOR]

In this paper, an optical filter based on a two dimensional photonic crystalring resonator (PCRR) with triangular lattice is designed and presented. For thispurpose, the effects of positioning, arrangement and the number of the inner rods of thedual-curved PCRR on the performance characteristics of our optical filter such as thetransmission coefficient and the quality factor have been fully investigated. Calculationresults show that a transmission coefficient of 100% with a quality factor of 2400 at theoperating wavelength of nearly 1576 nm can be achieved. The proposed optical filtercomparatively performs better than the previously reported ones. In addition, thisstructure can be used for the design of optical multi-channel demultiplexer. To study thephotonic band gap of our structure, the plane wave expansion (PWE) method has beenused and the finite-difference time-domain (FDTD) method has also been employed toanalyze the optical behavior of the proposed device.

In this paper we combined an optical mixer via photonic crystal ringresonator to propose an all optical 1 to 2 decoder. The main idea used in this paper isbased on controlling the optical behavior of the resonant ring via optical powerintensity. We know that resonant wavelength of the photonic crystal ring resonator isvery sensitive upon the refractive index of dielectric rods, on the other had the refractiveindex of dielectric materials depend on the optical power intensity. Therefore we canchange the resonant wavelength of the resonator by increasing the optical powerintensity up to adequate amount. The final structure has two output ports whose workingstates can be controlled by one input port. When I is OFF, the O1 port will turn ON andO2 is OFF, when I is ON, O1 turns OFF and O2 turns ON. The proposed structure workscompletely in optical domain without any electronics.

In this paper, the optical spectra of one-dimensional photonic crystal (PCs) are numerically investigated in UV, Visible and Infrared ranges. PCs consisting of a HTc superconducting material (YaBa 2 Cu 3 O 7) are sandwiched between dielectric layer (SiO 2 or AlN) and semiconductor layer (GaAs), where superconducting layer is considered as defects. Using transfer matrix method, all the numerical results are performed and inferred that photonic band gap shifted to higher wavelengths by increasing the temperature. It is found that when the temperature increases the PBG shifted to a long wavelength. When the defect is used in structure as dielectric or superconductor, the peak appears in PBG and his value increases as the temperature increases. [ABSTRACT FROM AUTHOR]

Anodic titanium oxide is a promising material for the formation of photonic crystal structures due to its high refractive index, stability in acidic media, and semiconductor conductivity. One-dimensional photonic crystals are obtained by the anodization of titanium with triangle wave modulation of the voltage versus the charge density. The dependence of the position of the photonic band gap on the charge density per anodizing cycle is studied. The reflection coefficient within the photonic band gap of the obtained samples reaches 70%. Taking into account chemical dissolution of the pore walls during anodic oxidation and gradual reduction of the structure period along the film thickness make it possible to obtain photonic crystals based on titanium oxide with a record value of the Q factor of 9.6. [ABSTRACT FROM AUTHOR]

Mesoporous silicon photonic crystal based composites containing silver nanoparticles are shown to provide new substrates for the improvement of SERS. The enhancement of SERS depends on the localized surface plasma resonance (LSPR) of the obtained material and the enhancement of Raman polarizability that results from the increasing interaction time of the light and matter of the multilayer structure. The electric field on the photonic crystal surface is stronger than that on the single-layer film by the finite-element time-domain method (FETD). While the surface field distribution of photonic crystals is in a narrower region from the surface than that of single-layer films. Thus, Ag nanoparticles are deposited on the two types of porous silicon samples, the enhanced electric field on the surface of photonic crystals is conducive to achieving stronger the strong LSPR response, which leads to the enhancement of Raman optical signal. SERS activity of the substrates was tested using rhodamine 6G as the probe molecules. SERS on photonic crystal device substrates are superior to that on the single-layer structure substrates, and shows a gain of five times. In addition, the enhancement of Raman signals also reduces the threshold of the detection down to $1.0\times 10^{-13}\text{M}$. The strategy described here is a low-cost process with potential for a sensitive Raman sensor based photonic crystal for biological detection. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In this work, the design and the performance of a two dimensional photonic structure with hexagonal geometry is numerically investigated by plane wave expansion (PWE) method. The structure consists in a zinc oxide (ZnO) substrate patterned in a hexagonal configuration with periodic holes with different radius. The photonic crystals exhibited band gaps in the near infrared wavelength range. This kind of photonic structures can be used for a wide range of optoelectronic applications. [ABSTRACT FROM AUTHOR]

In this article, we proposed a four-channel optical demultiplexer based on photonic crystal resonant cavities. For performing wavelength selection task, we used four resonant cavities with different lengths in order to choose four channels with different wavelengths. The average channel spacing of the structure is about 1 nm and the minimum transmission efficiency is 90 %. The bandwidths of the channels are the same and equal to 0.8 nm. [ABSTRACT FROM AUTHOR]

Abstract In this paper, we study the thermal effects on photonic band structures in a hexagonal lattice. We consider that the lattice is composed of GaAs rods embedded in air with circular and triangular cross sections. Using the plane wave expansion method, we found that by increasing the temperature, the contrast of the refractive index increases and causes a shift of the photonic band structures to regions with lower frequencies. By increasing the size of triangular scatterers, the width of the photonic band gap (PBG) for TM polarization increases in comparison with the PBG of the circular scatterers. In addition, we discuss the effects on the band structure when we eliminate the circular and triangular rods in the crystal's lattice. We found that the width of the PBG remains unchanged in the presence of a defective mode inside, which shifts at lower frequencies when the temperature increases. There is evidence of greater radiation confinement in the lattice composed of circular scatterers. [ABSTRACT FROM AUTHOR]

Anodic titanium oxide (ATO) one-dimensional photonic crystals (PhCs) are materials with uniaxial periodic modulation of porosity. A periodic change of an effective refractive index caused by porosity modulation results in the formation of photonic band gaps (PBGs). The non-uniform dissolution of ATO cell walls during the fabrication process hampers the obtaining of a strict optical periodicity of ATO PhCs. Recently it was found that the dissolution of ATO cell walls is accelerated by anodic polarization. However, the main factor controlling the accelerated dissolution of ATO cell walls during anodizing remains unclear. In this study, the correlation between ATO PhC porosity and the charge density is discussed. The dependencies of the spectral photonic band gap (PBG) position and PBG reflectance on the charge density are studied experimentally. The findings open a pathway to the synthesis of ATO PhCs with flawless optical periodicity and high PBG reflectance. [Display omitted] • Charge density is a key factor affecting the porosity of anodic titanium oxide films. • Blue shift of the photonic band gap occurs with the increase in charge density. • Photonic band gap reflectance increases with passing of the charge. • Method of the direct observation of porosity variation along the nanotubes is proposed. [ABSTRACT FROM AUTHOR]