Photonic Crystal Structure Research Articles

Iterative approach for photonic crystal devices design

Background. An approach to the design of photonic crystal (PhC) devices is proposed, which differs from the known general-purpose optimization methods (for example, a genetic algorithm or gradient procedures) by using information about diffraction patterns at different frequencies when optimizing an element designed to operate at the selected wavelength. The following is an approach to the design of photonic crystal elements. The proposed approach differs from known general-purpose optimization methods (e.g., genetic algorithm or gradient procedures) by using diffraction pattern information at different frequencies while optimizing an element designed to operate at the selected wavelength. The design of functional PhC structures with expected characteristics (for example, waveguides) for a certain wavelength (albeit given by a monochromatic radiation source) is described. Aim. Development based on the FDTD method and confirmation of the functionality of the iterative procedure for calculating the characteristics of metal-dielectric PhC lattices. Methods. The study is based on an iterative approach to the design of PhC elements based on the use of the FDTD method. Results. Model examples were used for demonstration of practical convergence and applicability of the developed iterative procedure. The efficiency of the PhC waveguide, understood as the ratio of the output energy to the input energy, was increasing at each iteration up to 97.2%. Conclusion. The method of synthesis of metal-dielectric PhC structures with preset properties based on application of developed iterative procedure is proposed and argued. The results of the analysis of the 2D PhC waveguide based on a set of round copper rods show the applicability of the proposed method.

Gan Photonic Crystals: Spectral Dynamics in UV, X‐Ray, and Alpha Radiation

In this work, a comparative analysis of gallium nitride (GaN) thin films is conducted, both with and without photonic crystal (PhC) structures, focusing on their scintillation and photoluminescence properties. GaN's suitability for diverse optoelectronic and radiation detection applications is analyzed, and this study examines how PhC implementation can enhance these properties. Methodologically, the emission spectra is analyzed from 5.9 keV X‐ray sources, decay curves, pulse height spectra in response to 241Am 5.5 MeV alpha‐rays, and photoluminescence spectra induced by UV excitation. The findings demonstrate a substantial increase in quantum efficiency for PhC GaN, nearly tripling the light yield that of conventional plain GaN thin films under the UV excitation. The enhancement is predominantly attributed to the PhC GaN's proficiency in guiding light at 550 nm, a feature indicative of its spectral filtering capabilities, as detailed in the study. Furthermore, side‐band scintillations, stemming from inherent materials like Chromium that generate scintillations at diverse wavelengths, are effectively mitigated. A key finding of this study is the effective detection of light not only at the rear but also along the lateral sides of the films, offering new possibilities for radiation detector design and architecture.

Exploiting the Bragg Mirror Effect of TiO2 Nanotube Photonic Crystals for Promoting Photoelectrochemical Water Splitting

Exploiting the Bragg mirror effect of photonic crystal photoelectrode is desperately desired for photoelectrochemical water splitting. Herein, a novel TiO2 nanotube photonic crystal bi-layer structure consisting of a top nanotube layer and a bottom nanotube photonic crystal layer is presented. In this architecture, the photonic bandgap of bottom TiO2 nanotube photonic crystals can be precisely adjusted by modulating the anodization parameters. When the photonic bandgap of bottom TiO2 nanotube photonic crystals overlaps with the electronic bandgap of TiO2, the bottom TiO2 nanotube photonic crystal layer will act as a Bragg mirror, leading to the boosted ultraviolet light absorption of the top TiO2 nanotube layer. Benefiting from the promoted UV light absorption, the TiO2 NT-115-NTPC yields a photocurrent density of 1.4 mA/cm2 at 0.22 V vs. Ag/AgCl with a Faradic efficiency of 100%, nearly two times higher than that of conventional TiO2 nanotube arrays. Furthermore, incident photon-to-current conversion efficiency is also promoted within ultraviolet light region. This research offers an effective strategy for improving the performance of photoelectrochemical water splitting through intensifying the light–matter interaction.

All optical half adder and subtractor using single 2D photonic crystal structure

All optical half adder and subtractor using single 2D photonic crystal structure

Pearl‐Inspired Colored Carbon Fibers with Electromagnetic Interference and Optical Camouflage Properties

Carbon fibers (CFs) are widely used in cutting‐edge and civilian fields due to their excellent comprehensive properties such as high strength and high modulus, superior corrosion and friction resistances, excellent thermal stability, light weight, and high electrical conductivity. However, their natural ultra‐black appearance is difficult to meet the aesthetic needs of today's civilian sector and the need for optical stealth in the military field. In addition, conventional coloring methods are difficult to effectively adhere to CF surfaces due to high crystallinity and highly inert surface caused by their graphite‐like structure. In this work, inspired by the nacre structural color of pearls, colored CFs with 1D photonic crystal structure are prepared by cyclically depositing amorphous (Al2O3 + TiO2) layers on the surface of carbon CFs through atomic layer deposition (ALD). The obtained CFs exhibit brilliant colors and excellent environmental durability in extreme environments. Moreover, the colored CFs also exhibit high EMI shielding effectiveness (45 dB) and optical stealth properties, which can be used in emerging optical devices and electromagnetic and optical stealth equipment.

Absorption of electromagnetic waves by cylindrical surface plasmon resonance

Abstract The absorption characteristics of cylindrical surface plasmon resonance (CSPR) have been studied. We demonstrated that a single plasma column with CSPRs can achieve high absorptivity at the plasmon frequency. We also studied the effects of plasma density and collision frequency on the absorptivity. As both of them increase, the corresponding absorptivity tends to increase first and then decrease, but with different reasons. Such manifestation is explained by analyzing transmission and reflection spectra in both cases, as well as magnetic field distribution patterns at the frequency of plasmon. On the one hand, the increase in plasma density leads to the enhancement of plasmons, improving transmittance; On the other hand, the increase in collision frequency leads to a weakening of plasmons and an increase in reflectivity. Finally, we investigated the absorption characteristics of plasmons in the plasma photonic crystals (PPCs) structure and overcame the absorption attenuation caused by the increase in plasma density by increasing the number of plasma columns. Meanwhile, the absorption generated by surface plasmon resonance is not affected by the lattice constant of PPCs. The research has shown that efficient absorption can be achieved using CSPR, resulting in extremely high absorptivity when using fewer plasma columns. Finally, we verified the absorption ability of CSPRs through experiments.

All-optical simultaneous OR and AND optical logic gates based on nonlinear photonic crystal ring resonator

Abstract An all-optical simultaneous OR and AND logic gates using the nonlinear Kerr effect and ring resonator based on a two-dimensional photonic crystal are proposed in this paper. The proposed structure has a resonant wavelength of 1551.3 nm and a power consumption (1 kW/μm2). The proposed structure is suitable for all-optical photonic integrations because of its simplicity and small size (23 μm x 30.4 μm). Moreover, the structure executes two logic operations without requiring an additional spare/control signal through a single structure, making fabrication easy. The total footprint of the photonic crystal ring resonator structure measures approximately 699 μm². A very high contrast ratio of 26.10 dB and 25.34 dB is obtained for the OR and AND logic gates, with response times equal to 2 ps and 0.67 ps, respectively. In addition, the calculated bit rates for OR and AND logic gates are approximately 0.5 and 1.5 Tbps, respectively. Using the Rsoft CAD commercial software, the FullWAVE and BandSOLVE module of the software is used for numerical and theoretical investigation of the structure.

Smart photonic crystal hydrogels for visual glucose monitoring in diabetic wound healing

Diabetes is a global chronic disease that seriously endangers human health and characterized by abnormally high blood glucose levels in the body. Diabetic wounds are common complications which associate with impaired healing process. Biomarkers monitoring of diabetic wounds is of great importance in the diabetes management. However, actual monitoring of biomarkers still largely relies on the complex process and additional sophisticated analytical instruments. In this work, we prepared hydrogels composed of different modules, which were designed to monitor different physiological indicators in diabetic wounds, including glucose levels, pH, and temperature. Glucose monitoring was achieved based on the combination of photonic crystal (PC) structure and glucose-responsive hydrogels. The obtained photonic crystal hydrogels (PCHs) allowed visual monitoring of glucose levels in physiological ranges by readout of intuitive structural color changes of PCHs during glucose-induced swelling and shrinkage. Interestingly, the glucose response of double network PCHs was completed in 15 min, which was twice as fast as single network PCHs, due to the higher volume fraction of glucose-responsive motifs. Moreover, pH sensing was achieved by incorporation of acid-base indicator dyes into hydrogels; and temperature monitoring was obtained by integration of thermochromic powders in hydrogels. These hydrogel modules effectively monitored the physiological levels and dynamic changes of three physiological biomarkers, both in vitro and in vivo during diabetic wound healing process. The multifunctional hydrogels with visual monitoring of biomarkers have great potential in wound-related monitoring and treatment.Graphical abstract

Design and fabrication of photonic crystal structures by single pulse laser interference lithography

Photonic crystal (PhC) structures formed by periodic surface nanostructuring have emerged as pivotal elements for controlling light-matter interactions. One important application is reducing losses due to the high surface reflectivity of semiconductor optoelectronic devices, such as enhancing light absorption in photovoltaic cells or improving light extraction in light-emitting diodes (LEDs). Although various methods for fabricating such structures have been documented, the utilization of single pulse laser interference lithography (LIL) using commercial photoresist and its subsequent effective use as an etch mask has not been previously reported. Rapid exposure of photoresists with single nanosecond pulses offers benefits for high throughput patterning and reduces the requirement for a stable optical platform. We have successfully employed single pulse LIL to fabricate antireflective PhC structures on GaAs substrates using a commercial photoresist. Exposure is performed with single 7 ns 355 nm pulses of relatively low energy (<10 mJ). High-quality nanohole arrays of pitch of approximately 365 nm are fabricated and depths up to 400 nm have been etched using inductively coupled plasma (ICP) through the exposed photoresist mask. Reflectivity analyses confirmed that these structures reduce the average reflectance of the GaAs to below 5 % across the 450 nm to 700 nm visible wavelength range. The fabrication of PhC structures using this approach has potential for low-cost wafer-level patterning to provide improved light extraction in LEDs and enhanced light trapping in solar cells.

Refractive index sensing characteristics of PCF-SPR based on dual-plasmon materials

Abstract In this paper, a photonic crystal fiber (PCF) refractive index sensor based on surface plasmon resonance (SPR) with dual plasmonic materials (indium tin oxide and gold) is proposed. We innovatively designed a dual-core PCF structure and pore arrangement effectively enhancing the coupling effect. Using two different plasma materials, phase matching is achieved at two different wavelengths for the evanescent and surface plasmon waves, resulting in dual resonance peaks. The refractive index sensing is accomplished by measuring the dual-peak resonance shift, which expands the detection wavelength and RI detection ranges. The sensor can detect analytes with refractive indices ranging from 1.32 to 1.43 at wavelengths between 0.4 um and 1.4 um. We optimized the photonic crystal fiber structure and studied the sensing performance of the sensor, improving its sensitivity. Simulation results indicate that the designed PCF sensor exhibits outstanding maximum dual-peak shift sensitivity (DPSS), reaching up to 28,000 RIU-1, along with maximum amplitude sensitivity (AS) and wavelength sensitivity (WS) of 18,500 RIU-1 and 34,500 RIU-1, respectively, in the direction of y-polarization. Furthermore, the sensor achieves high resolution, and the figure of merit (FOM) values can reach up to 5.134×10-7 and 2758. Consequently, the proposed sensor can provide high-precision and extensive-range measurements of solution refractive indices within the visible and infrared light spectrum, and it holds potential application prospects in numerous fields, such as food safety testing and chemical substance detection.&amp;#xD;

Tunable Fano-type resonance with quadrature squeezing in a double-cavity-waveguide structure of photonic crystals

We propose an optical approach to realizing Fano-type spectra of quadrature squeezing in a double-cavity-waveguide structure based on photonic crystals (PhCs). In this scheme, a partially transmitting element (PTE) in the waveguide creates the transmission and reflection light, which interferes with the outflow from the intracavity field and subsequently gives rise to Fano-type interference. Meanwhile, a degenerate parametric amplifier (DPA) embedded into the cavity is expected to yield quantum squeezed states in the interference process. After verifying the existence of the Fano resonance, we report that increasing the nonlinear gain of the DPA not only amplifies the transmitted intensity of the output field, but also improves its quadrature squeezing degree. More importantly, we illustrate that, when maintaining the high performance of quadrature squeezing, the linewidths and frequencies of the asymmetrical spectra can be modulated by adjusting the double-cavity coupling strength. This combination of Fano-type spectra and quadrature squeezing is beneficial for optimizing optical communications and signal processing with a low noise level.

Highly sensitive one-dimensional Dielectric-Superconductor photonic crystal structure for low temperature sensing applications

The work proposed in this paper investigates the design and simulation of low temperature refractive-index (RI) sensor using one-dimensional photonic crystal (1D-PhC) structure. The bilayer stack is created using dielectric and superconductor materials. The dielectric material is assumed to be air and the superconductor considered is YaBa2Cu3O7. Compared to superconductor material, air’s RI is hardly affected by the temperature. The parameter perceived by the suggested sensor for precise temperature measurement in the region of 10 K to 90 K is thought to be the superconductor’s RI, which is a function of temperature. To the best of our knowledge, the structural characteristics have been precisely adjusted to increase sensor efficiency to a level never before seen in published research. According to the findings, the temperature sensitivity of 1.524 nm/K and the maximum RI sensitivity of 1079.42 nm/RIU are found in the proposed structure. Applications for bio-sensing are a good fit for the suggested sensing device.

ZIF-8-CdS photonic crystal beads for slow photon effect induced enhanced photocatalysts

The unique periodic structure of photonic crystals demonstrates an effective slow photon effect that enhances the interaction between light and matter. This study designed and prepared MOF photonic crystal beads, and significantly improved the photocatalytic efficiency by utilizing the slow light effect. Utilizing microfluidic technology, ZIF-8 was self-assembled to form photonic crystal beads (PCB-Z) to enhance adsorption properties and light absorption. The surface of PCB-Z is modified with CdS to form a heterostructure (PCB-ZC), which widens the absorption spectrum, reduces the carrier recombination rate, and increases the specific surface area, while the photocurrent intensity of PCB-ZC is about 1.8 and 29 times that of CdS and PCB-Z. Under the combined effect of photonic crystal structure, ZIF-8/CdS heterojunction and slow photon effect, the degradation rate of Rhodamine B by PCB-ZC was 15.22 times higher than the disordered ZIF-8 powder, and the photocatalytic performance was significantly improved. The dominant role of holes in Rhodamine B degradation was confirmed by free radical trapping experiments and EPR tests. This research confirms that MOF-based photonic crystals can be assembled into periodic structures to enhance adsorption properties and light absorption, which provides a new paradigm for the development of MOF-based photocatalysts.

Observation of multifunctional robust topological states based on asymmetric C4 photonic crystals

Recent advancements in high-order topological insulators have heralded new opportunities for the innovation and utilization of optical devices. This paper presents a composite asymmetric C4 photonic crystal to achieve multifunctional, robust topological states. Through detailed analysis of the fine changes in the topological bandgap induced by distortion parameters, we facilitate the realization of topological edge states in wavelength division multiplexing applications. We utilize both trivial and nontrivial properties of the topological bandgap to precisely manipulate zero-dimensional angular states, one-dimensional topological boundary states, and two-dimensional body states. Through simulations and experimental results, our advanced asymmetric C4 photonic crystal structure demonstrates superior robustness for the transmission of topological edge states. Our research paves the way for the deployment of more robust topological boundary state transmission systems and advances the application potential of higher-order topological states.

Selective IR wavelengths multichannel filter based on the one-dimensional topological photonic crystals comprising hyperbolic metamaterial

In this research article, we have theoretically introduced a one-dimensional topological photonic crystal (1D TPC) design to provide a better stability due to imperfections and fluctuations in geometry compared to the traditional PC structures. The considered structure is designed by the combination of two different PCs, i.e., PC1 and PC2. PC1 consists of two layers of silicon (Si) and magnesium fluoride (MgF2), while PC2 contains a multilayer stack of MgF2 and hyperbolic metamaterial (HMM). Interestingly, the HMM layer is introduced as a composite of a dielectric material of indium arsenide (InAs), and nanocomposite of Ag nanoparticles inside a hosting medium of Y2O3. The foundations of our theoretical framework are based on Effective Medium Theory (EMT), the Transfer Matrix Method (TMM), and the Maxwell-Garnett model. Our research primarily focuses on utilizing our design as a pass/stop band filter for near-infrared (NIR) applications. Notably, this proposed design exhibits significant stability in the face of imperfections and variations. Our numerical findings highlight the influence of several geometric parameters including the refractive index of hosting medium for Ag nanoparticles, thicknesses, and filling fraction on the characteristics of the resulting filter. Remarkably, the results also reveal the emergence of multiple resonance peaks that maintain high stability against geometric tolerances. We believe our work presents a finite photonic crystal (PC) whose wave localization properties are resilient to random geometric imperfections, making it suitable for NIR filtering applications.

Selective enhancement of deep ultraviolet luminescence in barium fluoride scintillators via photonic crystal structures

Selective enhancement of deep ultraviolet luminescence in barium fluoride scintillators via photonic crystal structures

Synthesis of Doped g‐C3N4 Photonic Crystals for Enhanced Light‐Driven Hydrogen Production from Catalytic Water‐Splitting

Dopants are frequently used to improve graphitic carbon nitride (gCN) photoactivity. As a doping source, phosphomolybdic acid (PMA) can activate doping sites inside the gCN lattice, resulting in 2D Mo:P‐gCN porous material. However, the gradual loading of the PMA fraction has no systematic improvement in the Mo:P‐gCN photoactivity. For improving the optoelectronic properties of Mo:P‐gCN, its textural geometry is a controllable parameter that can provide enhanced photonic properties, achievable by shaping its morphology through a crystalline template structure, namely, photonic crystals (PCs). Herein, a doped PC material is made of Mo:P‐gCN and PCs and labeled as Mo:P‐gCN/PCs. The impact of PCs is highlighted in the structural, electronic, and optical performances of Mo:P‐gCN. A well‐defined 3D crystalline network is evidenced by microscopic measurements (scanning electron microscopy, AFM, focused ion beam). Mo:P‐gCN/PCs shows a hydrogen production rate (750 μmol g−1 h−1) one time higher than Mo:P‐gCN and 6 times higher than pure gCN. The synthesis strategy proposed in this work leads simultaneously to the Mo:P codoping effect provided by PMA and the slow photon effect due to the PC structure, offering a novel strategy to improve the gCN photoactivity by simultaneously applying polyoxometalates as modifiers and polystyrene opals as templates.

Enhanced Photocatalytic Properties and Photoinduced Crystallization of TiO2-Fe2O3 Inverse Opals Fabricated by Atomic Layer Deposition.

The use of solar energy for photocatalysis holds great potential for sustainable pollution reduction. Titanium dioxide (TiO2) is a benchmark material, effective under ultraviolet light but limited in visible light utilization, restricting its application in solar-driven photocatalysis. Previous studies have shown that semiconductor heterojunctions and nanostructuring can broaden the TiO2's photocatalytic spectral range. Semiconductor heterojunctions are interfaces formed between two different semiconductor materials that can be engineered. Especially, type II heterojunctions facilitate charge separation, and they can be obtained by combining TiO2 with, for example, iron(III) oxide (Fe2O3). Nanostructuring in the form of 3D inverse opals (IOs) demonstrated increased TiO2 light absorption efficiency of the material, by tailoring light-matter interactions through their photonic crystal structure and specifically their photonic stopband, which can give rise to a slow photon effect. Such effect is hypothesized to enhance the generation of free charges. This work focuses on the above-described effects simultaneously, through the synthesis of TiO2-Fe2O3 IOs via multilayer atomic layer deposition (ALD) and the characterization of their photocatalytic activities. Our results reveal that the complete functionalization of TiO2 IOs with Fe2O3 increases the photocatalytic activity through the slow photon effect and semiconductor heterojunction formation. We systematically explore the influence of Fe2O3 thickness on photocatalytic performance, and a maximum photocatalytic rate constant of 1.38 ± 0.09 h-1 is observed for a 252 nm template TiO2-Fe2O3 bilayer IO consisting of 16 nm TiO2 and 2 nm Fe2O3. Further tailoring the performance by overcoating with additional TiO2 layers enhances photoinduced crystallization and tunes photocatalytic properties. These findings highlight the potential of TiO2-Fe2O3 IOs for efficient water pollutant removal and the importance of precise nanostructuring and heterojunction engineering in advancing photocatalytic technologies.

Fabrication of Photonic Crystal Structures on GaAs by Single Pulse Laser Interference Lithography

Fabrication of Photonic Crystal Structures on GaAs by Single Pulse Laser Interference Lithography

Optical properties of the 1D quasiperiodic photonic crystals comprising gyroidal superconductor for THz applications

The present research proposes a quasiperiodic 1D photonic crystal structure, which is designed with a successive arrangement of gyroidal geometry-based Bismuth Strontium Calcium Copper Oxide (BSCCO) superconducting material and SiO2 following a 10th order of Fibonacci sequences. The numerical simulation is carried out using the transfer matrix method to study the transmittance characteristics over a broad band of THz frequency range. The effects of various structural parameters such as filling fraction of BSCCO in the gyroidal layer, hosting materials of the gyroidal layer, and the Fibonacci sequence order on the transmission spectrum are extensively analyzed. It is observed that by suitably dealing with these parameters, we can easily control the number of stop bands, and the cutoff frequency as well. Therefore, the designed structure can be considered as an apt candidate for multichannel filtering applications in the THz frequency regime.