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Perovskite solar cells (PSCs) have gained a lot of attention due to their high power conversion efficiency (PCE), low-cost materials, and simple manufacturing process. These cells can be improved further by using photonic crystals (PCs) which can increase light absorption. A PC-based perovskite solar cell was designed and simulated in this study using FDTD and CHARGE solvers of the Lumerical software, and its components showed better values compared to other solar cell structures. The study investigated the effect of a two-dimensional PC structure on the solar cell's light absorption. The materials used as photonic crystals were perovskite/rutile TiO2 and perovskite/InAs, and various radii and lattice constants were examined. A comparison between each type of PC with the flat structure was conducted. The simulation results indicate that the most efficient structure was found to be the perovskite/InAs structure with a radius of 40 nm and a lattice constant of 200 nm, resulting in an improvement in the performance of the perovskite solar cell. The flat solar cell structure exhibited a short-circuit current of 24.01 mA/cm2 and an efficiency of 17.34%. However, by adding a rutile TiO2 photonic crystal structure, the short circuit current and efficiency increased to 27.12 mA/cm2 and 19.94%, respectively. The efficiency and short circuit current could be further improved by adding an InAs photonic crystal structure, resulting in values of 20.97% and 28.03 mA/cm2, respectively. The improved performance of PC-based perovskite solar cells compared to PSC was due to the slow photon effect that occurred around the photonic bandgap, causing light to be trapped, and resulting in more electron-hole pairs being produced. In summary, this study demonstrates the potential to improve the performance of perovskite solar cells by utilizing photonic crystals. [ABSTRACT FROM AUTHOR]

In this article, we propose a one-dimensional photonic crystal (1D-PhC) biosensor design to detect water-borne bacteria such as Shigella, Vibrio cholera, Salmonella, and E. coli. The theoretical reflectance spectrum of a 1D-PhC and the sensitivity of types of bacteria such as Shigella flexneri, Salmonella, E. coli, and Vibrios cholera are investigated by using the transfer matrix method and MATLAB software. The impact of incident angle and central wavelength on the performance and sensitivity of biosensors are studied. The suggested sensor's sensing process is dependent on variations in the refractive indices of different species of bacteria. The variation in the central wavelength, angle of incidence, the sensitivity of the proposed structure, and other parameters such as full width at half maximum, quality factor, damping ratio, and detection limit can be enhanced. The obtained average sensitivity of our design has a value of 4073 nm/RIU at optimum conditions of defect layer thickness and incident angle. Also, the proposed biosensor design exhibits a high quality factor value of 10996.2165 and a low detection limit value of 0.44607 × 10 - 5 RIU. [ABSTRACT FROM AUTHOR]

In this work, an all-optical compact 2*1 multiplexer gate based on two-dimensional photonic crystals is presented. The structure is made of silicon rods (which are formed in the eight shaped (8) waveguide) in the background of air. The proposed multiplexer is designed based on only linear materials to overcome low gain and nonlinearity difficulties. The functionality of the multiplexer is fulfilled by considering the interference and scattering effects of silicon defect rods situated in the structure. The performance of the presented structure is studied by considering the photonic band gap, field distribution and transmitted power spectra. Plane wave expansion (PWE) and finite-difference-time-domain (FDTD) methods are utilized for extracting the PBG and field distribution diagrams. The dimension (116.64 μm2), contrast ratio (21.39 dB), rise time (0.8 ps) and bitrate (0.312 Tbit/s) are the remarkable specifications of the proposed multiplexer. In other words, compatibility and integrability are the main advantages of the presented structure. As a result, the proposed 2*1 multiplexer can be considered as an appropriate candidate in optical circuits (optical networking and optical signal processing). [ABSTRACT FROM AUTHOR]

In this article, a two-dimensional photonic crystal-based XOR gate is designed and simulated. For this purpose, an initial two-dimensional photonic crystal structure is chosen and waveguides are created for inputs and outputs. Then, defect rods are selected so that the obtained outputs are approximately consistent with the XOR gate truth table. After that, we will be looking for the best output so that the highest optical power is created for logic 1 and the lowest power in the logical state of 0. For this reason, the simulation is performed for four defect rods and the output is obtained for different the radius of the rods. Then, using the K-Nearest Neighbors algorithm, which is a machine learning algorithm, the best output for logic 0 and also for logic 1 is obtained. The results show that the designed logic gate has high output power in logic 1 and very low power in the logic 0 state. [ABSTRACT FROM AUTHOR]

Topological charges of nodal lines in a multigap system are represented by non-Abelian numbers, and the Euler class, a topological invariant, can be used to explain their topological phase transitions, such as pair-annihilation of nodal lines. Up until now, no discussion of phase transitions of nodal lines in photonic crystals using the Euler class has been reported, despite the fact that the Euler class and topological phase transition have recently been addressed in metallic or acoustic crystals. Here, we show how the deformation of a photonic crystal causes topological phase transitions in the nodal lines, and the Euler class can be used to theoretically predict the nodal lines' stability based on the non-Abelian topological charge theory. Specifically, by manipulating the separation between the two single diamond structures and the extent of structural distortion, we numerically demonstrate the topological transition of nodal lines, e.g., from nodal lines to nodal rings. We then demonstrate that the range of surface states is strongly influenced by the topological phase transition of nodal lines. Moreover, the Zak phase was used to explain the surface states' existence. [ABSTRACT FROM AUTHOR]

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In this paper, a novel interference-based nanostructure was designed and simulated to realize an all-optical 2-bit reversible comparator by employing a novel technique. The plane wave expansion (PWE) method was adopted to analyze the encoder design and frequency modes. Aside from downsizing, the finite-difference time-domain (FDTD) method was utilized for the simulation and numerical analysis of the design proposed herein. An ultra-compact nanostructure with a 129.8 μm2 footprint was utilized for the all-optical 2-bit reversible comparator. One of the noteworthy characteristics of the proposed nanostructure was its excellent contrast ratio (i.e., 13.8 dB) in comparison to other nanostructures. The bitrate and delay time in this nanostructure were 3.33 Tb/s and 300 fs, respectively. Based on the findings of the simulations conducted at a central wavelength of 1.55 μm, it is recommended to employ the nanostructure proposed herein during the third telecom window. A photonic crystal nano-resonator was utilized to design the high-performance all-optical 2-bit reversible comparator, which may also be employed in integrated optical circuits (IOCs).

This comprehensive review investigates the diverse landscape of blood component detection through the one-dimensional, two-dimensional, and photonic crystal fiber biosensors. Each biosensor, dedicated to specific blood components, is scrutinized in detail, with a focus on key parameters such as Quality Factor (Q) coefficient Loss, Figure of Merit (FOM), and Detection Limit (DL). The study discerns notable advancements in sensitivity and confinement loss within the realm of photonic crystal fiber sensors, attributing these improvements to recent structural modifications. The findings contribute valuable insights into the state-of-the-art techniques employed in blood component detection, paving the way for enhanced biosensor technologies in biomedical applications.

The primary concern addressed in this article is the inherent difficulty in creating antennas capable of effectively operating across a range of frequency bands within the terahertz (THz) spectrum. Conventional antenna designs often fall short in terms of delivering the required bandwidth and power for such applications. To mitigate this problem, we present a technique that uses photonic crystals integrated into the antenna design to generate photonic band gaps (PBG) with the graphene loaded in the THz band. So, the purpose was to find the optimal multiband antenna that can function across 1.13 and 0.65 THz. Simulations were conducted for rectangular patch antennas using different types of substrates, which included homogeneous, periodic, and aperiodic photonic crystal substrates, and by using a graphene load, simulations were carried out. Multiple sets of air holes (rectangular and cylindrical) were punched into the polyimide substrate of each modified photonic crystal substrate, and the load graphene was placed in the patch. The anticipated multiband antenna design has successfully achieved impressive performance metrics, including a minimal reflection coefficient of −36.8 dB and −41.812 dB, a substantial bandwidth of 25 GHz, and 110 GHz at 0.65 THz and 1.13 THz, respectively. Additionally, the design boasts a gain of 6.44 dBi, 9.45 dBi, and a remarkable radiation efficiency of 75.12 % and 80.03 %, respectively, with a VSWR

A method for separating clean plates of epicuticular wax has been proposed. The use of water, which can penetrate deeply into wax structures under the influence of van der Waals forces and expand upon freezing, allows to quickly obtain uncontaminated wax plates with a native structure without any third-party chemical impurities. Using scanning electron microscopy, images of blue spruce (Picea pungens Engelm.) needle wax were obtained. Its morphological and structural characteristics have been determined. A distinctive feature is the presence of wax nanotubules with a characteristic diameter of ~150 nm and a length of 3–5 μm. Nanotubes lie on top of each other in stacks, forming a one-dimensional long-period lattice. Microscopic observations of the wax were made in reflected and transmitted light. It has been shown that the coating of blue spruce needles consists of microparticles of wax with a structural color. In a wide spectral range, individual particles change color from blue to red, as a result, large conglomerates of particles are white. Fluorescence spectra of needles with native wax cover and the same needles after wax removal were obtained. When comparing the width of fluorescence lines at half-height of blue spruce needles with and without wax, the influence of the wax layer on the lifetime of excited electrons in photosystem II was revealed, thereby establishing a connection between the wax cover and the process of photosynthesis. Using the matrix transfer method, transmission spectra were calculated for a lattice similar to a waxy structure, a chloroplast, and a combination of a waxy structure with a chloroplast. In the latter version, the long-wave zone of selective reflection is much wider than in individual cases. When examining a structure containing a chloroplast and epicuticular wax, there is a slight splitting of the stop zone, as if there were a defect, which contributes to a high concentration of energy at the site of splitting. Due to an increase in energy concentration, the density of photonic states at the corresponding wavelengths increases. This effect is important for photosynthesis because, according to Fermi’s golden rule, the rate of reaction is proportional to the density of photonic states. The calculation results are in good agreement with the experimental spectra.

We discuss algorithms and numerical challenges in constructing and resolving spectral problems for photonic crystal surface-emitting lasers (PCSELs) with photonic crystal layers and large (up to several tens of mm$^{2}$) emission areas. We show that finite difference schemes created using coarse numerical meshes provide sufficient accuracy for several major (lowest-threshold) modes of particular device designs. Our technique is applied to the example of large-area all-semiconductor PCSELs, showing how it can be used to optimize device performance.

Coherent perfect absorption (CPA) has been studied in various fields, such as metasurface, photonics, and acoustics, because of its ability to perfectly absorb light at a specific wavelength. However, the narrow bandwidth of CPA makes its application to on-chip photonics challenging. This limitation can be overcome by using a broadband resonator. Here, we demonstrate the coherent perfect loss (CPL) with respect to a single and broadband resonator at photonic crystal nanobeam. By using the finite element method, both cases of the CPL were simulated and optimized for the single and broadband resonators. In the optimized structure, a CPL occurs for both resonators. These results confirm that the perfect loss region for the broadband resonator is wider than that for the single resonator. These results are experimentally verified by fabricating both cases of CPL cases on a silicon-on-insulator by using electron beam lithography. An almost perfect loss of more than 95 % is observed for both single and broadband CPLs. Furthermore, the almost perfect loss region at the broadband resonator broadens more than that at the single resonator. The optimized structure for CPL has the potential for easy applications to on-chip photonics, such as optical switches, modulators, sensors, and logic gates.

In this work, we theoretically and experimentally study the induction of electromagnetic forces in an opal-based magnetic photonic glass, where light normally impinges onto a disordered arrangement of SiO2 spheres by the aggregation of Fe3O4 nanoparticles. The working wavelength is 633 nm. Experimental evidence is presented for the force that results from forced oscillations of the photonic structure. Finite-element method simulations and a theoretical model estimate the magnetic force volumetric density value, peak displacement, and velocity of oscillations. The magnetic force is of the order of 56 microN, which is approximately 500-times higher than forces induced in dielectric optomechanical photonic crystal cavities.

We have developed circular defects in 2-dimensional photonic crystal lasers that allow current injection for interconnected optical communications. However, when cleaving the sample to measure the output light, the output light intensity changes due to the cleaving position. In a previous study, we proposed a new end face structure called a convex edge structure. In this paper, we design the electron beam lithography patterns to fabricate this structure. With this design, it is possible to eliminate the effect of different cleaving positions and ensure that the cleavage tolerance is larger than the cleavage position error. We also develop the fabrication technology for this structure, fabricate samples, and measure the output light experimentally. The optical properties of the fabricated sample are similar to well-fabricated samples with normal cleavage edge faces. We are assured that these results contribute to future work such as accurate manufacturing and improving the end face configuration to obtain higher outputs.

In this paper, initially a photonic crystal is proposed with a periodic air gap and its performance is investigated at terahertz frequencies by varying the radius of the air gap. Then a microstrip array antenna on the 2-D photonic crystal using graphene sheet as patch material is designed and its electromagnetic characteristics are analysed and compared with those of the existing non-air gap antenna. The suggested antenna also operates in the multi-frequency terahertz range. Using a photonic band gap (PBG), crystal substrate causes the return loss to rise from −29 to −44 dB. Additionally, the antenna array's bandwidth was increased from 40 to 110 GHz. By using PBG, the gain of the suggested antenna is increased by up to 13 dB, as opposed to 4.81 dB for a substrate that does not use PBG. [ABSTRACT FROM AUTHOR]

Diabetes, characterized by chronic hyperglycemia, has become a major threat to human health. A noninvasive, continuous, and rapid visual detection of glucose is still a challenge in application. In this study, one-dimensional photonic crystals (1DPCs) prepared via layer-by-layer assembling of glucose-responsive poly-(acrylamide-N,N'-methylenebis-(acrylamide)-3-acrylamide phenylboronic acid) (P-(AM-MBA-AAPBA)) nanogels and TiO2 nanoparticles are first confirmed for rapid and continuous colorimetric detection of glucose in physiological conditions. A two-step swelling mechanism of PCs was designed to speed up glucose diffusion and recognition. In detection, the PC sensor with a thickness of about 200 nm can rapidly imbue the polymer layer with water, causing the polymer layer to swiftly swell and create a pathway for mass transfer. Then, glucose molecules permeate in PC's channels and bind to phenylboronic acid (PBA) sites, prompting secondary expansion. Due to the inherent hydrophilicity of the polymer and the nanoporous structure of the TiO2 layer, PC sensors exhibit exceptional responsiveness, reaching sensing equilibrium in glucose solution within 40 s and quickly reverting to their initial state within 1 s after adding diluted hydrochloric acid. The PC sensor effectively generates optical signals across a broad glucose concentration range of 0–100 mM and realizes continuous glucose detection. Notably, they can indicate the risk of diabetes with artificial urine, which provides a strategy for noninvasive glucose detection. In addition, the adsorption and desorption processes of glucose on PC are monitored with a quartz crystal microbalance with dissipation, and the reversible swelling of the nanogel layer is revealed, which provides valuable references for the mechanism study of PC glucose sensors. [ABSTRACT FROM AUTHOR]

By coating vinyl-modified silicon (Vi-SiO2) shell on the surface of polystyrene (PS) microspheres in alkaline medium, PS@SiO2 microspheres were synthesized using vinyltriethoxysilane (VTES) as silicon source. Subsequently, PS@SiO2 three-dimensional (3D) photonic crystals were prepared by rod-coating method and their optical properties were investigated. The synthesized PS microspheres and PS@SiO2 microspheres were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and infrared spectroscopy. Results showed that the stretching vibration absorption peaks of Si―O―Si at 1155 cm−1 and 1044 cm−1 in the infrared spectra proved the synthesis of Vi-SiO2. The PS@SiO2 microspheres had an obvious core-shell structure, with a Vi-SiO2 shell thickness of about 20 nm. At the same time, Vi-SiO2 formed a uniform and smooth shell on the surface of PS microspheres. Importantly, the coating of Vi-SiO2 had no significant effect on the monodispersity and sphericity of PS microspheres. The synthesized PS@SiO2 microspheres had particle sizes of 211, 230, 251 nm, and 270 nm, respectively. The cores of PS@SiO2 microspheres were PS microspheres with particle sizes of 177, 197, 218 nm, and 240 nm, respectively. Photonic crystals assembled from PS@SiO2 microspheres of four different particle sizes exhibited blue, green, yellow, and red structural colors, respectively, and the corresponding reflectance spectra showed reflection peaks at 475, 525, 575 nm, and 650 nm, respectively. Meanwhile, SEM images of photonic crystals assembled from PS@SiO2 microspheres of four different particle sizes all proved that PS@SiO2 photonic crystals had a regular face-centered cubic structure. In addition, PS@SiO2 photonic crystals displayed different structural colors at different viewing angles, meaning that they possessed iridescent effects. [ABSTRACT FROM AUTHOR]

Sulfamethoxazole (SMX) has numerous adverse effects and is present in various water systems; thus, the development of a rapid and accurate analytical method to detect SMX in water systems is crucial for protecting the environment and human health. A sulfamethoxazole molecularly imprinted photonic polymer (MIPP‐SMX) capable of facile naked‐eye recognition of target molecules was synthesized using the dual‐functional monomers acrylamide and methacrylic acid. The color of the MIPP‐SMX changed from green to blue in water samples containing sulfamethoxazole (SMX) in the concentration range of 0.5–5.0 mM. Furthermore, a linear correlation existed between the detected Bragg diffraction peak shift Δλ and SMX concentrations in water ranging from 0.5 to 2.0 mM. The detection limit for SMX was 0.3 mM. A recovery rate of 91.9%–108.5% was achieved when the polymer sensor was used to detect SMX in river water samples, with a relative standard deviation of 4.9%–6.0%. The designed MIPP‐SMX enabled rapid visual detection of SMX in water samples. The proposed method represents a significant advancement in the visual detection of SMX in environmental water samples. [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]

In this work, a biosensor based on two-dimensional photonic crystals is proposed. The structure is based on 30*20 silicon rods on the air background. The structure is considered for detection of Glucose and Creatinine concentrations in blood samples. This can help physicians in diagnosis of diabetes and kidney failure. The proposed biosensor is designed based on only linear materials to overcome low gain and nonlinearity difficulties. The functionality of the biosensor is fulfilled by considering the interference and scattering effects of Si defect rod situated in the structure (dark blue rods function as confining sensing media while dark green rods act as coupling rods). The proposed biosensor is designed in the format of hexagon shaped rings; filtering the operating resonance wavelengths. The functionality of the presented biosensor is investigated by considering the photonic band gap (PBG) and field distribution spectra, through the plane wave expansion (PWE) and finite-difference-time-domain (FDTD) methods. The incident light wave would be applied to the input port and according to the resonant wavelength would be transmitted to Outputs 1 or 2. The dimension of the proposed structure is considered as 114μm2 which makes it an appropriate option for optical integrated circuits. Finally, for Glucose, the remarkable sensitivity (1400 nm/RIU), quality factor (163.6—169.8), detection limit (6.6e-4—6.8e-4) RIU and figure of merit (150.4—152.6) RIU−1 were obtained. Similarly, for Creatinine, the sensitivity (795 nm/RIU), quality factor (53.5—58), detection limit (0.0029—0.0030) RIU and figure of merit (33.07—34.56) RIU−1 were achieved. [ABSTRACT FROM AUTHOR]

A biosensor based on 2-D photonic crystals is presented and considered. The proposed structure is made of 24 × 23 Si rods in the air background. The presented biosensor would be considered for detection of Cholesterol concentrations in blood samples, which can aid physicians in diagnosis of Hypercholesterolemia and heart diseases in early stages. To facilitate the designation and fabrication processes and overcome the gain and nonlinearity problems, only linear rods would be utilized. The presented structure operates based on the interference and scattering effects of Si defect rods positioned in the structure (black rods operate as the confining sensing media and dark green rods function as the coupling rods). The PANDA (the proposed structure indicates a PANDA face)-shaped waveguides can filter the resonant wavelengths. For studying the functionality of the proposed biosensor, photonic band gap (by the plane wave expansion (PWE) method) and field distribution (by the finite-difference-time-domain (FDTD) method) spectra should be considered. The appropriate dimension of the proposed biosensor (111.78 μm2) makes it a considerable option for utilization in bio-optical integrated circuits. Finally, for the Cholesterol concentrations in blood samples, the remarkable sensitivity (595.74 nm/RIU "RIU stands for refractive index unit"), quality factor (35–46), detection limit (6.1e−3–6.7e−3) RIU and figure of merit (14.89–16.3) RIU−1 were achieved. [ABSTRACT FROM AUTHOR]

A concept of a superradiant photonic crystal surface emitting laser (Super-PCSEL) is proposed. The proposal aims to tackle the problem of the catastrophical optical damage of facets of superradiant devices due to extreme power flux densities. The suggested design incorporates photonic crystal (PC) sections into femtosecond multiple contact superradiant structures. The potential configuration of the PC sections has been calculated by solving Maxwell equations using the finite differences time domain method. Proposed Super-PCSELs allow for increased reliability and the generation of much more powerful superradiant pulses as compared to presently available pulses. [ABSTRACT FROM AUTHOR]

In this paper an all-optical half adder has been designed on a 2D photonic crystal slab having air holes in a hexagonal lattice pattern. The working principal of the device is based on beam interference. Multi-mode interference based Pi phase shifter been used in this design. Neither any nonlinear materials nor any extra bias signal has been incorporated in the structure. Plain wave expansion and Finite Difference Time Domain methods have been used for analyzing the band diagram of the structure and performance of the proposed device respectively. The SUM port provides 60%, 67%, and 1% transmittance whereas the CARRY port provides 4%, 1%, and 90% transmission for {0,1}, {1,0}, and {1,1} logic combinations respectively. Minimum contrast ratio has been obtained as 18 dB in SUM port and 12.5 dB in CARRY port. Therefore, it is expected that the proposed all-optical adder would be a potential candidate for future generation photonic integrated circuits. [ABSTRACT FROM AUTHOR]

Micro-gyroscopes based on the Coriolis principle are widely employed in inertial navigation, motion control, and vibration analysis applications. Conventional micro-gyroscopes often exhibit limitations, including elevated noise levels and suboptimal performance metrics. Conversely, the advent of cavity optomechanical system technology heralds an innovative approach to micro-gyroscope development. This method enhances the device's capabilities, offering elevated sensitivity, augmented precision, and superior resolution. This paper presents our main contributions which include a novel dual-frame optomechanical gyroscope, a unique photonic crystal cavity design, and advanced numerical simulation and optimization methods. The proposed design utilizes an optical cavity formed between dual oscillating frames, whereby input rotation induces a measurable phase shift via optomechanical coupling. Actuation of the frames is achieved electrostatically via an interdigitated comb-drive design. Through theoretical modeling based on cavity optomechanics and finite element simulation, the operating principle and performance parameters are evaluated in detail. The results indicate an expected angular rate sensitivity of 22.8 mV/°/s and an angle random walk of 7.1 × 10−5 °/h1/2, representing superior precision to existing micro-electromechanical systems gyroscopes of comparable scale. Detailed analysis of the optomechanical transduction mechanism suggests this dual-frame approach could enable angular vibration detection with resolution exceeding state-of-the-art solutions. [ABSTRACT FROM AUTHOR]

The photonic crystal surface-emitting laser (PCSEL) has attracted much attention due to the advantages of a small far-field divergence angle and high output power. Here, we report a high-power terahertz (THz) photonic crystal laser with high beam quality through the optimization of the absorption boundary condition and the introduction of the symmetrically distributed electrodes. Single-mode surface emission at 3.4 THz with the maximum peak output power of 50 mW is demonstrated. Meanwhile, a high symmetric far-field pattern with C6 symmetry and a small divergence angle is achieved. In this device, the integration of the stable single-mode operation, high beam quality and high output power is realized, which may have great significance for practical applications. [ABSTRACT FROM AUTHOR]

In a wireless communication system, a microstrip patch antenna is gaining importance as a most powerful technology trend and it is applicable for the development of low-cost, minimal-weight, low-profile and high-performance antenna. This paper presents the design and the analysis of 1 × 2, 1 × 4 and 2 × 8 rectangular microstrip patch antenna (RMPA) arrays based on the photonic crystals for improved gain performance and high radiation characteristics compared to ones that are designed based on the homogeneous substrate in the frequency range of 0.25 - 0.55 THz. The design of the proposed antenna arrays based on the photonic band gap (PBG) and the homogeneous substrate structures is made by using the designed single-element RMPA as the basic building element, and then, they were fed by the parallel feeding structure. The designed antenna arrays were simulated using CST Microwave Studio software and validated with the aid of Ansoft HFSS simulator. For high radiation characteristics, the proposed antenna arrays resonated around 0.35 THz which is a low loss frequency window in the terahertz band. The main results showed that the designed antenna arrays based on the PBG substrate structure outperform the antenna arrays based on the homogeneous substrate in terms of return loss, bandwidth, gain and directivity. The best directivity was achieved by the 2 × 8 RMPA array of 17.40 dBi, whereas the 1 × 4, 1 × 2 RMPA arrays and single-element RMPA achieved the directivity of 13.54 dBi, 9.87dBi and 7.76 dBi, respectively. Hence, the designed antenna arrays can be used for medical imaging, threat detection and wireless surveillance communication. [ABSTRACT FROM AUTHOR]

Near-field lithography has evident advantages in fabricating super-resolution nano-patterns. However, the working distance (WD) is limited due to the exponential decay characteristic of the evanescent waves. Here, we proposed a novel photolithography method based on a modified photonic crystal (PC), where a defect layer is embedded into the all-dielectric multilayer structure. It is shown that this design can amend the photonic band gap and enhance the desired high- k waves dramatically, then the WD in air conditions could be extended greatly, which would drastically relax the engineering challenges for introducing the near-field lithography into real-world manufacturing applications. Typically, deep subwavelength patterns with a half-pitch of 32 nm (i.e., λ /6) could be formed in photoresist layer at an air WD of 100 nm. Moreover, it is revealed that diversified two-dimensional patterns could be produced with a single exposure using linear polarized light. The analyses indicate that this improved dielectric PC is applicable for near-field lithography to produce super-resolution periodic patterns with large WD, strong field intensity, and great uniformity. [ABSTRACT FROM AUTHOR]

We proposed and investigated an ultrahigh sensitivity terahertz (THz) refractive index sensor based on four‐inscribed hole defect photonic crystal structure. Due to the formation of resonant modes, the sensing properties can be obtained by shifting the sharp resonance in the transmission spectrum as changing of the analyte refractive index. In addition, the influence of structure parameters on the sensing performance is explored and demonstrated numerically. The numerical results illustrate that the Q‐factor and figure of merit reach 323.71 and 167.188 can be obtained under the optimized structural parameters. In particular, an ultrahigh sensitivity of 198.8 μm/RIU can be realized in the frequency range of 0.777–0.779 THz. The proposed sensor may find significant applications in biochemical sensing systems. [ABSTRACT FROM AUTHOR]

Presented in this paper is an experimental and numerical study of directiondependent asymmetry of resonant optical characteristics inherent to metal - multilayerdielectric (MMD) nanostructure, which has much in common with the Tamm plasmonic configuration. We demonstrate that when a MMD structure is illuminated from opposite sides, there is a noticeable asymmetry of the forward/backward reflection resonances, contrasting with the strictly symmetrical transmission resonances indicating classical optical reciprocity. Comparative measurements were carried out on a metal film and a quasi-periodic dielectric structure, which are identical to the corresponding parameters of the MMD structure. Directional asymmetry of reflection and transmission is briefly discussed for a modified MMD structure with the Kerr nonlinearity. [ABSTRACT FROM AUTHOR]

This article delves into the study of a novel metatronic amplifier through an electromagnetic analysis. The research involves both theoretical and numerical analysis to validate the findings. Due to the complex nature of the structure, an approximate electromagnetic analysis is conducted, which still provides valuable insights into its characteristics. The mode matching technique is employed to obtain amplifier characteristics that closely match the numerical results with a high degree of accuracy. This study sheds light on the potential applications of metatronic amplifiers in various fields and highlights their unique properties that make them stand out from traditional amplifiers. [ABSTRACT FROM AUTHOR]

In this study, a new four channel de-multiplexer with a ring resonator design is proposed. The bus waveguide and drop waveguide that make up the Ring Resonator are ring-shaped. In the proposed four channel demultiplexer design, one bus waveguide and four drop waveguides were built using a photonic crystal ring resonator. To improve output efficiency, the proposed demultiplexer was built with distinct inner radius values for each channel. With the resonance wavelengths for each channel in the range of 1552.4 nm, 1553.2 nm, 1554.1 nm, and 1555.4 nm, the suggested demultiplexer average quality factor was 7870.90, and its average transmission efficiency was 98.67%. The demultiplexer was created with a 0.8 nm narrow channel spacing with a − 15 dB to − 25 dB crosstalk range. The proposed ring resonator structure is made of silicon, which has a refractive index of 3.47, a center wavelength ranges of 1550 nm, and a lattice constant that varies with the radius range of 540 nm. To examine the performance, one can simulate the suggested demultiplexer structure using the FDTD (Finite-Difference Time-Domain) approach. The proposed work 198.7 µm2 footprint is appropriate for DWDM applications. [ABSTRACT FROM AUTHOR]

Shape memory photonic crystals (SMPCs) are smart composite materials with changeable structural color integrated by shape memory polymer and photonic crystals. SMPC can produce one or more temporary shapes through nanoscale deformation, memorizing current states. SMPC can be recovered to their original shapes or some intermediate states under external stimuli, accompanied by the variation of structural color. As porous carriers with built-in sensing properties, SMPCs promoted the interdisciplinary development of nanophotonic technology in materials science, environmental engineering, biomedicine, chemical engineering, and mechanics. Herein, the recent progress on multifunctional SMPCs and practical applications, including traditional and cold programmable SMPCs, is summarized and discussed. The primary concern is shape programming at the nanoscale that has demonstrated numerous attractive functions, including smart sensing, ink-free printing, solvent detection, reprogrammable gradient wetting, and controllable bubble transportation, under variations of the surface nanostructure. It aims to figure out the nanoscale shape memory effects on structural color conversion and additional performance, inspiring the fabrication of the next generation of SMPCs. Finally, perspectives on future research directions and applications are also presented. It is believed that multifunctional SMPCs are powerful nanophotonic tools for the interdisciplinary development of numerous disciplines in the future. [ABSTRACT FROM AUTHOR]

Twisted photonic crystals are photonic analogs of twisted monolayer materials such as graphene and their optical property studies are still in their infancy. This paper reports optical properties of twisted single-layer 2D+ moiré photonic crystals where there is a weak modulation in z direction, and bilayer moiré-overlapping-moiré photonic crystals. In weak-coupling bilayer moiré-overlapping-moiré photonic crystals, the light source is less localized with an increasing twist angle, similar to the results reported by the Harvard research group in References 37 and 38 on twisted bilayer photonic crystals, although there is a gradient pattern in the former case. In a strong-coupling case, however, the light source is tightly localized in AA-stacked region in bilayer PhCs with a large twist angle. For single-layer 2D+ moiré photonic crystals, the light source in Ex polarization can be localized and forms resonance modes when the single-layer 2D+ moiré photonic crystal is integrated on a glass substrate. This study leads to a potential application of 2D+ moiré photonic crystal in future on-chip optoelectronic integration. [ABSTRACT FROM AUTHOR]

Porous silicon 1D photonic crystals, namely rugate filters, are covered with a loosely packed hexagonally ordered array of stimuli‐responsive hydrogel microgels, and the optical properties of the resulting hybrid sensor are thoroughly investigated. For this purpose, both rugate filters with and without hydrogel microgel on top are immersed in ethanol/water mixtures possessing different compositions and NaCl solutions. Reflectance spectra of all samples are taken and analyzed concerning the spectral positions and reflectance intensity of the strong peak related to the photonic crystal rugate peak as well as the side bands resulting from Fabry–Pérot interference at the interfaces bordering the porous silicon. For the latter analysis, a Fourier transform is applied to the side bands for calculating the effective optical thickness (EOT). Thereby it can be shown that the spectral position of both the rugate peak and the EOT peak is best suited for monitoring refractive index changes in the immersion medium whereas the swelling and collapse of the stimuli‐responsive hydrogel microgel can be only detected by variations in the amplitude of the rugate peak and the EOT peak. These results are confirmed by simulations using a simple geometrical model and shall serve as guide for developing tailor‐made optical sensors. [ABSTRACT FROM AUTHOR]

In this article, an electrostatically-actuated NEMS XOR gate is proposed based on photonic crystals for hardware implementation of binary neural networks. The device includes a 2D photonic crystal which is set on a movable electrode to implement the XOR logic using the transmission of specific wavelengths to the output. This design represents the importance of the proposed structure in which the logic gate operation is not dependent on the contact of its conductive layers. Consequently, one of the major issues in MEMS-based logic gates, which is due to the contact of the operating electrodes and may cause stiction problem, reducing the reliability of the system, can be tackled by the present approach. Furthermore, according to the simulation results, the functional characteristics of the present NEMS XOR gate are obtained as follows: pull-in voltage of Vp = 8V, operating voltage of Vo = 10V and switching time of ts = 4 μs. The results also show that the proposed design provides a classification error rate of between 1% to 12%, while used in neural network implementation. This error can be negligible compared to the state-of-the-art designs in neural network implementation. These appropriate parameters of the present NEMS gate make it a promising choice for the implementation of neural networks with a high network accuracy even in the presence of significant process variations. [ABSTRACT FROM AUTHOR]

Options for using ordered 3D arrays of photonic crystals for the generation of gigahertz, optical, and neutron radiation upon interaction with a beam of high-energy electrons are considered. The optical emission spectra of photonic crystals produced in the interaction with a beam of relativistic electrons are presented. Experiments were carried out to obtain 2D images of objects in gamma and neutron fluxes generated in the interaction of an electron beam with a photonic crystal material. Various neutron generating targets are considered, for which the corresponding neutron yields were calculated. The characteristics of electromagnetic and neutron fields obtained in the experiment are also presented. [ABSTRACT FROM AUTHOR]

Unlike absorption‐based colors of dyes and pigments, reflection‐based colors of photonic crystals, so called "structural colors", are responsive to external stimuli, but can remain unfaded for over ten million years, and therefore regarded as a next‐generation coloring mechanism. However, it is a challenge to rationally design the spectra of structural colors, where one structure gives only one reflection peak defined by Bragg's law, unlike those of absorption‐based colors. Here, we report a reconfigurable photonic crystal that exhibits single‐peak and double‐peak structural colors. This photonic crystal is composed of a colloidal nanosheet in water, which spontaneously adopts a layered structure with single periodicity (407 nm). After a temperature‐gradient treatment, the photonic crystal segregates into two regions with shrunken (385 nm) and expanded (448 nm) periodicities, and thus exhibits double reflection peaks that are blue‐ and red‐shifted from the original one, respectively. Notably, the transition between the single‐peak and double‐peak states is reversible. [ABSTRACT FROM AUTHOR]

Tensile strained GeSn alloys are considered a key enabler for the realization of complementary metal‐oxide‐semiconductor laser sources. However, the tensile strained GeSn lasers reported to date require complex fabrication processes for applying tensile strain in GeSn, preventing tensile GeSn lasers from becoming the mainstream technology for integrated photonics. Here, a unique strain engineering method is presented that can introduce a uniform tensile strain in GeSn lasers by harnessing a widely developed atomic layer deposition (ALD) process. 1D photonic crystal nanobeam lasers under homogenous tensile strain induced by an ALD HfO2 all‐around stressor layer show a single‐mode lasing peak with a ≈31 nm redshift and ≈2 times intensity increase. The lasing threshold of tensile strained GeSn lasers is ≈12% improved compared to the unstrained GeSn lasers. It is believed that the approach offers a new path toward the realization of practical group‐IV laser sources for photonic‐integrated circuits. [ABSTRACT FROM AUTHOR]

Topological nature in different areas of physics and electronics has often been characterized and controlled through topological invariants depending on the global properties of the material. The validity of bulk–edge correspondence and symmetry-related topological invariants has been extended to non-Hermitian systems. Correspondingly, the value of geometric phases, such as the Pancharatnam–Berry or Zak phases, under the adiabatic quantum deformation process in the presence of non-Hermitian conditions, are now of significant interest. Here, we explicitly calculate the Zak phases of one-dimensional topological nanobeams that sustain guided-mode resonances, which lead to energy leakage to a continuum state. The retrieved Zak phases show as zero for trivial and as π for nontrivial photonic crystals, respectively, which ensures bulk–edge correspondence is still valid for certain non-Hermitian conditions. [ABSTRACT FROM AUTHOR]

This work focused on developing nanoscale plasmonic gratings and photonic crystals using unique quantum structures, specifically Graphene nanoribbons and PbSe quantum dots, within a metal-dielectric-metal (MIM) multilayer waveguide structure. These structures are designed to operate at a wavelength of 1550 nm and exploit the interaction between electromagnetic waves and free electrons to excite surface plasmon polaritons (SPPs) to create unique optical susceptibility for the nanostructures considering the possibility of control of the chemical potential of the Graphene nanoribbon. The primary goal of this research is to create nanoscale optical devices based on photonic crystals with improved capabilities by incorporating plasmonic structures, such as Graphene nanoribbons and PbSe quantum dots, to manipulate light at the nanoscale. These are sheets of graphene with specific dimensions (775 × 40 nm2) that are bonded to a SiO2 platform. An array of PbSe quantum dots with a radius of 10 nm is placed on the nanoribbons. This waveguide structure is used to confine and guide electromagnetic waves. The system operates at a wavelength of 1550 nm, which is within the optical telecommunication band. The nanostructure interacts with incident electromagnetic waves, exciting surface plasmon polaritons (SPPs) within the MIM waveguide. This excitation induces polarization in the PbSe quantum dots, leading to changes in the amplitude of the incident wave. The induced dipoles in the quantum dots result in a unique optical susceptibility for the nanostructure. This susceptibility depends on the geometry and optical constants of the materials used in the structure. The research aims to provide a foundation for using these nanostructures in photonic crystal-based optical devices in the future. These devices may have applications in various fields, such as telecommunications, sensors, and integrated photonics. Overall, this work focused on harnessing plasmonic and quantum properties to develop advanced nanoscale optical components, and the results could have implications for the development of next-generation photonic devices. [ABSTRACT FROM AUTHOR]

This paper focuses on designing a simple photonic crystal fiber (PCF) biosensor. The proposed glucose sensor is modelled by Lumerical software using the finite element method. To evaluate the efficiency of this model, different sensing properties such as birefringence, coupling length, and relative sensitivity are calculated at different air-filling fractions. The principle of this PCF is to detect the variations in the refractive index of the different concentration glucose solutions. The analyte will be injected into an elliptical channel surrounded by two rings of air holes in a hexagonal shape. Numerical simulations show that increasing the air-filling fraction yields high performance and more light confinement. At the air-filling fraction of 0.45, the maximum birefringence and relative sensitivity were 4.01 × 10−3 and 91%, respectively. Also, the coupling length reaches a minimum of 162.09 μm. [ABSTRACT FROM AUTHOR]

Increasing the speed of operation in all optical signal processing is very important. For reaching this goal one needs high speed optical devices. Optical half adders are one of the important building blocks required in optical processing. In this paper an optical half adder was proposed by combining nonlinear photonic crystal ring resonators with optical waveguides. Finite difference time domain method wase used for simulating the final structure. The simulation results confirmed that the rise time for the proposed structure is about 1 ps. [ABSTRACT FROM AUTHOR]