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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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

Optical decoders are essentially required components for creating all-optical digital systems used in optical data processing and logical operations. In this paper, a novel structure of a 2*4 optical decoder is proposed for design using a two-dimensional photonic crystal (2D PhC). The proposed decoder is based on silicon rod photonic crystals with four output ports, two input ports, and a biasing port. For logic, 0 and 1 are introduced based on the maximum, and minimum power levels (0.1Pin and 0.37Pin), where Pin is the input power. Analyze of 2*4 decoder presented here is done using the Finite Difference Time Domain and Plane Wave Expansion methods—which provide the result of all functional parameter simulation and band structure of the lattice, respectively. The results show that the proposed 2*4 optical decoder with optimized functional parameters is suitable for all-optical information processing in future. [ABSTRACT FROM AUTHOR]

In the present manuscript, theoretical investigation of interface modes at the interface of two isotropic dielectric photonic crystals is performed. For both transverse electric ( σ - polarized waves) and transverse magnetic ( π - polarized waves) cases dispersive properties such as dispersion curve, photonic band gap (PBG) shrinking - optical holes and Brewster points are discussed. For the case of σ - polarized waves, interface modes are exhibited which are of prime importance in the present analysis. It is shown that for σ - polarized waves only DD (decaying-decaying) and DE (decaying-extending) type interface modes exist. On the other hand, for the case of π - polarized waves only EE (extending- extending) type interface modes exist which is completely transmitted through the photonic structure. Therefore, depending on the properties of the chosen materials, such photonic structure can seek different applications in the design of sensors, optical filters, optical switches, etc. and it is also suitable to explore the electromagnetic (EM) behaviour at the interface of various media. [ABSTRACT FROM AUTHOR]

Lamb wave's perturbation effect on electromagnetic modes propagating in Y − X lithium niobate slab is theoretically investigated. Rayleigh Lamb dispersion curves are estimated to investigate the behaviour of Lamb waves in micrometer order thick slab. Utilizing the information obtained from dispersion curves, acoustic displacement patterns and strain generated along the plate are evaluated. The modification caused to the refractive index of lithium niobate due to Lamb wave induced strain with photoelastic effect is determined. Further, the features of acoustically modified refractive index are examined using the transfer matrix method. It is found that an acoustically modified refractive index offers forbidden electromagnetic band gaps that can be adjusted by tuning the frequency of Lamb waves and by changing the incidence angle of electromagnetic waves. Hence proposed structure is used as a dynamically tunable photonic crystal for various applications like optical filters and optical switches. [ABSTRACT FROM AUTHOR]

In this study, an antenna is proposed that operates at THz spectrum for sixth generation (6G) short-range future wireless communications. A modified photonic band gap (MPBG) substrate is employed to design an octagonal ring shaped microstrip patch antenna with wideband and high gain properties. Unlike the conventional photonic band gap (PBG) form, the proposed MPBG substrate structure is created by variable sized cylindrical air holes. The radii of each air cylinder in the row is determined with the help of particle swarm optimization (PSO) algorithm, where the goal is set to achieve the highest gain and impedance bandwidth (11 = -10) possible. The simulation results of the antennas that are built on 1) non-PBG, 2) conventional PBG and 3) the proposed MPBG substrate structures are compared. It is observed that the radiation performance is most enhanced by implementing MPBG structure. In comparison to the antenna without PBG, the reported MPBG structure offers almost 300% gain and 11% bandwidth improvement. To summarize, the designed antenna with its proposed MPBG substrate structure achieves an excellent radiation performance within a wide operating bandwidth. [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]

Amorphous arsenic trisulphide (As 2 S 3) chalcogenide glass is widely used in photonics and optoelectronics due to its wide transparency in the infrared spectral range, its high linear refractive index (n As2S3 = 2.42), which can be significantly modified by light with a suitable wavelength, and its important optical nonlinearity. In this work, we report the design of an all-optical tunable two-dimensional photonic crystal in a geometry which consists in a hexagonal lattice of holes patterned in As 2 S 3 film with the aim to exhibit photonic band gap in the near infrared domain. We numerically investigated the possibility to all-optically tune the photonic band gap of an already patterned photonic crystal in As 2 S 3 modifying only its refractive index by illumination with light of wavelength λ at the band gap energy (λ = 514.5 nm) or shorter, without affecting the lattice geometry. The influence of the variation of As 2 S 3 refractive index (Δ n) on the spectral position of the band gap and on its width has been determined for the light-induced modification of Δ n up to the value of 0.09. For this value of Δ n, a shift of almost 50 nm of the central wavelength of the photonic band gap has been obtained. These results are of great interest in the field of photonics offering a versatile solution to fabricate all-optical tunable photonic crystals in any optical material whose refractive index can be modified by light. [ABSTRACT FROM AUTHOR]

Gold nanoclusters (AuNCs) are an intensely pursued class of fluorophores with excellent biocompatibility, high water solubility, and ease of further conjugation. However, their low quantum yield limits their applications, such as ultra‐sensitive chemical or molecular sensing. To address this problem, various strategies have been adopted for augmenting their fluorescence intensity. Herein, we report a facile and scalable approach for the fluorescence enhancement of bovine serum albumin (BSA) capped AuNCs (BSA‐AuNCs) using periodic, close‐packed polystyrene colloidal photonic crystals (CPCs). The slow photon effect at the bandgap edges is utilized for the increased light‐matter interactions and thereby enhancing the fluorescence intensity of the BSA‐AuNCs. Compared to the planar polystyrene control sample, the CPC film yielded a 14‐fold enhancement in fluorescence intensity. Further, we demonstrated the as‐prepared BSA‐AuNCs‐CPC as a solid‐state platform for the highly sensitive and selective fluorescence turn‐off detection of creatinine at nanomolar level. [ABSTRACT FROM AUTHOR]

Power electronics converters operating at elevated temperature usually have degraded performance, such as reduced efficiency, lower noise immunity, and decreased system reliability, compared to those operating at room temperature. Nevertheless, harsh-environment applications, such as deep earth drilling, automotive, avionics, and space exploration, have been utilizing converters in high-temperature environments and are continuously pushing the temperature limits higher and higher with the advances in device technologies and converter design methodologies. This article starts with a literature study to identify the temperature dependence and the temperature limits of individual components. Then, published works about high-temperature converters are examined. Their selection of components is compared. Experimental results are analyzed to reflect on the efficacy of different component selections. Finally, since the latest published high-temperature converter was developed more than five years ago, a 1-kV input, 520-V output, 1-kW, $150$ °C-ambient-temperature-rated dc–dc converter is designed with state-of-the-art devices. Based on the literature review, and the test of the $150$ °C prototype, the main challenges of designing high-temperature power electronics converters are identified and concluded to be time-consuming, difficult, and expensive characterization of components, lack of accurate and computationally efficient models of converters, and optimizing component selection within short development time. [ABSTRACT FROM AUTHOR]

In the present investigation, we have undertaken photoluminescence, UV–Vis absorbance, transmission and polarised light microscopy of the composites of a cholesteric liquid crystal (CLC) doped with quantum dots (QDs). The locally formed QDs clusters may distort the CLC's helix to induce an imperfect planar texture and cause broadening of CLC's photonic band gap. This broadening is accompanied by a change of the wavelength positions of the central and both the long and short band-edges of the photonic band gap as the concentration of the doped QDs increases. A remarkable enhancement in the photoluminescence intensity of CLC materials is observed by doping with QDs. A decrement in the FWHM parameter also supports this increased photoluminescence intensity. The UV absorbance increases for the QDs dispersed CLC material and is followed by a slight red shift when compared to the pure CLC. The optical band gap obtained by the Tauc plot method suggests that the observed optical band gap narrows after the dispersion of QDs into the CLC. The outcome of these investigations proves that the dispersion of QDs in CLC is beneficial and may be useful in liquid crystal displays and other opto-electronic devices, which require less band gap materials. [ABSTRACT FROM AUTHOR]

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

The current communication deals with the investigation of sucrose concentration in aqueous solution using copper-based metamaterial structure at a wavelength of 1550 nm. In this article, 5×5 air holes are engraved on a copper-based metamaterial structure, which contains the different concentration of sucrose in aqueous solution. Further, the present structure manipulates with finite difference time domain (FDTD) technique to compute the sucrose concentration. Moreover, different losses (absorption loss, dispersion loss, propagation loss, and polarization loss) are measured for the same. Nevertheless, similar type of papers have been published, the present paper has a couple of benefits including the method of computation (FDTD) and the output variation (linear ship) with the concentration. Apart from this, the present research shows the error bar, which deals with an accurate measurement. Again a mathematical model is also obtained, which gives the relationship between the sucrose concentration and the output intensity. Further, output results declared that transmitted intensity varies linearly with the concentration of sucrose. Lastly, a feeble error in the commutation proclaims an accurate investigation of sucrose in their aqueous solution with the help of a photonic structure. [ABSTRACT FROM AUTHOR]

This paper proposes a two-dimensional photonic crystal ring resonator for temperature sensing. The sensor structure is based on a hexagonal array of silicon (Si) rods surrounded by air. Its size is 11.5 × 10 μm in X and Z directions, respectively. The detection principle is based on the change of the refractive index of silicon. This variation is due to the change of the applied temperature and shifts in the resonance wavelengths. The finite difference time domain and plane wave expansion methods were used to simulate the light transmission for different temperatures and photonic band gaps. The proposed sensor has a significant performance, a sensitivity of 935 nm/RIU, a calculated quality factor of 135, a merit factor equivalent to 81 RIU−1, and a detection limit of 1.24 × 10–3 RIU. The results are very interesting and show that the sensor is reliable, very compact, and can be integrated into various applications of transduction and detection. [ABSTRACT FROM AUTHOR]

In this work, we have investigated perovskite-based solar cells (PSCs) with seven different organic hole transport layers (HTLs), which include spiro-2,2’,7,7’-Tetr- akis-(N, N-di-4-methoxyphenylamino) −9,9’-spirobifluorene (OMeTAD), poly(triaryl amine) (PTAA), poly (3,3”’-dialkyl- quaterthiophene) (PQT), poly (3, 4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), poly (3-hexylthioph- ene-2,5-diyl) (P3HT), Poly [2-methoxy-5-(2’-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV), and n-Propyl Bromide (nPB). This article reports the impact of several device parameters, such as perovskite layer defect density, and thickness, on the solar cell performance. We examined the device performance for the PSC device architecture, i.e., fluorine-doped tin oxide (FTO)/TiO2/CH3NH3PbI3/HTLs/Au. For this study, numerical simulation has been performed and optimized for optimum absorber layer thickness and defect density. In this study, we report the power conversion efficiency (PCE) with various HTLs, such as 10.01% for MEH-PPV, 13.94% for PEDOT:PSS, 14.75% for P3HT, 15.42% for PQT, 15.74% for NPB, 17.08% for PTAA, and 17.11% for spiro-OMeTAD at an optimized thickness of 300 nm. It is asserted that there is an enhancement in the photovoltaic performance observed while using spiro-OMeTAD and PTAA as HTL. PSC using spiro-OMeTAD as HTL shows exceptional performance compared to other HTLs. Other parameters obtained for PSC using spiro-OMeTAD are ${V}_{OC}$ of 1.10 V, ${J}_{SC}$ of 20.772 mA/cm2, FF of 0.74%, and PCE of 17.11%. The elicited simulation results suggest that spiro-OMeTAD is the most promising candidate for HTL to fabricate low-cost, highly efficient, and low-temperature processed hybrid PSC. [ABSTRACT FROM AUTHOR]

Dirac-source field-effect transistors (DS-FETs) have been proposed as steep-slope transistors for low-power switching. The steep-slope switching of a DS-FET originates from the “low-pass” energy filtering effect of the graphene Dirac source, which requires the number of modes in the graphene source to be lower than the ones in the channel. However, despite the fact that this requirement is not satisfied in a DS-FET with a carbon nanotube (CNT) channel, steep-slope switching has been experimentally demonstrated in such devices. In this article, we propose a mechanism of switching in CNT DS-FETs that is consistent with the small number of modes in a CNT. We argue that the CNT acts as a transverse momentum selector, which effectively introduces a bandgap in the graphene source, and thus, the Klein tunneling in the graphene n-p junction becomes band-to-band tunneling (BTBT). This makes the CNT DS-FET essentially a new type of tunneling field-effect transistor (TFET), which we call momentum-selector TFET (MS-TFET). Moreover, we study the impact of misorientation between graphene and CNT on the performance of a CNT MS-TFET. Finally, we show that scattering may actually be beneficial in such a device and could potentially enhance the on-current of a CNT MS-TFET. [ABSTRACT FROM AUTHOR]

We present a detailed methodology for drift-diffusion (DD) modeling of gain and dark currents in mid-wave infrared (MWIR) and short-wave infrared (SWIR) ${\mathrm {Hg}}_{{1}-{x}}$ CdxTe p-around-n avalanche photodiodes (APDs) based on a comprehensive analysis of experimentally obtained data from three different sets of devices. These devices are fabricated on homogeneous and compositionally-graded films with cadmium composition ranging from ${x}\,\,=0.37$ to 0.45, each with differing geometrical dimensions, and tested at operating temperatures ranging from 140 to 240 K. The temperature, composition, and electric-field dependent impact ionization (ImI) coefficients are calibrated first according to the given experimental gain data. The gain-normalized dark current (GNDC) curve, along with the presumption of electron-only multiplication, is then used to thoroughly understand and model the behavior of diffusion and generation currents. At high biases, the GNDC curve reveals contributions from tunneling, which are classified as either trap-assisted or band-to-band based on their temperature dependence. The tunneling mechanisms are modeled accordingly: trap-assisted tunneling (TAT) is scaled inversely with Shockley–Read–Hall (SRH) lifetime, while band-to-band tunneling (BTBT) is scaled with bandgap, effective mass, and an additional empirical temperature term. Finally, the comprehensive model is applied to all three experimental devices across the operating temperature range with good agreement. [ABSTRACT FROM AUTHOR]

Contact resistance strongly deteriorates the performance of devices based on 2-D materials and their nanostructures, masking their exceptional electronic and transport properties. This work explores the dependence of contact resistance (${R}_{C}$) of graphene nanoribbon (GNR) devices on contact geometry using atomistic quantum transport simulations. The influence and contributions of edge and top contacts and GNR width scaling on ${R}_{C}$ is studied in detail. Metallization effects on the density of states, transmission, and GNR field-effect transistor (GNR FET) driving current are investigated. We show that wider GNRs (~4 nm) exhibit edge-dominated transport and lower ${R}_{C}$ than the ultranarrow GNRs (~0.4 nm) that exhibit much higher contact resistance which is also dependent on the contact area. [ABSTRACT FROM AUTHOR]

We demonstrate nonvolatile and area-efficient ternary content-addressable memories (TCAMs) featuring amorphous indium–gallium–zinc–oxide (a-IGZO) ferroelectric field-effect transistors (FeFETs) with excellent electrical characteristics. An extremely large sensing margin of the TCAM array is achieved due to the large current ON/OFF ratio ($I_{ \mathrm{\scriptscriptstyle ON}}/I_{ \mathrm{\scriptscriptstyle OFF}})$ of the a-IGZO FeFETs. Our HfxZr $_{\text {1-x}}\text{O}$ 2 (HZO)-based a-IGZO FeFETs have a metal–ferroelectric–metal–insulator–semiconductor (MFMIS) structure. By engineering the area ratio of the ferroelectric layer (${A}_{Fe}$) and the metal–oxide–semiconductor layer (${A}_{MOS}$), a large memory window (MW) of 2.9 V is realized. Reliability test results, including retention, endurance, and positive bias temperature instability, show long-term retention of more than ten years and high endurance of 108 cycles. In addition, by scaling the channel length down to 40 nm, ON current of $77 ~\mu \text{A}/ \mu \text{m}$ (${V}_{\mathrm{GS}} - {V}_{\mathrm{TH}}$ = 5 V and ${V}_{\mathrm{DS}}$ = 2 V) and ${I}_{ \mathrm{\scriptscriptstyle ON}} / {I}_{ \mathrm{\scriptscriptstyle OFF}}$ of more than eight orders can be obtained for the ultrascaled a-IGZO FeFETs while maintaining an MW of 2.8 V. [ABSTRACT FROM AUTHOR]

Frenkel pair (FP) formation at HfO2/Ti interface and oxygen vacancy interaction with the filament in HfO2/Ti-based resistive random access memory (ReRAM) are the important mechanisms in the ReRAM operations. In this article, the formation barriers, ${E}_{A}$ , and formation energies of ${V}_{O}/{O}_{i}$ FP across the HfO2/Ti interface with and without preexisting vacancy are calculated using the ab initio tool under zero external electric field. It is found that both the formation barrier and energy can be increased or decreased due to a preexisting oxygen vacancy. The spread of the effect increases inversely with the distance between the FP and the preexisting vacancy. A compact model is then proposed. The parallel migration barrier of an oxygen vacancy at the nearest and the second nearest neighbors (NNs) of a filament is also studied. It is found that the second NN has the lowest barrier due to its ability to retain a +2 charge state. The merging and dissolution of an oxygen vacancy with a filament (equivalent to perpendicular migration) is found to have a similar behavior that +2 states enhance the interaction. It is found that the fourfold coordinated oxygens (4C) and threefold coordinated oxygens (3C) filaments behave similarly during dissolution. However, 4C and 3C filaments prefer merging with 4C and 3C vacancy, respectively. The barrier of merging a +2 4C vacancy with a 4C filament is only 0.56 eV. The data and model obtained from this study may be used to implement device-level simulators, such as kinetic Monte Carlo (KMC) simulators, for ReRAM. [ABSTRACT FROM AUTHOR]

All-optical NAND and NOR logical gates based on two-dimensional photonic crystals have been designed and analyzed in this research. A hole in the silicon substrate was created to design the desired gates, and the light emission analysis was performed using the FDTD numerical method. Most of the circuits that have been designed so far based on photonic crystals have included dielectric rods in the airfield. This research uses a hole in the silicon substrate, which is more suitable for fabrication. The proposed structure is created symmetrically using a small photonic crystal. The simulation results show that this small structure can be used as two NAND and NOR gates, which have a suitable power difference in the upper and lower logic states. Therefore, the proposed structure is suitable for precise logic circuits and high transmission speed. Due to the simplicity of structure and small size, the output stable time for NAND and NOR gates are 0.9 ps and 0.67 ps, respectively, indicating the gates' low delay time. Also, the value of the contrast ratio for NAND and NOR gates is 7.26 dB and 6.35 dB, respectively, which indicates the appropriate power difference in the upper and lower logic states. [ABSTRACT FROM AUTHOR]

The recent progress in III-nitride tunnel junction (TJ) contacts for optoelectronic devices is summarized in this review paper. Due to the rapid developments of various III-nitride based optoelectronic devices for different emerging applications, TJs are of interest for these devices to achieve more efficient device performance. This review paper first briefly describes the working principles of TJs and the advantages of employing TJs in optoelectronic devices. The significant advancements in III-nitride TJs realized by metalorganic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) are addressed, as well as their TJ device performances. Lastly, the critical challenges for employing III-nitride TJs in wide bandgap ultraviolet (UV) light emitters are discussed for future investigations. [ABSTRACT FROM AUTHOR]

Gallium phosphide (GaP) is an important optical material due to its visible wavelength band gap and high refractive index. However, the bandgap of the thermodynamically stable zinc blende GaP is indirect, but wurtzite (WZ) structure GaP is direct bandgap. In this work, we demonstrate high-quality and dense GaP vertical nanopillar (NP) array directly on Si (111) substrates through selective area epitaxy (SAE) by MOCVD for the first time, through systemic studies of the effect of TMGa flow rate, growth temperature, and V/III ratio. Uniform GaP NPs are grown over a patterned $400\,\,\mu \text{m}\,\,\times 400\,\,\mu \text{m}$ area with 97.5% yield. Arrays of GaP vertical p-i-n NP diodes are demonstrated with a ideality factor and rectification ratio of 3.7 and 103, respectively. With the high yield of hexagonal structure and electrically proven device quality of GaP NPs through this growth method, this work represents a significant step in achieving GaP NP based optoelectronic devices, such as micro-LEDs emitting in the green wavelength range. [ABSTRACT FROM AUTHOR]

We report AlInAsSb separate absorption, charge, and multiplication (SACM) avalanche photodiodes with a >3- $\mu \text{m}$ optical cutoff, operating at 240 K. Gain and dark current performance further improve with reduced temperature. 65% external quantum efficiency at 2- $\mu \text{m}$ is achieved without anti-reflection enhancement. [ABSTRACT FROM AUTHOR]

We report on a mid-wavelength (MW) type II superlattice (T2SL) photodetector using Ga-free InAs/InAsSb SL structure. X-ray diffraction (XRD) measurements indicate that the strained SL material is of very high quality. It is demonstrated that the background limited performance (BLIP) temperature of the detector is above 160 K and the dark current is dominated by the diffusion mechanism when temperature is above 160 K. At 77, 160, and 280 K, the 50% cutoff wavelength of the detector is 4.54, 4.89, and 5.56 $\mu \text{m}$ , respectively. The responsivity at the peak wavelength is 2.13 A/W at 77 K and is 2.16 A/W at 160 K. We also extract the Varshni parameters of the SL structure. The results indicate that the Ga-free SL structure is similar to InAs bulk material in terms of the Varshni parameters. [ABSTRACT FROM AUTHOR]

The cross-sectional scaling-induced electronic property variations of the Ge and Si nanowires are studied numerically. After removing extra atoms from bulk materials to build the nanowires, not only the lateral quantum confinement is enhanced, but also the cross-sectional size will expand due to the breaking of the intrinsic strain balance. Compared with Si, the strain release-induced size expansion is more obvious in the Ge nanowires, shrinking the bandgaps and thus providing another bandgap modulation direction relative to the quantum confinement. At specific sizes, the strain release effect dominates the modulation and reduces the bandgaps of Ge nanowires even below the bulk value, while the reductions in Si nanowires are negligible, enlarging the band offsets of their heterostructures. As an application, the Ge/Si heterostructure tunnel FET (TFET) is designed and the TCAD simulation reveals a subthreshold swing (SS) of 13.8 mV/dec and an ON-state current of $93 ~\mu \text{A}/\mu \text{m}$ , three orders of magnitude larger than that using the bulk materials. [ABSTRACT FROM AUTHOR]

Conventional field-effect transistors (FETs) based on silicon downscaling are approaching physical limits, and thus, it is urgent to explore additional novel solutions to address this issue. The 2-D semiconductors have unique advantages as the channel material and provide a promising prospect for high-performance FETs in the post-Moore era. In this work, a new 2-D semiconductor, monolayer BeN2, is studied for the FET performance limits through first-principle quantum-transport simulations. Monolayer BeN2 exhibits a graphene-like planar structure with a direct bandgap of 1.3 eV. Transfer characteristics of sub-10-nm BeN2 FETs are thoroughly assessed through scaling gate length. In particular, 2-D BeN2 FETs with 10-nm gate present the ultrahigh ON-state current above $4500\,\, \mu \text{A}/\mu \text{m}$ for high-performance applications. Also, we realize the significant reduction of gate length (only 2.5 nm) against the International Technology Roadmap for Semiconductors (ITRS) requirements through introducing underlap structures. In addition, the performance of single devices based on monolayer BeN2 is evaluated and compared with some of the recently proposed 2-D devices. [ABSTRACT FROM AUTHOR]

Detectivity is the most key parameter in weak-signal photodetection, which depends on high photoresponse and low noise simultaneously. In this work, metal–semiconductor–metal solar-blind UV detectors with internal gain were fabricated based on high resistant and a certain oxygen vacancy density Ga2O3 thin films. Electrical measurements and electric field simulation indicated that thickening the active layer is helpful for high responsivity. The gain is dominated by the tunneling effect in high electric field under the electrodes. A high photoresponse of 371 A/W and a normalized detectivity up to $6.6\times10$ 16 Jones were obtained. [ABSTRACT FROM AUTHOR]

In this work, we report the photodetector properties of a vertically stacked heterostructure based on topological insulator Sb2Te3/n-Si. The high-quality Sb2Te3 thin films were grown on an n-Si substrate by the metal–organic chemical vapor deposition (MOCVD) technique. The fabricated Sb2Te3/n-Si heterostructure devices promise to work as an excellent rectification diode with an excellent rectification ratio (RR) (351.4 at ±3 V), under dark condition. The device shows remarkable photoresponse at a broad spectral near-infrared range of between 700 and 1100 nm. The maximum responsivity and detectivity of Sb2Te3/n-Si heterojunction diode 1600 mA/W and $7.48\times10$ 10 Jones $\vphantom {^{\int }}$ (at +3 V) were observed at 900-nm wavelength of incident light. The electronic and optical properties of the Sb2Te3 are evaluated using first-principle calculations based on density functional theory (DFT). The bandgap of Sb2Te3 was found to be 0.12 eV. The optical properties of Sb2Te3 were calculated based on DFT and random phase approximation. The absorption coefficient shows that Sb2Te3 absorbed the light in a broadband spectral region and maximum absorption at 905 nm, which is in good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

In Part I of this article, we discussed the basic operation of 2-D Dirac-source field-effect transistors (DS-FETs) and studied the impact of key device parameters on the device performance. In this article, we continue to study the impact of nonidealities on the performance of DS-FETs, such as graphene disorder and rethermalization, as well as ways to mitigate them. In addition, we study the performance improvement by introducing a bandgap in the graphene source. Finally, we benchmark the performance of DS-FETs for different channel materials, providing a guide for the proper choice of material for 2-D DS-FETs. [ABSTRACT FROM AUTHOR]

The formamidinium lead triiodide (FAPbI3)-based perovskite solar cell (FPSC) is perceived as a potential replacement of conventionally exploited methylammonium lead triiodide (MAPbI3)-based PSC owing to its better stability. In this work, we explore the possibility of utilizing molybdenum disulfide (MoS2) as a prospective replacement of conventional titanium dioxide (TiO2) (requires high processing temperature) as an electron transport layer (ETL) in FPSC using SCAPS-1D. The results are quantitatively compared in terms of the performance metrics of simulated baseline models. Furthermore, the performance variations are also compared with respect to varying absorber layer defect density. Moreover, the reproducibility aspect of cells is compared with respect to varying carrier mobility of the absorber layer. We observe an outstanding improvement in efficiency and reproducibility of FPSCs with MoS2 as ETL. The results highlight the vitality of ETL material properties toward efficiency and reproducibility enhancement of FPSCs. These findings serve as an important benchmark for improving the commercialization prospects of FPSCs. [ABSTRACT FROM AUTHOR]

In a layered structure containing nano-scale layers, we have presented the possibility of increasing the wave transmission in the visible region by adding the top and bottom cap layers. It is found that, the structure containing both the top and bottom cap layers (S3) yields larger transmittance than the structures S1 without any cap or S2 just with one cap layer. The maximum transmittance in the visible range can be increased from 33% to 67%. In addition, for the TE mode (the TM mode) the maximum value of transmission in the S1 and S2 structures occurs at angles close to normal incidence while in the S3 multilayer it happens around 1 rad, that is, the behavior of the TE mode is the opposite of the TM mode. Also, when the incident angle varies, the band edges experience a blue shift. The amount of TE shift is more pronounced than TM one. [ABSTRACT FROM AUTHOR]

Achieving broadband angular selectivity has been attracting much interest from both scientists and engineers in recent years. Previous experimental demonstrations have been limited to the $p$ -polarized incidence. Here, we propose a universal approach to achieve polarization-independent broadband angular selectivity by introducing electrically and magnetically anisotropic diamagnetic medium into multiple 1-D photonic crystal stacks. Such stacks have a broadband angular photonic bandgap for both $s$ - and $p$ -polarized waves. The anisotropic diamagnetic medium is artificially constructed with periodically arranged close metallic ring arrays, which exhibits a negligible frequency dispersion in an ultrawide band. As a proof of principle, one stack of photonic structures for the normal-incidence-selective case is fabricated and measured in the microwave region. The proposed approach is simple, robust, and scalable from near-zero frequencies to terahertz frequencies, showing promising practical applications such as spatial filters and anti-jamming communications. [ABSTRACT FROM AUTHOR]

In this study, we investigated the sensing capabilities of 1D defective photonic crystal designs composed of single and double defect layers. These structures can detect and distinguish minor refractive index changes of various organic samples infiltrated one by one into defect layer regions of the respective designs. We have used the standard transfer matrix method to analyze the transmission properties of both structures at normal incidence. The normal incidence has been chosen to overcome the experimental difficulties associated with oblique incidence. The performance of the proposed designs has been examined by measuring the shift in the position of the defect modes inside PBGs of respective structures depending upon the change in the refractive index of various organic solvents, called samples. We can also find adulteration in the organic samples by comparing the observed data with the experimentally available standard data of pure organic samples. Moreover, double defect photonic structure possesses pair of two defect modes inside PBG. These pair of defect modes are located on either side of bandgap edges that cannot be found in 1D defective PCs composed of a single defect. This intriguing property of double defect PC structure is due to the quasi Fabry–Perot cavity nature of the structure. Finally, we have compared sensing and detection features of both the designs made up of single and double defect photonic structures. It has been noticed that the double defect photonic structure also improves the transmittance of defect peak to unity compared to the single defect photonic structure. Moreover, the FWHM of two pairs of defect modes in double defect PC are opposite in nature. This remarkable feature of double defect photonic design may be very useful for improving the performance of photonic bio-sensors. It may be very helpful for designing some advanced bio-sensing designs whose defect mode properties are mirror image in nature. [ABSTRACT FROM AUTHOR]