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Circularly polarized luminescence is essential to chiral and photonic science, but achieving circularly polarized thermally activated delayed fluorescence (CP‐TADF) and circularly polarized room‐temperature phosphorescence (CP‐RTP) simultaneously remains a great challenge. This is because it is difficult to satisfy simultaneously the stable triplet exciton, appropriate energy gap, and the regular chiral environment. Herein, a simple strategy is reported to construct a persistent photoluminescent system, which can achieve TADF and RTP simultaneously by suppressing the non‐radiative transition decay of the triplet exciton through intermolecular hydrogen bonding between acridine flavin (AF) and rigid polymer network. The persistent photoluminescent composite exhibited ultra‐long lifetimes and high quantum yields. Then, a rarely multi‐circularly polarized photoluminescence system containing CP‐TADF and CP‐RTP is constructed by the co‐assembly of cellulose nanocrystals, polyvinyl alcohol, and AF. By utilizing the cholesteric structure, photonic band gap of chiral photonic crystals, and the stabilization mechanism of triplet exciton by intermolecular hydrogen bonding between the light emitter and rigid polymer, chiral photoluminescent films exhibited rare optical properties simultaneously: multi‐circularly polarized photoluminescence emission, high and tunable dissymmetric factor, significant quantum yield, and ultralong lifetimes, which are not reported before and broaden the perspective for multi‐circularly polarized luminescence. [ABSTRACT FROM AUTHOR]

This paper uses the Transfer Matrix Method (TMM) to investigate the transmission rate and the photonic band structure of one-dimensional photonic comb-like waveguides (CWGs) system. This study is crucial as it provides valuable insights into the properties of photonic waveguides, which can be leveraged to design high-performance guiding, filtering and multiplexing devices. The primary objective of our study is to comprehend the impact of defects on the transmission and band structure of CWGs. Specifically, how changes the geometrical and material properties of defective resonators affect defect modes in photonic band gaps. By modifying the relative permittivity and length of these defective resonators, we observed a shift of defect modes to lower frequencies. This work shows, for the first time, the influence of these defects on defect modes and their potential applications in the development of high-performance guidance and electromagnetic filtering devices. [ABSTRACT FROM AUTHOR]

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

A nanoscale-based 2D-photonic crystal (PhC) biosensor with silicon rods arranged in a triangular lattice structure is proposed in this work. The unique characteristic of the proposed structure is the design of dual nanocavity where two different rod radii are used within the ring resonator. The plane-wave expansion (PWE) method is used to analyse photonic band gaps (PBGs) and the sensing parameters are analysed using finite difference time domain (FDTD) techniques. The proposed biosensor is aimed at detecting the brain tissues, human immune deficiency virus (HIV)–infected blood samples, and sickle cell anaemia. The sensor proved its efficiency in detecting and distinguishing accurately between the brain tissues that are normal and aberrant (tumorourous, malignant, and damaged tissues). The proposed sensor achieves a high-quality factor (QF) of 9867, a high sensitivity of 1105 nm/RIU with an extremely low detection limit (DL) of 0.70 × 10−5, towards brain tissue analysis. This sensor can distinguish between a normal blood sample and HIV-infected samples. The QF, sensitivity, and DL of the biosensor for the HIV-infected sample are 2720, 1034 nm/RIU, and 2.61 × 10−5 RIU respectively. The sensor also proved its efficiency in analysing sickle cell anaemia in the blood sample. The QF and sensitivity of the biosensor are 6428 and 1071 nm/RIU respectively towards anaemia prediction. The proposed nanoscale photonic sensor could be a promising platform for other biomedical applications, such as the detection of various diseases at the cellular level. [ABSTRACT FROM AUTHOR]

In this article, a theoretical study of Tamm plasmon based Refractive Index (RI) sensor for cancer cell detection has been proposed. The proposed sensor structure comprises of a thin titanium nitride (TiN) layer of thickness (dm = 30 nm) followed by a liquid cell of thickness (dL = 1500 nm) then followed by 16 pairs of semi-porous DBR (spDBR). The high and low index layers of spDBR constitute of silicon nitride (Si3N4) and porous Si3N4, respectively. We considered the porosity of low-index layer as 75%. The existence of Tamm plasmon between TiN and spDBR interface and the effect of porosity on the photonic band gap (PBG) of the spDBR have been studied as well. The impact of dm and dL on the reflection spectrum of the proposed structure has also been investigated. We investigated the detection of cancer-affected cells by replacing the liquid cell with respective cancer-affected cell and its corresponding normal cell, including blood cancer (Jurkat), cervical cancer (HeLa), adrenal gland cancer (PC12), two types of breast cancer (MDA-MB-231 and MCF-7), and skin cancer (Basal) cells. The proposed structure achieved the sensitivity, Q-factor, figure of merit, and detection limit of 752.85 nm/RIU, 131.64, 70.62 RIU−1, and 5 × 10−4 RIU, respectively. The proposed design can also be utilized in biological and gas sensing applications. [ABSTRACT FROM AUTHOR]

Radiation detection is being revolutionized by integrating photonic elements into scintillators. In this study, a scalable and cost‐effective method is proposed to achieve tuneable emission enhancement across the visible spectrum by colloidal self‐assembly of photonic crystals on scintillator surfaces. This concept is demonstrated for Eu3+/Tb3+‐doped Gd and Ta oxides. Widely available and affordable colloidal nanospheres of SiO2 or polymethyl methacrylate are self‐assembled on these scintillators. The size of the nanospheres is carefully optimized to match the desired emission lines of Eu3+/Tb3+. The result is homogeneous and closely‐packed structures with clear photonic bandgap in the visible range. Under X‐ray excitation, the scintillators covered with the photonic layers exhibit enhanced light extraction in the direction perpendicular to the surface, compared to isotropic emission in the bare scintillator. Such scintillation directionality, when optically matched with a proper detector, will result in higher efficiency of the overall detection system. Moreover, X‐ray imaging demonstrates an enhancement of 25% in system resolution of the scintillator supplemented with the photonic layer compared to unmodified scintillators. The proposed method is scintillator‐ and nanosphere‐agnostic, thus offering a promising versatile approach for directing the scintillation light toward a photodetector and increasing detection system performance, including high‐resolution imaging applications. [ABSTRACT FROM AUTHOR]

The optical properties of strongly doped semiconductor nanocrystals depend strongly on the carrier density of the nanocrystals. These characteristics can be exploited for the design of innovative optical devices based on ultrafast switching potentially in the THz modulation bandwidth. In this study, the optical response of one‐dimensional photonic crystals incorporating colloidal nanoparticles of a highly doped semiconductor such as indium tin oxide (ITO) is investigated, taking into consideration the angular dependence of the photonic band gap and the position dependence of the photonic band gap on the light‐induced tunability of the ITO doping. [ABSTRACT FROM AUTHOR]

Photonic Band Gap (PBG) crystals have shown their significant role in optical data processing. Again it is seen that in optical communication and computation, Frequency Shift Keying (FSK) can extend a potential application. In PBG also the FSK can show its usefulness. The main novelty of the proposed work is the implementation of an optical FSK system designed on a 2D PBG crystal. The proposed structure contains a square-shaped lattice formed by GaAsInP-doped rods placed in an air-based substrate along with photonic crystal-based Semiconductor Optical Amplifiers (pc-SOAs). The authors also presented a theoretical model that successfully demonstrates the operation of the FSK system in the optical domain with simulation experiment. This work uses a moderate input light power and operates at a very high-speed (Tbps). Here, a ring cavity resonator with a constant biasing signal is incorporated to realize the FSK model. The intensity-encoded Boolean signal and the photonic crystal-based two Semiconductor Optical Amplifiers (pc-SOAs) are used here to establish the FSK scheme where the Boolean 1 (presence of optical signal) is encoded by another light having a frequency υ1 and the Boolean 0 (absence of light) is encoded by another frequency of light υ2. As the FSK is developed in the optical domain using the switching character of PBG, hence a moderate light power is enough to conduct this implementation. In this communication, the optical FSK is designed and analyzed by a simulation process with Finite-Difference-Time-Domain (FDTD) and Plane Wave Expansion (PWE) techniques. [ABSTRACT FROM AUTHOR]

Polymer-stabilized cholesteric liquid crystals (PSCLCs) have emerged as promising candidates for one-dimensional photonic lattices that enable precise tuning of the photonic band gap (PBG). This work systematically investigates the effect of polymer concentrations on the AC electric field-induced tuning of the PBG in PSCLCs, in so doing it explores a range of concentrations and provides new insights into how polymer concentration affects both the stabilization of cholesteric textures and the electro-optic response. We demonstrate that low polymer concentrations (≈3 wt. %) cause a blue shift in the short wavelength band edge, while high concentrations (≈10 wt. %) lead to a contraction and deterioration of the reflection band. Polarization optical microscopy was conducted to confirm the phase transition induced by the application of an electric field. The observations confirm that increased polymer concentration stabilizes the cholesteric texture. Particularly, the highly desired fingerprint texture was stabilized in a sample with 10 wt. % of the polymer, whereas it was unstable for lower polymer concentrations. Additionally, higher polymer concentrations also improved the dissymmetry factor and stability of the lasing emission, with the dissymmetry factor reaching the value of around 2 for samples with 10 wt. % of polymer additive. Our results provide valuable comprehension into the design of advanced PSCLC structures with tunable optical properties, enhancing device performance and paving the way for innovative photonic applications. [ABSTRACT FROM AUTHOR]

This paper proposes a model of Waveguide Photonic Band Gap (WPBG) structures, based on the Leaky Mode Propagation (LMP) method, to perform a complete analysis of electromagnetic (e.m.) wave propagation, including radiation loss, for a structure of finite extension. The LMP method allows for the detailed examination of the interaction between guided modes and radiative modes, providing insight into how energy leaks from the waveguide. This model enables the accurate prediction of both the confinement and loss characteristics of the WPBG structures, making it suitable for applications where both controlled wave propagation and minimized energy dissipation are crucial. Furthermore, we demonstrate the effectiveness of this approach through simulations and discuss its potential impact on the design of photonic devices. [ABSTRACT FROM AUTHOR]

During the last decades, 2D-ordered and disordered photonic systems have attracted intense attention as systems capable to control and modify the flow of light. These structures can also localize light into a bandgap by exciting states arising from cavities, defects, or photonic molecules. We report a controllable random disordered photonic system of silicon dielectric cylinders that presents a deep bandgap and, superimposed, two tunable resonant states generated from decagonal ring resonators embedded into it. These states show a high transmission intensity and a bandwidth that remains stable when its geometrical parameters for frequency tuning are modified. The ability to tune resonating frequencies with geometrical parameters of the system allows interesting applications such as sensing and filtering. [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]

Circularly polarized light emitting active materials are of great interest, and the convenient tuning of the circularly polarized luminescence (CPL) remains a significant challenge. Integrating fluorescent materials into chiral photonic crystals to achieve tunable CPL is a promising approach, allowing efficient manipulation of CPL by adjusting the photonic band gap (PBG). We combined carbon quantum dots (CQDs) with hydroxypropyl cellulose (HPC), which self-assembles into a cholesteric liquid crystal (CLC). The helical structure can selectively reflect right circularly polarized (RCP) light, achieving strong circular dichroism (CD) and high CPL dissymmetry factor glum. In addition, the chiral template is thermo-responsive. The CPL wavelength can be adjusted by regulating the PBG position through temperature adjustment, while the chirality of CPL keeps high especially in the heating process. This work enables stimuli-responsive manipulation of CPL under one template through temperature regulation, which may open up enormous possibilities for the cellulose-based material in different areas. [ABSTRACT FROM AUTHOR]

This work presents an innovative platform of a multi-channel one-dimensional photonic crystal (1-DPC) based on blood refractive index data of different patients in the aspect of the main protein components like hemoglobin. This photonic crystal (PC) contains a defect center infiltrated with plasma using a microorder size syringe. When binary silica and III–V semiconductor (InSb) materials are combined, they increase the refractive index difference between the alternate layers of the composite material, resulting in a wide photonic band gap (PBG). We use the well-known transfer matrix method (TMM) to observe the reflectance of various blood samples that were previously published. We assess and contrast the influence of different refractive index data on the dynamic shift in PBG calculation for novel superior and resourceful sensor in the prevention of microscopic organisms such as SARS-CoV-2, the virus linked with COVID-19. Yet, the performance of this PC has more moral content and unlimited casting efficacy in the face of an incurable virus. [ABSTRACT FROM AUTHOR]

In this article, we have theoretically demonstrated the sensor performance in mid-IR frequency domain by resonance excitation of Bloch surface modes through energy coupling with graphene surface plasmon polaritons in truncated one-dimensional (1D) ternary photonic crystal (TPC) under Kretschmann configuration coupling technique. The involvement of optical anisotropy via graphene monolayer enhances light-matter interaction thus enabling excellent control over the resonance wavelength (RW) of the excited Bloch surface modes (EBSMs). For incident transverse magnetic-polarized electromagnetic waves, the band structure, reflection spectra and field profile are computed using 2 $ \times $ × 2 transfer matrix method. The control over the RW has been established by examining the effect of variation of different model parameters like thickness of truncation layer, refractive index of external medium, temperature, chemical potential and the periodicity of TPC. The variations in periodicity result in the expansion of the range of confinement of EBSMs in photonic band gaps from $ 19 \textrm{THz} $ 19 THz to $ 65 \textrm{THz} $ 65 THz . We proved that the variation in temperature between $ 300^\circ\textrm{K} $ 300 ∘ K and $ 500^\circ\textrm{K} $ 500 ∘ K confines the EBSMs with high coupling efficiency (CE). Also, at room temperature the best achievable quality factor (QF) is 1421 and a high Q.F. of 8170 is attained at $ 260^\circ\textrm{K} $ 260 ∘ K . [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]

This paper presents the design and analysis of a temperature sensor that utilizes an optical filter consisting of an elliptical-shaped photonic crystal ring resonator (E-PhCRR) in a two-dimensional configuration. The basic structure comprises silicon (Si) rods immersed in the air (disconnected structure) arranged in a triangular lattice. The newly designed structure's photonic band gap (PBG) was calculated using the plane wave expansion (PWE) method, and the temperature sensor was modeled and studied using the finite difference time domain (FDTD). The temperature change causes a redshift in the resonance wavelength due to the subsequent change in refractive index. The temperature was systematically adjusted within the range of 0 °C to 50 °C, leading to a discernible change in the resonant wavelength by 5.2 nm, shifting it from 1682.59 nm to 1687.79 nm. The elliptical shape of the photonic crystal ring resonator provided us with significant flexibility to attain improved outcomes. Specifically, we achieved a quality factor of 316200, a temperature sensitivity of 103.92 pm/°C, and a refractive index sensitivity of 443 nm/RIU. Furthermore, we were able to acquire a detection limit of 5.12 × 10 - 9 RIU while maintaining a compact size of 116.5 μ m 2 . [ABSTRACT FROM AUTHOR]

Conjugated polymers have attracted significant attention in the field of photocatalysis due to their exceptional properties, including versatile optimization, cost-effectiveness, and structure stability. Herein, two conjugated porous polymers, PhIN-CPP and ThIN-CPP, based on triazines, were meticulously designed and successfully synthesized using benzene and thiophene as building blocks. Based on UV diffuse reflection spectra, the photonic band gaps of PhIN-CPP and ThIN-CPP were calculated as 2.05 eV and 1.79 eV. The PhIN-CPP exhibited a high hydrogen evolution rate (HER) of 5359.92 μmol·g−1·h−1, which is 10 times higher than that of Thin-CPP (538.49 μmol·g−1·h−1). The remarkable disparity in the photocatalytic performance can be primarily ascribed to alterations in the band structure of the polymers, which includes its more stable benzene units, fluffier structure, larger specific surface area, most pronounced absorption occurring in the visible region and highly extended conjugation with a high density of electrons. The ΔEST values for PhIN-CPP and ThIN-CPP were calculated as 0.79 eV and 0.80 eV, respectively, based on DFT and TD-DFT calculations, which revealed that the incorporation of triazine units in the as-prepared CMPs could enhance the charge transfer via S1 ↔ T1 and was beneficial to the photocatalytic decomposition of H2O. This study presents a novel concept for developing a hybrid system for preparation of H2 by photocatalysis with effectiveness, sustainability, and economy. [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]

Extensive radiative transfer calculations to fit the more significant average spectral features displayed in measured reflectance spectra by cuticles of Chrysina resplendes scarabs have been carried out. A simulated annealing approach is the starting point to optimize the values of the spatial average uric acid volume fraction, the thickness of the retarder layer located between the two left-handed chiral structures in the cuticle, and the slope of the parameter describing the variation with depth of the uric acid volume fraction through the retarder layer. Both twisted arrangements are characterized in terms of their photonic behaviors to display the variation with depth of the photonic band gaps, effective refractive index and birefringence, wave numbers and relative densities of states. [ABSTRACT FROM AUTHOR]

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

A novel terahertz polarization isolator using a two-dimensional square lattice tellurium rod array is numerically investigated at the interesting band of 0.22 THz in this short paper. The isolator is designed by inserting six hexagonal tellurium rods into a fully polarized photonic crystals waveguide with high efficiency of −0.34 dB. The TE and TM photonic band gaps of the 7 × 16 tellurium photonic crystals are computed based on the plane wave expansion method, which happen to coincide at the normalized frequency domain from 0.3859(a/λ) to 0.4033(a/λ), corresponding to the frequency domain from 0.2152 to 0.2249 THz. The operating bandwidth of the tellurium photonic crystals waveguide covers 0.2146 to 0.2247 THz, calculated by the finite element method. The six hexagonal tellurium rods with smaller circumradii of 0.16a serve to isolate transverse electric waves and turn a blind eye to transverse magnetic waves. The polarization isolation function and external characteristic curves of the envisaged structure are numerically simulated, which achieves the highest isolation of −33.49 dB at the central frequency of 0.2104 THz and the maximum reflection efficiency of 98.95 percent at the frequency of 0.2141 THz. The designed isolator with a unique function and high performance provides a promising approach for implementing fully polarized THz devices for future 6G communication systems. [ABSTRACT FROM AUTHOR]

Topological photonic crystal provides a platform for robust energy transport in photonic systems. In this letter, we propose a method for realizing rainbow trapping and releasing based on the topologically protected defect modes in dielectric photonic crystals. The photonic states of different frequencies are separated and trapped at different positions to form the topological rainbow. The all-dielectric planar nanostructures consist of deformed honeycomb lattices and a gradient 1D array, which is distinct from previous platforms where edge states appear at the interface between trivial and nontrivial crystals. Due to the simplification of the configuration, we can selectively control the stop position of the wave by modifying the bottom row of dielectric rods so that light can switch between the trapping state and releasing state. The robustness of the slowing light system is also investigated. These results are beneficial to multiple frequency tuning. The simplified structure could offer a novel method for micro-miniaturizing and applying optical communication equipment, such as optical storage and optical buffer. [ABSTRACT FROM AUTHOR]

We explore theoretically Goos-Hänchen (GH) shift around the defect mode in superconducting defective photonic crystals (PCs) in cryogenic environment. The defective PCs are constructed by alternating semiconductors and superconductors. A defect mode arises in the photonic bandgap and sensitively depends on environment temperature and hydrostatic pressure. Reflection and transmission coefficient phases make an abruptly jump at the defect mode and giant GH shifts have been achieved around this mode. The maximum GH shift can get as high as 103λ (incident wavelength), which could be modulated by the values of temperature and hydrostatic pressure. This study may be utilized for pressure- or temperature-sensors in cryogenic environment. [ABSTRACT FROM AUTHOR]

We explore theoretically Goos-Hänchen (GH) shift around the defect mode in superconducting defective photonic crystals (PCs) in cryogenic environment. The defective PCs are constructed by alternating semiconductors and superconductors. A defect mode arises in the photonic bandgap and sensitively depends on environment temperature and hydrostatic pressure. Reflection and transmission coefficient phases make an abruptly jump at the defect mode and giant GH shifts have been achieved around this mode. The maximum GH shift can get as high as 103λ (incident wavelength), which could be modulated by the values of temperature and hydrostatic pressure. This study may be utilized for pressure- or temperature-sensors in cryogenic environment. [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]

A high-gain and tri-band terahertz microstrip antenna with a photonic band gap (PBG) substrate is presented in this paper for terahertz communications. Polyimide dielectric columns are inserted into the silicon substrate to form the PBG substrate to improve the gain of the antenna. The PBG substrate and polyimide substrate constituted a multilayer substrate structure and enabled the multi-band operation of the antenna. The PBG substrate antenna achieves gains of 6.28 dB, 4.84 dB, and 7.66 dB at resonant frequencies of 0.360 THz, 0.580 THz, and 0.692 THz, respectively, outperforming the homogeneous substrate THz microstrip antenna (H antenna) by 1.18 dB, 1.74 dB, and 1.82 dB, respectively. The radiation efficiencies at three operating bands are over 93%, 92%, and 88%, respectively, which are slightly higher than that of the H antenna and greater than that of the standard multi-band antenna. [ABSTRACT FROM AUTHOR]

With the rising demand for the transmission of large amounts of information over long distances, the development of integrated light circuits is the key to improving this technology, and silicon photonics have been developed with low absorption in the near-infrared range and with sophisticated fabrication techniques. To build devices that work in different functionalities, photonic crystals are one of the most used structures due to their ability to manipulate light. The investigation of photonic crystals requires the calculation of photonic band structures and is usually time-consuming work. To reduce the time spent on calculations, a trained ANN is introduced in this study to directly predict the band structures using only a minimal amount of pre-calculated band structure data. A well-used 1-D fishbone-like photonic crystal in the form of a nanobeam is used as the training target, and the influence of adjusting the geometric parameters is discussed, especially the lattice constant and the thickness of the nanobeam. To train the ANN with very few band structures, each of the mode points in the band structure is considered as a single datapoint to increase the amount of training data. The datasets are composed of various raw band structure data. The optimized ANN is introduced at the end of this manuscript. [ABSTRACT FROM AUTHOR]

The possibility of complete absorption of an incident electromagnetic wave in a narrow frequency band by a two-dimensional array of metal nanoparticles placed in the surface layer of a one-dimensional photonic crystal structure is demonstrated. The nature of the influence of the parameters of an array of nanoparticles (particle shape, interparticle distance) on the reflection and absorption spectra of the photonic structure in the photonic band gap is determined. [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]

Photonic crystals are artificial structures with a spatial periodicity of dielectric permittivity on the wavelength scale. This feature results in a spectral region over which no light can propagate within such a material, known as the photonic band gap (PBG). It leads to a unique interaction between light and matter. A photonic crystal can redirect, concentrate, or even trap incident light. Different materials (dielectrics, semiconductors, metals, polymers, etc.) and 1D, 2D, and 3D architectures (layers, inverse opal, woodpile, etc.) of photonic crystals enable great flexibility in designing the optical response of the material. This opens an extensive range of applications, including photovoltaics. Photonic crystals can be used as anti-reflective and light-trapping surfaces, back reflectors, spectrum splitters, absorption enhancers, radiation coolers, or electron transport layers. This paper presents an overview of the developments and trends in designing photonic structures for different photovoltaic applications. [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 paper, a new structure of 2D photonic crystals for all-optical 4-bit adder based on kerr effect and ring resonators is proposed. The fundamental rods are made of silicon material with a refractive index is about 3.476 around a wavelength 1550 nm. The lattice constant of the PhC structure, and the radii of fundamental dielectric rods are about 592 nm, and 118 nm, respectively. The structure is designed using in a cascade one half adder and three full adders. The optical adder is composed of nonlinear ring resonators, input ports (Ai, Bi), and output ports (Si, Ci). The ring resonators R1 and R2 based on the optical kerr effect are created by replacing 2 × 24 dielectric rods are made of nonlinear material doped glass with a linear and nonlinear refractive index of 1.4 and 10−14 m2/W, respectively. The radii of these dielectric rods are 90 nm and 80 nm. The input and output ports are located in the best position, and the total footprint is about 2229 μm2. We used COMSOL Multiphysics Software based on the plane wave expansion and the finite element methods to simulate the photonic band gap diagram and the light propagation inside the PhC structure. The proposed 4-bit adder can be used in the next generation of optical computer systems applications and photonic integrated circuit communication. [ABSTRACT FROM AUTHOR]

In this study, a one-dimensional defective photonic structure for the detection of magnetic fluid in the presence of an external magnetic field has been theoretically examined by using TMM. The principle of capillary action has been used for injecting the magnetic fluid under consideration into the cavity region of the proposed photonic structure. The sensing capability of the structure has been examined by analyzing the presence of defect mode inside the photonic bandgap of the structure under normal incidence condition only for neglecting the problems involved during oblique incidence. We have optimized the thickness of the cavity layer as 670 nm in order to achieve high value of sensitivity 312.50 nm/RIU from the proposed design under the influence of an external magnetic field of value 210 Oe. Apart from sensitivity, we have also examined figure-of-merit and quality factor values of the suggested design to establish support toward our claim of designing of sensitive magnetic sensor composed of one-dimensional defective photonic structure. The work can be used for designing of some novel photonic structures for sensing and detection of magnetic field strength via magnetic fluid. [ABSTRACT FROM AUTHOR]

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]

We investigate the transmittance spectrum of a multichannel filter composed of dielectric (A) and plasma (P) materials in the microwave region within the transfer matrix formalism. Two configurations of the proposed filter are studied under the influence of an applied magnetic field: (1) a periodic structure containing (A / P) N unit cells surrounded by air and (2) the introduction of a second dielectric material (D) acting as a defect layer to produce an (A P) N / 2 / D / (A P) N / 2 structure. Our findings reveal that in the periodic case, the number of resonant states of the transmittance increases with number N ; however, the observed blue and red shifts depend on the intensity and orientation of the applied magnetic field. We present contour plots of the transmission coefficients that show the effect of the incident angle on the shifts of the photonic band gaps. Furthermore, we find that the introduction of a defect layer generates additional resonant states and merges the central resonant peak into a miniband of resonances. Moreover, we show that the number of resonant peaks and their locations can be modulated by increasing the unit cell number, N , as well as increasing the width of the inserted defect layer. Our proposed structures enable the design of novel photonic filters using magnetized plasma materials operating in the microwave region. [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 PCF-SPR sensor was theoretically proposed with high sensitivity and a wide RI range. The sensor design employs a photonic bandgap structure with a hexagonal pore distribution. The PCF sensor demonstrated high sensitivity for both x-polarized and y-polarized light, achieving maximum sensitivities of 14,250 nm/RIU and 14,000 nm/RIU, respectively. Furthermore, the sensor is capable of detecting RI variations within the range of 1.19–1.53. Specific pore configurations were studied for their effects on sensing performance, revealing that both RI detection region and maximum wavelength sensitivity (WS) decrease as the pores between the gold and analyte move outward. As the core analyte diameter increases, the RI detection range of the PCF sensor decreases. However, the maximum WS increases with an increase in the core diameter. Increasing the pitch causes an increase in RI, while the maximum WS increases and then decreases. The study also shows that a regular hexagonal air hole distribution will only result in quadrupole resonance, whereas a quasi-regular hexagonal air hole distribution will show dipolar resonance. Dipolar resonance can extend the working wavelength to the mid-infrared range and improve both the RI range and sensitivity. The influence of air holes on the RI detection range can be explained by the equivalent medium method, and the influence on the sensitivity can be explained by the optical transmission theory. [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]

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

We demonstrate optical nonthermal excitation of exchange dominated spin waves of different orders in a magnetophotonic crystal. The magnetophotonic structure consists of a thin magnetic film and a Bragg stack of nonmagnetic layers to provide a proper nonuniform interference pattern of the inverse Faraday effect induced by light in the magnetic layer. We found a phenomenon of the pronounced phase slippage of the inverse Faraday effect distribution when the pump wavelength is within the photonic band gap of the structure. It allows to tune the interference pattern by a slight variation of light wavelength which results in the modification of excitation efficiency of the different order spin waves. The approach can be applied for different magnetic dielectrics expanding their application horizons for spin-wave based devices. [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]

In this paper, a novel microstrip resonator technique for temperature sensing is proposed, designed, and implemented using a hybrid planar microstrip line and photonic band gap (PBG) structure. To implement the PBG structure of the microstrip line, a microfluidic channel with periodic form is introduced into the substrate and filled with water. The operation principle of the sensor is based on a frequency shift due to the variation in the center of the band gap, which in turn changes with the variation of the permittivity of water, which relates to the temperature. The different empirical expressions describing the complex permittivity with the resonant frequency were carried out. The proposed sensor is simple in design and low cost, which may be applied in different applications at the industrial. [ABSTRACT FROM AUTHOR]

A new approach to determining the sensitivity of refractive index sensors is proposed. It has been shown that relative and absolute sensitivity show different results, and also, for the first time, it is demonstrated that relative sensitivity has advantages over absolute sensitivity. In addition, the influence of the relative width of the photonic band gap and the difference in the refractive indices of the layers on the sensitivity are examined and the corresponding dependences of these parameters are obtained. We propose these parameters as a convenient tool for optimizing the sensitivity of sensors based on defective photonic crystals. Finally, results are obtained regarding the behavior of the defect mode at the center of the photonic band gap of one-dimensional photonic crystals. [ABSTRACT FROM AUTHOR]