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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]

This paper proposes co-planner waveguide (CPW)-fed modified fractal antennae for wideband and multiband applications. The proposed antennas have a resonance frequency in the range of 24–40 GHz with 40 × 40 mm2 dimensions. The corporate CPW (Coplanar Waveguide) feeding technique is integrated with the ring, meander line, and periodic staircase with a slot pattern and augmented by conductive graphene for Electromagnetic Band Gap and Photonic Band Gap structures on the opposite side of the Substrate. This integration significantly enhances antenna performance, manifesting superior radiation properties, increased gain, enhanced directivity, and resonating behavior concerning fractal antennae. The proposed PBG and EBG fractal antennas exhibit peak directivities ranging from 9.95 to 9.48 dBi for different angles (Phi = 0°, Phi = 90°, Theta = 90°) with beam scanning and pencil beam properties, with maximum return losses of 47 dB and 30 dB for PBG and EBG designs, respectively. The covered bandwidths include 26–28 GHz, 28.4–36.3 GHz, and 25–26.5 GHz, 27.7–29.8 GHz, 31–33 GHz, 34.1–40 GHz, compatible with 5G NR bands n257, n258, n259, n260, and n261, and ground-based radio navigation applications. Simulations using CST and validations with vector and spectrum analyzers confirm these results. [ABSTRACT FROM AUTHOR]

All-optical half subtractor (AHS) is the very essential circuit to perform very-high speed operations in the present electronic world. The paper focuses on implementation of AHS by using photonic crystal (PhC) T-shaped waveguides. This structure works on beam interference pattern, and the output results are simulated using finite-difference time-domain method (FDTD). The suggested structure is of compact size of 27.72 μm2 and good contrast ratio (CR) of 15.79 for difference (Diff) and 11.22 for borrow (Borr) with the bit rate of 90.9 Tbps that can bring out in optical signal processing. [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]

An additively stacked quasi-self-similarity Sierpinski Carpet-based fractal antenna embedded over a photonic band gap substrate is proposed in this paper. The proposed structure is designed for continuous in-vivo monitoring of cardiac Troponin I (cTnI) levels in the blood released from the heart muscles even with a trivial malfunction. The total size of the antenna biosensor is 0.4 λ0 × 0.33 λ0 × 0.025 λ0 and is assumed to be implanted over a leadless pacemaker. The substrate material used is Teflon (εr = 2.1) with gold as patch material to accomplish as bio-receptor. The frequency band of 0.1–3 Terahertz is considered for the design as per IEEE standard. Result validation without bio-model is performed through High Frequency Structural Simulator, Computer Simulation Technology, Advanced Design System, and COMSOL simulation software. The dielectric constant values of blood, myocardium, and other biological parameters are calculated based on the Cole–Cole model using Matrix Laboratory for further analysis. Those values are incorporated in the design to imitate a bio-model, to check the variation in frequency with regard to permittivity, in turn corresponding to troponin level change. [ABSTRACT FROM AUTHOR]

Polycrystalline Ta2O5 inverse opal (IO) photonic crystal powders were synthesized using PMMA colloidal crystals as sacrificial templates. We prepared Ta2O5 IO powders with vibrant structural colors at UV–vis wavelengths. The photonic bandgaps (PBGs) in the Ta2O5 IO powders red-shifted as a function of both the macropore diameter and the refractive index of the medium filling the macropores. Owing to their polycrystalline structure, the Ta2O5 IO powders exposed PBGs for various FCC facets, making investigation of their optical properties significantly more complex than Ta2O5 IO thin films that preferentially expose only (111) planes as studied previously. Due to the overlap of the PBGs from different FCC facets and the defects that cause light scattering, much of the typical angle-dependent structural color observed in IO thin films was lost in the Ta2O5 IO powders. This study offers new insights into the optical properties of IO powders.

Abstract This paper seeks to progress the field of topological photonic crystals (TPC) as a promising tool in face of construction flaws. In particular, the structure can be used as a novel temperature sensor. In this regard, the considered TPC structure comprising two different PC designs named PC1 and PC2. PC1 is designed from a stack of multilayers containing Silicon (Si) and Silicon dioxide (SiO2), while layers of SiO2 and composite layer named hyperbolic metamaterial (HMM) are considered in designing PC2. The HMM layer is engineered using subwavelength layers of Si and Bismuth Germinate, or BGO ( $${\text{Bi}}_{4}{\text{Ge}}_{3}{\text{O}}_{12}$$ Bi 4 Ge 3 O 12 ). The mainstay of our suggested temperature sensor is mainly based on the emergence of some resonant modes inside the transmittance spectrum that provide the stability in the presence of the geometrical changes. Meanwhile, our theoretical framework has been introduced in the vicinity of transfer matrix method (TMM), effective medium theory (EMT) and the thermo-optic characteristics of the considered materials. The numerical findings have extensively introduced the role of some topological parameters such as layers’ thicknesses, filling ratio through HMM layers and the periodicity of HMM on the stability or the topological features of the introduced sensor. Meanwhile, the numerical results reveal that the considered design provides some topological edge states (TESs) of a promising robustness and stability against certain disturbances or geometrical changes in the constituent materials. In addition, our sensing tool offers a relatively high sensitivity of 0.27 nm/°C.

This paper seeks to progress the field of topological photonic crystals (TPC) as a promising tool in face of construction flaws. In particular, the structure can be used as a novel temperature sensor. In this regard, the considered TPC structure comprising two different PC designs named PC1 and PC2. PC1 is designed from a stack of multilayers containing Silicon (Si) and Silicon dioxide (SiO2), while layers of SiO2 and composite layer named hyperbolic metamaterial (HMM) are considered in designing PC2. The HMM layer is engineered using subwavelength layers of Si and Bismuth Germinate, or BGO ( Bi 4 Ge 3 O 12 ). The mainstay of our suggested temperature sensor is mainly based on the emergence of some resonant modes inside the transmittance spectrum that provide the stability in the presence of the geometrical changes. Meanwhile, our theoretical framework has been introduced in the vicinity of transfer matrix method (TMM), effective medium theory (EMT) and the thermo-optic characteristics of the considered materials. The numerical findings have extensively introduced the role of some topological parameters such as layers' thicknesses, filling ratio through HMM layers and the periodicity of HMM on the stability or the topological features of the introduced sensor. Meanwhile, the numerical results reveal that the considered design provides some topological edge states (TESs) of a promising robustness and stability against certain disturbances or geometrical changes in the constituent materials. In addition, our sensing tool offers a relatively high sensitivity of 0.27 nm/°C. [ABSTRACT FROM AUTHOR]

The optical Encoder plays a crucial role in optical computing and communication applications. This proposed work employs an innovative technique to design and simulate a Silicon Y-shaped 2D Photonic Crystal unique structure for an all-optical 4 × 2 encoder. The proposed structures consist of silicon rods arranged in a square lattice within a background of air. The frequency modes and encoder design were studied using the PWE method, while the proposed design underwent numerical analysis, simulations, and optimizations using the FDTD numerical solution approach. The structure is engineered to ensure maximum power confinement at the output of the silicon PC-based 4 × 2 Encoder. With a low power loss and outstanding contrast ratio, the structure is specifically designed for the 1550 nm wavelength range. This 4 × 2 encoder boasts a compact footprint of 295μm2, a minimal delay of 0.17 ps, an impressive contrast ratio of 31.14 dB, a minimum response time of 0.24 ps, a steady state time of 1.03 ps, a bit rate reaching 4.17 Tbps, minimal cross-talk -31.14 dB, an extinction ratio of 31.14 dB, and an insertion loss of -3.18 dB. Considering these attributes, it comes highly recommended for applications in optical signal processing and photonic integrated circuits. [ABSTRACT FROM AUTHOR]

Structural color is a remarkable physical phenomenon that exists widely in nature. Unlike traditional color rendering methods, they are realized mainly through micro/nanostructures that interfere, diffract, scatter light, and exhibit long‐life and environmental‐friendly color effects. In nature, a few organisms use their color‐changing system to transmit information, such as courtship, warning, or disguise. Meanwhile, some natural inorganic minerals can also exhibit structural colors. Learning from nature, scientists have achieved large‐scale structural color design and manufacturing technology for artificial photonic crystals. Photonic crystals have a unique microstructure that forms a band gap under the action of the periodic potential field, consequently causing Bragg scattering due to the periodic arrangement of different refractive index media within them. Because of the apparent photonic band gap and the ability to form local photons at crystal defects, photonic crystals have been extensively studied in recent years and have broad application prospects in photonic fibers, optical computers, chips, and other fields. In this review, the research, properties, and applications of photonic crystals in recent years are presented, as well as insight into the future developments of photonic crystals. [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]

Integrating photonic crystals (PCs) into the design of a photocatalyst can significantly enhance its light‐harvesting capability. PCs can manipulate the propagation of light uniquely within a material and reduce its group velocity, thereby enhancing the absorption factor for photocatalysts. However, the slow photon effect in photoactive films with chiral nematic structures has not been reported yet, especially at the blue edge of the photonic bandgap. This work proposes a straightforward one‐pot method to fabricate various photonic films with chiral nematic, namely g‐C3N4/SiO2, TiO2/SiO2, and g‐C3N4/TiO2/SiO2. The sol‐gel biotemplating formulation using cellulose nanocrystals successfully leads to the elaboration of films exhibiting variable iridescent colors with photonic bandgap from UV to visible range. The tunable wavelength of the Bragg peak reflection offers the opportunity to access a region with a slow photonic effect, which directly impacts the light‐harvesting properties of the photoactive material. It is demonstrated that the H2 generation is significantly enhanced when the blue edge of the photonic bandgap position overlapped with the absorbance band of the photocatalyst. These results offer the opportunity to design photonic materials with chiral nematic structure and optimize the photocatalytic performance for energy application. [ABSTRACT FROM AUTHOR]

In this paper, we have designed and simulated all-optical logic gates with multi-functionalities based on two-dimensional photonic crystals. All-optical logic gates such as AND, OR, XOR, NOR and NAND are designed, simulated and optimized at 1550 nm wavelength. The operations of the proposed logic gates are based on the phenomenon of interference of optical waves and resonance in the cavity and analyzed with performance parameters such as contrast ratio, transmittance ratio and insertion loss. Based on the identical scheme of photonic crystal structure, multi-functionalities can be realized through tuning refractive index induced by applying voltage or manipulating the initial phase of the input optical wave signals. As a result, the proposed all-optical logic gates with multi-functionalities may contribute to the design of advanced photonic integrated devices. [ABSTRACT FROM AUTHOR]

Recently, UVC LEDs, which emit deep ultraviolet light, have found extensive applications across various fields. This study demonstrates the design and implementation of thin films of three-dimensional photonic crystals (3D PhCs) as reflectors to enhance the light output power (LOP) of UVC LEDs. The 3D PhC reflectors were prepared using the self-assembly of silica nanospheres on a UVC LED lead frame substrate via the evaporation-induced method (side) and the gravitational sedimentation method (bottom), respectively. These PhCs with the (111) crystallographic plane were deposited on the side wall and bottom of the UVC LED lead frame, acting as functional materials to reflect UVC light. The LOP of UVC LEDs with 3D PhC reflectors at a driving current of 100 mA reached 19.6 mW. This represented a 30% enhancement compared to commercial UVC LEDs with Au-plated reflectors, due to the UVC light reflection by the photonic band gaps of 3D PhCs in the (111) crystallographic plane. Furthermore, after aging tests at 60 °C and 60% relative humidity for 1000 h, the relative LOP of UVC LEDs with 3D PhC reflectors decreased by 7%, which is better than that of commercial UVC LEDs. Thus, this study offers potential methods for enhancing the light output efficiency of commercial UVC light-emitting devices. [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]

One-dimensional photonic crystals with an arbitrary number and spectral position of photonic band gaps in the optical spectral range are experimentally demonstrated. The absence of mutual influence of the photonic band gaps was shown. No features corresponding to higher harmonics or combination frequencies were found in the spectral response of the multifrequency photonic crystals created. [ABSTRACT FROM AUTHOR]

In this work, we investigate the photonic stop band of multilayers, which is the simplest possible 1D photonic crystal, using MIT electromagnetic equation propagation software. The transmission spectra were simulated, and the effect of the number of layers and the contrast in the dielectric constant on the photonic band gap was studied. The ZnO/SiO2 multilayer was fabricated using radio frequency magnetron sputtering. The refractive indices of ZnO and SiO2 were found from the absorption spectra. The transmission spectra of the photonic crystals with eleven layers were studied using a UV–visible spectrophotometer. A dip in the transmission spectra in the wavelength range of blue was observed. The experimental result matched the simulated transmission spectra. The cross-sectional view of the multilayers was observed using a field emission scanning electron microscope. [ABSTRACT FROM AUTHOR]

The transformation of the graphene-containing optical spectra photonic-crystal structure with a change in the chemical potential (μ) of graphene is studied. In the period of the structure, one layer is a graphene-containing periodic medium (SiO2/Gr)n, and the second layer is assumed to be made of pure silicon. In the case of unexcited graphene (μ = 0), the absorption in the structure exceeds the reflection and transmission for frequencies outside the photonic band gaps. Within these zones, most of the incident radiation is reflected, and there is no transmission at all. As μ increases outside the band gaps, the absorption decreases in the low-frequency region, and the transmission increases the stronger, the greater μ. In a structure with an inversion defect inside the band gaps, either suppression or significant rearrangement of the defect mode takes place. [ABSTRACT FROM AUTHOR]

In this work, a biosensor based on a structurally chiral medium (SCM) under the effect of a low-frequency electric field has been designed to detect blood hemoglobin. The introduced structure is irradiated with a circularly polarized light under an electro-optical Pockels effect. A photonic band gap is observed in the transmission spectrum of the right-handed circularly polarized waves, which indicates the circular Bragg phenomenon. The sensor consists of a sample layer sandwiched between two identical SCMs. Sensor performance is evaluated using the transfer matrix method (TMM). The results show that the defect mode is sensitive to any change in the refractive index of the defect layer where the defect layer is infiltrated with samples with different concentrations of blood hemoglobin. Also, it is shown that applying a low-frequency electric field increases the sensitivity of the mentioned sensor. It is observed that the sensitivity can be expanded up to 142.66 nm/RIU by changing the various parameters of the SCM.

This paper presents the review of recent progress in photonic crystal fiber (PCF) and its applications. PCF possesses prominent potential for demonstrating various optical devices such as logic gates, combinational circuits, sensors, absorbers, etc. Recent development in PCFs incorporates the deep learning algorithms which deploy new functionalities and enhance the performance capacity in term of accuracy and optimization in comparison to conventional techniques based on Maxwell solver like finite element method (FEM), and plane wave expansion and finite difference time domain (FDTD) method. Thus, this review paper describes the overview of recent development along with historical background of PCFs and rigorous study on deep learning which incorporates neural network and machine learning algorithms like polynomial expansion method, gradient boost, and random forest. [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]

Theoretical calculations and numerical simulations play a crucial role in analyzing material properties and devising effective research strategies. In this study, the photonic band gap (PBG) of polymethyl methacrylate (PMMA) and polystyrene (PS) photonic crystals was successfully predicted using theoretical calculations and numerical simulations. The agreement between the predicted results and the actual reflection peaks reached an impressive level of 99%. Utilizing SEM images, the prediction of reflection peaks in acrylamide (AM)—based photonic hydrogels was conducted using theoretical formulas and Rsoft 2019–Bandsolve software v2019.09. The relationship between the actual reflection peaks and compressive strains in AM-based photonic hydrogels featuring 251 nm PMMA PCs exhibited a remarkable similarity of over 96% with the theoretical and simulated results. In conclusion, an exploration was conducted into the relationship between reflection peaks and compressive strains for AM-based 270 nm PMMA photonic hydrogels, allowing the prediction of the actual reflection peaks under compression. The consistency observed between theoretical/simulated reflection peaks and actual reflection peaks validates the efficacy of this approach in evaluating the optical properties of photonic materials and predicting their responsive effects. This method offers a straightforward and expeditious solution for the design and fabrication of photonic materials. [ABSTRACT FROM AUTHOR]

Based on potassium tantalate niobate (KTN) as a platform, a Lamb wave-generated tunable photonic structure is proposed. A half-micrometer-thick KTN film is perturbed by a GHz Lamb wave disturbance to produce alternate contraction and rarefaction. Considering the elasticity of the plate, the strength of the disturbance is optimized, and the induced strain is calculated. Following the photoelastic relations, the strain-modified optical properties of the medium along the film length are assessed. The spatial optical index distribution over a space of a few micrometers, as induced by elastic disturbance, may open forbidden electromagnetic band gaps. Utilizing the transfer matrix method, the dispersion curves and transmittance of electromagnetic waves are evaluated and analyzed. As a consequence of Lamb disturbance, a photonic band gap lying in the mid-wavelength infrared range is achieved from the KTN slab. To establish the band gap tunability, the effect of Lamb frequency on the range of photonic band gaps is analyzed. The accomplished acoustic-optical phenomenon on the KTN slab may be utilized for mid-wavelength infrared-ranged tunable optical applications. [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.

Quantum Controlled NOT (CNOT) gate is a well known logic gate in the world of quantum computing and data processing from application point of view. Recently, photonic crystal based logic gates have attracted increasing attention from researchers due to their compact size, low power requirement, high speed, simplified design, better confinement and ability for integration in optical network. In this paper, we have designed and simulated all-optical CNOT gate based on two-dimensional photonic crystal composed of hexagonal lattice of silicon (Si) rods arranged in air background. The operation of the proposed structure is based on the phenomenon of interference of light waves. Finite difference time domain and plane wave expansion methods have been used to simulate the proposed structure. We have found the contrast ratios at the output ports are 16.66 dB and 16.02 dB respectively. The response time of the proposed structure is 0.612 ps and can operate at a bit rate of 1.63 Tbps. The proposed structure offers fast response time and high contrast ratios that ensure efficient performance and make it suitable for high speed optical integrated circuits. [ABSTRACT FROM AUTHOR]

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]

The research field of photonic crystals (PhCs) remains active on a global scale. PhCs, which are periodic optical nanostructures with the characteristics of excellent light field confinement and numerous varying degrees of freedom, provide a solid foundation for controlling the movement of light. Periodic variation of the index of refraction in two or three spatial dimensions with a substantial high-to-low ratio generates a number of intriguing phenomena and enables a variety of potential functionalities. Recently, intriguing devices based on PhCs, such as Y-branches, small-diameter bent waveguides, and miniature resonator cavities, have been proposed and extensively utilized. PhC waveguides are considered ideal candidates for a variety of applications, such as in power splitters, logic gates, sensing and communication fields, etc. These exceptional characteristics may facilitate the development of a dense integrated circuit. However, PhC technology is still relatively new and therefore requires additional effort to fully exploit it. This paper reviews the most popular and essential optical components based on PhCs, including power splitters, modulators, polarization maintaining devices, sensors, and lasers, to summarize the most recent developments relating this hot topic. These devices have superior performance and a smaller footprint compared to conventional photonic devices. [ABSTRACT FROM AUTHOR]

In the present study, a photonic crystal fiber with a simple design and low losses in the range of terahertz broadband pulse was designed. The proposed structure of this study consisted of a large central air core arranged by three rings of air holes in a regular hexagonal pattern in a uniform Teflon matrix. The refractive index of Teflon, which was made of polymer, was 1.44. The conduction in this fiber was achieved using photonic band gap (PBG) only for a certain range of non-zero values. The simulation results showed that at the wavelength of 174 µm with a central hole diameter of 2.9Ʌ (Ʌ = 300 µm), the lowest confinement losses equal to 0.2 dB/m occurred and the dispersion parameter was 1.2 ps/nm km. [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]

This paper reviews the PBG theory, the crystallization of monodisperse colloidal solutions and a method which enables to build three-dimensional periodic structures using polystyrene microspheres. Two techniques which increase the refractive index contrast are also described. One is based on the inverse-opal method and the other on the incorporation of silver between the interstices of a colloidal crystal. [ABSTRACT FROM AUTHOR]

In this study, a new design of 1 x 2 photonic crystal beam splitters is proposed to achieve symmetrically higher power splitting. Two different splitters based on hybrid couplers made from silicon (Si) and poly(methyl methacrylate) (PMMA) materials were studied. One splitter had two outputs, and the other had four outputs. The PMMA temperature was varied from 0 °C to 130 °C to enhance the optical performance of the proposed splitters. The power intensity and photonic band gap (PBG) values were numerically investigated using the finite-difference time-domain (FDTD) and plane wave expansion (PWE) methods. The effect of temperature on these values was also studied to obtain the optimal conditions for high efficiency. The efficiency values were satisfactory. They could reach 49.9 % from the two output ports at a temperature of 80 °C. [ABSTRACT FROM AUTHOR]

We investigated the properties of linear and circular dichroisms of cholesteric liquid crystal layer in external static magnetic field directed along helix axis. We showed that when the direction of light propagation and the direction of external magnetic field coincide, increasing the latter magnitude leads to a decrease in the linear dichroism, whereas when these directions are opposite, increasing the external magnetic field (${B_{ext}}$ B e x t ) magnitude leads an increase in the linear dichroism. The presence of external magnetic field leads to the shift of circular dichroism curves both along wavelength axis and along dichroism axis. Then, we investigated the peculiarities of dichroism dependencies on ${B_{ext}}$ B e x t for different wavelengths of incident light. We compared the dependence of circular dichroism on ${B_{ext}}$ B e x t for a magnetically active cholesteric liquid crystal layer and an isotropic magnetically active layer and showed that while these dependencies are similar for wavelengths away from the photonic band gap, diffraction significantly affects these dependencies for wavelengths near and inside the photonic band gap. We investigated the evolution of spectra of linear and circular dichroisms at the change in ${B_{ext}}$ B e x t , too. The results obtained can find application in the design of innovative polarised optoelectronic devices. [ABSTRACT FROM AUTHOR]

Bound states in the continuum (BICs) garnered significant research interest in the field of sensors due to their exceptionally high-quality factors. However, the wide-band continuum in BICs are noise to the bound states, and it is difficult to control and filter. Therefore, we constructed a top-bottom symmetric cavity containing three high permittivity rectangular columns. The cavity supports a symmetry-protected (SP) superbound state (SBS) mode and an accidental (AC) SBS mode within the bandgap. With a period size of 5 × 15, the bandgap effectively filters out the continuum, allowing only the bound states to exist. This configuration enabled us to achieve a high signal-to-noise ratio and a wide free-spectral-range. The AC SBS and the SP SBS can be converted into quasi-SBS by adjusting different parameters. Consequently, the cavity can function as a single-band sensor or a dual-band sensor. The achieved bulk sensitivity was 38 µm/RIU in terahertz wave band, and a record-high FOM reached 2.8 × 108 RIU−1. The effect of fabrication error on the performance for sensor application was also discussed, showing that the application was feasible. Moreover, for experimental realization, a 3D schematic was presented. These achievements pave the way for compact, high-sensitivity biosensing, multi-wavelength sensing, and other promising applications. [ABSTRACT FROM AUTHOR]

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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, a wide bandwidth (20 GHz) and small sized (200 × 200 × 50 µm3) terahertz (THz) square graphene ribbon antenna using Photonic Band Gap (PBG) substrate are investigated in the 0.6–0.8 THz band. The proposed antenna consists of graphene as radiating patch mounted on four types of ground plane. The important aim of this work is to eliminate the second resonance frequency by utilize a several types of ground plane and keep a single frequency by improving the performance of the proposed antenna. The effect of change ground plane on the performance of antenna is compared, in terms of reflection coefficient, bandwidth, directivity and radiation pattern. The antenna has achieved good gain (7.62 dB) and good directivity (6.38 dB) in comparison to work reported in the literature. [ABSTRACT FROM AUTHOR]

In this study, two-dimensional photonic structures (triangular, square, and honeycomb) are used to realise chip-to-chip communications in two ways. The transportation of signals from one chip to another is quite plausible because the lower potential value changes from 0.55 to 1.0 V. In this case, the operational mechanisms cope with the investigation of the photonic band gap analysis of the proposed crystal, which is prepared using the plane wave expansion technique. Apart from this, various types of losses such as propagation, diffraction, absorption, and scattering have also been investigated to realise the different efficiencies of the structures. These communications are envisaged through a laser diode (transmitter), photonic crystal structure (waveguide), and photo diode (receiver), which in turn act as a photonic integrated circuit. Here, 0.55 V, 0.62 V, 0.65 V, 0.68 V, 0.72 V, 0.75 V, 0.78 V, 0.8 V, 0.83 V, 0.86 V, 0.88 V, 0.90 V, 0.91 V, 0.92 V, 0.94 V, 0.95 V, 0.97 V, 0.98 V, and 1.0 V have been employed to realise an efficient optical VLSI device. The output result indicates that no loss is accomplished with the photonic integrated circuit, which infers efficient circuits for the exchange of signals from one electronic chip to another. [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]

In this article, taking into consideration the exceptional technological properties of a unique 2-D material, namely Graphene, we are envisioning its usage as the structure material of a non-back-gated re-programmable switching device. The proposed topology is analyzed in depth, not only by verifying its operation and re-programmability as a 2-input XOR, 3-input XOR and 3-input Majority gate, but also by examining its computing performance in terms of area, delay and power dissipation. More specifically, we are utilizing L-shaped Graphene Nanoribbons (GNRs) to develop comb-shaped Graphene based switching devices. These devices are in position with effective programming through biasing to design any combinatorial circuit as resulting from the aforementioned universal set of Boolean gates. The resulting figures of merit regarding the area with a universal footprint of $\text{2.53 nm}^{2}$ for every gate independently of the number of inputs, the propagation delay with $2.05\times {10^{-2}}\;\text{ps}$ and, last but not least, the power dissipation with only $\text{10.204 nW}$ for the gates with greater number of inputs, are quite encouraging and promising. Moreover, the ability of the proposed topology to pave the way towards the implementation of basic circuits has been further investigated, by demonstrating an example of a 1-bit full adder cell and its sufficient operation arriving from the corresponding successful SPICE simulation results. [ABSTRACT FROM AUTHOR]

Most of today's computing technology employs Si-based CMOS-transistors and the associated CMOS logic-family. In contrast, alternate devices (like spin valve, spin diode, etc.) and the other logic family (like diode logic) present a better alternative with enhanced performance advantages such as high speed, smaller size, and enhanced power efficiency. Moreover, 2D materials due to their ultimate thinness and unique spin-dependent properties have successfully attracted the research interest for future nano-spintronic devices. Here, we have first studied the impact of fluorination on zigzag/armchair silicene nanoribbon and modeled the most favorable half-fluorinated zigzag silicene nanoribbon-based spin diode. The spin-dependent transport characteristics such as I-V curve and transmission spectrum were calculated by employing density functional theory (DFT) and non-equilibrium Greens function (NEGF) formalism. The origin of the obtained transport characteristics is elucidated by using the spin-dependent transmission spectrum and the density of states (DOS) of electrodes. The device shows 100% spin filtering efficiency, a large rectification ratio of 1.6 × 1023, and large magnetoresistance of 1.5 × 1025. A comparison of the modeled device with the state of art devices is also drawn to evaluate its performance. Furthermore, a novel spin diode logic NOT and universal NAND operations were realized, which suggests the implementation of a complete spin diode logic family-based architecture. [ABSTRACT FROM AUTHOR]

Regardless of the fact that the confirmed Power Conversion Efficiency (PCE) of kesterite materials for photovoltaic cells is lower than that of other chalcogenide materials, there is still sign of improvement due to their high absorption rate, flexibility to have a tunable bandgap, abundance in nature, and so on.The primary objectives of this study was to assess the combined utilisation of quantum dots and quantum wells in kesterite material. This was achieved through three key approaches: firstly, by altering the quantity of quantum dots and wells present in the nanostructure; secondly, by modifying the composition of the dots and well material through adjustments in the Sulphur and Selenium ratio of CZTSSe. The third aspect to consider is the analysis of the effect of changes in operating temperature on high-performing nanostructures, building upon the information gathered from the previous two processes. Electrical properties such as PCE, $ V_{oc}$ , $ J_{sc}$ , and IV curve have been analyzed so that the performance of the hybrid structure can be examined. A quantum well and a quantum dot layer are both present in the p-i-n structure. The quantum dot layer is composed of ten quantum dots placed in an array. The effects of quantum dot thickness (5 and 10 nm) were also investigated. According to the findings, as few as three quantum dot layers and three quantum wells resulted in a 21% PCE. By varying the operating temperature between 250 K to 500 K, the temperature dependency of high-PCE structures was examined. [ABSTRACT FROM AUTHOR]

We perform first-principles calculations, to investigate the effect of doping of metal dopants (silver, gold, aluminum, and copper) on the electronic, structural, and optical properties of strontium titanate SrTiO3. We further explore the impact of varying strains (compressive and tensile) on the optical and electronic properties of pristine and doped SrTiO3. Our results suggest that the undoped SrTiO3 exhibit a wide bandgap of 2.94 eV with high optical absorption only in the ultraviolet (UV) region. On doping the SrTiO3 by metal dopants, the bandgap is significantly narrowed and most of the absorption peaks are found to shift towards the lower energies (red-shift). Subsequently, the absorption is enhanced in the visible region (∼380 to 800 nm) of the optical spectrum. The decrease in the bandgap is highest for the dopant Cu. Further, on the application of the biaxial strain (tensile and compressive) on the doped-SrTiO3, the optical absorption is enhanced in the visible region, particularly for the high compressive strain of 20%. The calculated refractive index and dielectric function for all the structures of SrTiO3 are found to follow the trend of absorption. The enhanced absorption in the desired visible region through doping and strain may find prospective applications in the fabrication of photovoltaic, optoelectronic, and solar devices. [ABSTRACT FROM AUTHOR]