Photonic Crystal Structure Research Articles

Mechanochromic and Conductive Gels Based on Cellulose Nanocrystals for Bioinspired Sensing.

Soft mechanochromatic materials hold great promise for wearable sensing technologies. Bioinspired photonic crystal structures assembled from cellulose nanocrystals (CNCs) enable dynamic light modulation, providing a vibrant and easily controlled optical platform for real-time detection. This study constructed a CNC-based mechanochromic and conductive gel with a dual-signal response featuring interactive optical and electrical feedback. The mechanical response is achieved through the integration of encapsulating, interpenetration, and crystallization of a soft biocompatible poly(vinyl alcohol) (PVA) sandwich matrix, which propels the deformation of the encased CNC photonic crystal core, leading to dynamic changes in conductivity and color. The material exhibits the capability of detecting dynamic tensile/compressive strains (up to 130%/49% along with a visually discernible color shifting from red to blue) and recognizing finger bending and specific spoken words, which showcases its potential in pliable dual-signal sensing in human health monitoring and strain detection.

Photonic crystal fibre optic sensor based on a U-shaped detection channel with large air-hole cladding

A photonic crystal fibre-optic sensor based on a U-shaped detection channel with a large aperture cladding has been designed for refractive index sensing and detection, taking advantage of the flexibility of the photonic crystal fibre-optic structure and its superior performance. The results show that the relative intensities and central wavelengths of the directional coupling absorption peaks of the photonic crystal fibre-optic sensor are closely related to the ratio of the long and short semi-axes of the U-shaped detection channel and the thickness of the gold nanofilm. The sensor has a sensitivity of up to 21700 nm/RIU in the refractive index range of 1.33–1.43, a resolution of 4.608 × 10−6 RIU and a maximum quality factor of 126.12 RIU−1. Photonic crystal fibre-optic sensors with large-aperture cladding and U-shaped detection channels are simple in structure, highly sensitive and have significant potential applications in environmental monitoring, medical assays and industrial control.

Performance analysis of the photonic crystal–based X-OR gate for the terahertz applications

Abstract A key component of high-speed switching networks is an optical logic gate. This study presents the design and analysis of an all-optical XOR gate based on a two-dimensional photonic crystal (2D PC) structure, aiming to enhance high-speed switching in optical networks. The XOR gate, with two input and one output waveguide, is constructed on a hexagonal lattice, optimized for operation at a wavelength of 1,550 nm. The design is evaluated using the Finite Difference Time Domain (FDTD) approach, which simulates the optical performance of the structure. Key performance metrics, including the bit rate, contrast ratio, and delay time, are computed, showing that the proposed logic gate achieves a high contrast ratio of 30.35 dB and a minimal delay time of 0.4 ps. The results confirm the potential of this all-optical XOR gate for integration into high-speed optical circuits, offering low power consumption and high efficiency. This work demonstrates the feasibility of utilizing photonic crystal structures for high-performance optical logic gates in future communication systems. The simplicity of fabrication in a two-dimensional photonic crystal (2D-PC)-based all-optical logic gate can often be attributed to its simple design.

Coupling Bifunctional Scaffolds with Slow Photon Effect for Synergistically Enhanced Photoassisted Lithium-Sulfur Battery Properties.

Photoassisted lithium-sulfur (Li-S) batteries offer a promising approach to enhance the catalytic transformation kinetics of polysulfide. However, the development is greatly hindered by inadequate photo absorption and severe photoexcited carriers recombination. Herein, a photonic crystal sulfide heterojunction structure is designed as a bifunctional electrode scaffold for photoassisted Li-S batteries. Inverse opal (IO) structures utilize a slow photon effect that originates from their adjustable photonic band gaps, giving them distinctive optical response characteristics. The incorporation of a SnS/ZnS heterojunction within these IO frameworks further broadens the light absorption spectrum and enhances the charge transfer process. This efficient IO hybrid bifunctional electrode not only enhances the adsorption and conversion of polysulfides at the cathode but also induces uniform Li nucleation at the anode. These contribute the full batteries to output a high reversible capability of 1072 mAh g-1 and maintain stable cycling for 50 cycles. Additionally, a specific capacity of 698.8 mAh g-1 is still obtained even under a sulfur loading of up to 4 mg cm-2. The present strategy on SnS/ZnS IO to enhance photoassisted Li-S battery properties can be extended to rationally construct other energy storage devices.

Fabrication strategies and microscale sensing functionalities of mechanochromic colloidal photonic crystals for underwater applications

Mechanochromic colloidal photonic crystals (PCs), which typically integrate a self-assembled PC array with a highly elastic medium, exhibit the ability to reversibly respond to external mechanical stimuli by altering the periodicity of PC structures. Nowadays, leveraging visible indications and optical signals for mechanical forces, mechanochromic colloidal PCs have been widely used in reflecting body motion, health monitoring, and communications in daily life. However, despite their extensive applications on land, it is vital to explore the potential of mechanochromic sensing applications underwater, where message transmission mainly relies on body gestures and motions. This review comprehensively examines recent advancements in mechanochromic colloidal PCs and their underwater applications. The first part introduces the response mechanism of mechanochromic colloidal PCs, emphasizing the main principles that facilitate sensing on the microscale. The second part describes the fabrication strategies for constructing these PCs, demonstrating various approaches to establish optical sensors with specific functionalities. The final section discusses the confronted challenges and summarizes the potential opportunities in developing mechanochromic colloidal PCs for underwater sensing applications.

Design and analysis of optical devices with ultra-high quality factor based on a plasmonic photonic hybrid structure

Abstract In the present paper, the design of a tunable, high transmitting, and optical ultra-narrow band-pass filter using a plasmonic-photonic hybrid structure comprised of a multilayer stack of dielectrics and a thin sheet of silver is proposed. This current design can create more energy coupling, thus having a higher transmission peak in comparison to prior studies. To obtain a filtering operation, two different topologies are designed to achieve better performance specifications. The materials used in the structure include silicon, silicon-dioxide, and silver. The Drude model is employed for the silver. It has been shown that the geometrical parameters are sensitive to choose such that transmission properties and resonance wavelengths are arbitrarily tunable. The structure's design enables a single-mode as well as a multi-mode spectrum for each topology. We have achieved a maximum quality factor of 432.87 with an ultra-small full-width-at-half-maximum bandwidth of 1.43 nm, while the maximum transmission values are greater than 75%. Most of the various advantages include adjustability, high detection resolution, and integration at the nanoscale for optical applications owing to the basic merits of the hybrid structures of plasmonic and photonic crystals.

Optical Transmission Enhancement of MoS2 Nanosheets Doped with Magnetic Materials Ni, Mn, and Cr

In this work, we report both theoretical and experimental study of the influence of some materials with magnetic aspects such as Ni, Mn, or Cr in MoS2 photonic crystal structures. A functional density method technique has been introduced. Indeed, the results indicated that the transmission spectrum is considerably affected by the impact of doping from a photo shape and amplitude. Furthermore, appropriate doping has been shown to change the peak transmission shape of the MoS2 photonic crystal by splitting as an example. In fact, the transmission spectrum remains less identical with Ni and Mn doping and exhibits a doubling peak with Cr attributed to the first and second waveguide propagation modes. The obtained results can give a new degree of freedom in device application of MoS2 nanosheets such as photonic sensors, filter, and reflector. Finally, we can predict that the MoS2 photonic crystal doped with magnetic materials could be used in applications involving plasmonic Fano-resonances. Received: 29 July 2024 | Revised: 4 November 2024 | Accepted: 27 December 2024 Conflicts of Interest The authors declare that they have no conflicts of interest to this work. Data Availability Statement Data sharing is not applicable to this article as no new data were created or analyzed in this study. Author Contribution Statement Sondes Kaddour: Conceptualization, Formal analysis, Writing – original draft. Randa Zaimia: Formal analysis, Investigation. Nouha Mastour: Validation, Investigation. Said Ridene: Methodology, Writing – review & editing, Supervision. Noureddine Raouafi: Resources.

Analysis of Low-Threshold 1D Perovskite Photonic Crystal Laser

By using the bandgap effect and light localization effect, photonic crystal lasers can decrease the optical mode volume and lower the laser threshold, so satisfying the requirements for device shrinking and photonic integration. Given their wide range of potential applications in fields including light-emitting diodes and sensors, they are attracting considerable interest. The laser threshold is the minimum energy density required to cause laser oscillation and is a crucial specification for the practical application of laser devices. Perovskite materials, equipped with their exceptional optical gain characteristics, are well-suited for the development of low-threshold lasers. By combining them with photonic crystal lasers, it is possible to realize low-threshold or even threshold-free pumped lasers. This paper categorizes photonic crystal lasers according to their photonic crystal structures and examines the advancements in research on perovskite photonic crystal lasers in attaining low minimum thresholds. This work investigates the prospective capabilities of perovskite photonic crystal lasers, with the objective of achieving laser output that is low-threshold or near-zero-threshold, high-power, and of high quality.

Improving the performance of quantum well solar cells with photonic crystal.

The fabrication of quantum well solar cells with surface photonic crystal (SPC) and embedded photonic crystal (EPC) structures has resulted in solar cells with improved properties. When compared to reference solar cells (RSCs), the photoluminescence (PL) intensities of SPC solar cells and EPC solar cells have been enhanced by 89% and 114%, respectively. This indicates improved light absorption and emission characteristics in the presence of the periodic patterns (PCs). The short-circuit current (Isc) of EPC solar cells is 31% higher than that of RSCs, suggesting improved light absorption and carrier generation. On the other hand, SPC solar cells exhibit a 6% higher Isc compared to RSCs, and the open-circuit voltage has increased simultaneously. The fill factors (FF) of the solar cells are 84% for RSCs, 86% for SPC solar cells, and 76% for EPC solar cells. The higher FF in SPC solar cells suggests improved charge carrier collection efficiency. In terms of photoelectric conversion efficiency, SPC solar cells demonstrate a 10.6% increase, while EPC solar cells show a 7.7% increase. These improvements indicate that the incorporation of PCs in the solar cells enhances their ability to convert light into electrical energy. These findings highlight the potential of photonic crystals engineering for enhancing the performance of solar cells.

Surface-Enhanced Raman Spectroscopy (SERS) Substrates Based on Photonic Crystal Embedded Bi-Metallic Nanoparticles for Leptospiral DNA Detection.

Leptospirosis is an acute bacterial febrile disease affecting humans and animals in many tropical and subtropical countries. This work presents an optimization of surface-enhanced Raman spectroscopy (SERS) substrates to probe vibrational spectroscopic detail from Leptospira deoxyribonucleic acid (DNA). The pathogenic gene of LipL32 was used as a biomarker. The SERS substrates were based on a photonic crystal (PC) structure embedded with bi-metallic gold and silver nanoparticles (PC@AuAg NPs). The localized plasmonic resonance of AuAg NPs was coupled to the Raman modes of the target through SERS interaction. Prior to detection, the AuAg NPs were functionalized with chemical linkers to facilitate specific conjugation between metallic surfaces and DNA biomolecules. The immobilization and hybridization of probe DNA to their complementary target DNA (cDNA) created duplex formation for detection. The configuration was also tested with non-complementary DNA to verify detection specificity. Prominent SERS peaks were recorded, and the characteristic intensity decreased after cDNA hybridization due to less base interaction after complementary pairing. Distinct SERS behavior from the negative control test was also observed in non-complementary interaction. The configuration is highly attractive and can be potentially extended for sensitive and label-free detection of leptospiral DNA, paving the way for alternative diagnosis of leptospirosis.

Three-dimensional energy-controllable focal spot array with extended depth of focus created by pure phase modulation

To produce a three-dimensional (3D) energy-controllable focal spot array with an extended depth of focus (EDOF), we propose a pure phase modulation that combines a two-dimensional (2D) pure phase sinusoidal grating (2D PSG) and a light sword optical element (LSOE). The intensity distribution in the 3D focal field is achieved by both simulation and experiment, exhibiting high energy controllability and EDOF. Additionally, the position of the maximum intensity value of any focusing spot exhibits a rotation characteristic, further indicating that the EDOF can be continuously extended. The transverse spacing between adjacent foci, the shape of the focusing spot, and the intensity distribution are achieved in comparison between simulations and experiments, showing good conformity in two situations of f1/f=10% and 20%. Our proposed method paves a new way to produce the 3D energy-controllable focal spot array with EDOF, laying a solid foundation for its application in various fields, such as 3D photonic crystal structures, 3D luminescence, and 3D optical sensing.

Dynamic laser protection window based on a topological state photonic crystal of a nonlinear LiNbO3 interface.

The accelerated advancement of high-energy laser technology has resulted in an increased necessity for multifunctional laser protection. Herein, we present an investigation into a static visible and dynamic 1064 nm laser protection window. Through studying the photonic crystal energy band structure and topological interface state properties, both 66.49% average visible light transmittance and 84.01% low-energy 1064 nm laser transmittance are achieved. The combination of a large third-order nonlinear effect of LiNbO3 and strong light field localization of a topological interface state enables a 27.54 mJ/cm2 protection threshold below that of traditional materials. This study offers what we believe to be new avenues for the development of multifunctional optical windows and novel optical elements.

Sensitive One-Dimensional Photonic Crystal Refractometric Temperature Sensor with Central Superconducting Layer

This work proposes a sensitive low-temperature sensor based on the refractive index (RI) method. It uses a one-dimensional (1D) photonic crystal (PC) structure. The proposed sensor design consists of a bilayer stack of dielectric and superconductor materials. YaBa2Cu3O7 is the superconductor utilized in this case, and we consider air to be the dielectric material. The RI of air doesn’t change much with the temperature, especially compared to the superconductor material. YaBa2Cu3O7 is a superconductor that is ideal for temperature sensing applications because of its temperature-dependent RI. The sensing temperature range for the proposed sensor is 35–70[Formula: see text]K. The crucial structural factors have been precisely adjusted to increase sensing performance. Based on our knowledge, this is done to increase the sensor’s efficiency to levels that are higher than anything previously reported in the literature. Results show that the designed structure achieves an impressive RI sensitivity of 821.53[Formula: see text]nm/RIU and a temperature sensitivity of 3[Formula: see text]nm/K. This sensor could be very useful for medical applications for the detection of low temperatures.

A two-stage detection methodology for thyroid cancer using photonic crystal: Logistic regression and artificial neural networks

Cancer remains a significant health concern affecting many people globally. Recognizing the importance of early identification and treatment of thyroid cancer, we have developed a novel detection method utilizing supervised Machine Learning (ML) techniques, specifically Logistic Regression (LOR) and Artificial Neural Networks (ANN). Our approach leverages Photonic Crystal (PhC) sensors to detect thyroid cancer. Thyroid cancer affects the thyroid gland, which is responsible for regulating the body's growth and metabolism through hormone production. The incidence of thyroid cancer is increasing worldwide, making early and accurate diagnosis crucial for improving patient outcomes. Current detection methods like fine-needle aspiration biopsy and ultrasound have limitations in terms of accuracy, invasiveness, and cost. Thus, we propose the use of PhC sensors, which can detect changes in the Refractive Index (RI) of biological tissues caused by cancerous cells. In our two-stage detection methodology, the first phase uses LOR to classify specimens as benign or malignant based on data from PhC sensors. The second phase employs ANNs to further classify the malignant samples into papillary, follicular, medullary, or anaplastic thyroid cancer. Our research demonstrates the effectiveness of PhC sensors as a cutting-edge method for thyroid cancer detection. We conducted simulations using MEEP with a PhC structure size of 26×24. Subsequently, we compiled a comprehensive dataset through meticulous data sampling and analysis. This dataset was then utilized to implement supervised ML methods, such as LOR and ANNs, for non-invasive thyroid cancer detection. The LOR model achieved an accuracy of 91 %, a sensitivity of 93 %, a precision of 94 %, an F1 score of 90 %, and a specificity of 89 %. Meanwhile, the ANN model attained an accuracy of 82 %, a sensitivity of 77 %, a precision of 85 %, an F1 score of 81 %, and a specificity of 87 %. These results underscore the potential of our innovative approach to significantly enhance the diagnosis and treatment of thyroid cancer.

Fabrication of PBAT Membranes with High Separation Accuracy Based on Inverse-Opal-Structural Photonic Crystals.

Membrane technology is one of the most effective ways to cope with the filtration and separation. However, most polymer membranes are not uniform in pore size and have wide pore size distributions and low porosities, which restrict their application. A high-porosity homogeneous membrane with high filtration accuracy is an effective solution. Photonic crystals (PCs) with an inverse-opal (IO) structure provide a new way for preparing high-porosity homogeneous porous membranes. In this study, a rapid shear-induced assembly method for preparing biodegradable poly(butylene adipate-co-terephthalate) (PBAT) membranes based on PCs with an IO structure was proposed, and the design principles of the IO-structured PBAT membrane were investigated. Moreover, the effects of polymer solution concentrations, solvent evaporation temperature, and SiO2/PBAT mass ratio on the SiO2/PBAT PC structure, formation mechanism of shear-induced assembly, and the filtering efficiency of resultant PBAT membranes for solid-liquid separation were investigated. The study underscored the point that when the polymer concentration is in the range of 15-20 wt % and the drying temperature is at 80 °C, as the SiO2-to-PBAT mass ratio increases, the pore of the membrane increases, the porosity is as high as to 84.11%, and pure water flux is up to 756.19 L m-2 h-1. After five cycles, the rejection rate of PBAT membranes for the contaminant still reached more than 99%. This study proposes a simple and rapid method for constructing an IO-structured membrane that is expected to address challenges encountered in achieving efficient and high-precision separation.

Improving the label-free rapid semi-quantification of E.coli by AgNPs-decorated hydrogel inverse opal photonic crystals

Using photonic crystal materials for colorimetric sensing, the influences of structure and composition on the photonic bandgap (PBG) of materials are always vital to detection. In this work, the effects of pores in the structure of polyethylene diacrylate-based inverse opal photonic crystal (PEGDA-based IOPC) and the concentration of silver nanoparticles (AgNPs) used for decoration of the IOPC by chemical reaction on the shift of PBG center (λrp) have been studied for rapid semi-quantification of Escherichia coli (E. coli). We found that pores in the structure of PEGDA-based IOPC significantly increased the amount of AgNPs attached to this material compared with the structure created by the ordered self-assembly of spherical SiO2 particles of the parent template, leading to a pronounced red-shift of λrp. At the concentration of 20 µg/L AgNPs (CAgNPs) used for decoration, the shift of λrp reached 80 nm due to the increase in the average refractive index (naver.) of the material. It thus enabled us to observe changes in the color of the reflected light with the naked eye. In addition, since the increase in the concentration of E.coli (CE.coli) also caused a red-shift of the λrp, the CAgNPs, thus, could be reduced but still give a sufficiently strong shift of λrp to detect E.coli at a high level. The spectral position of the reflectance peak changed from green to red with increasing the CE.coli from 50 cfu/mL to 106 cfu/mL at the CAgNPs = 10 µg/L. These results indicated the potential application of AgNPs decorated PEGDA-based IOPC in rapid semi-quantification of E.coli by the naked eye.

Defect engineering in organic semiconductor based metal-dielectric photonic crystals

We investigate the band structure of metal-dielectric photonic crystals comprising stacked organic semiconductor microcavities with silver metal mirrors incorporating crystal defects: individual unit cells with aperiodic dimensionality. Both transfer matrix simulation and experimental verification are performed to investigate the impact on the photonic band structure as a single cavity is varied in size. The resulting mid-gap defect states are shown to hybridize with a photonic band at certain resonant dimensions. The resonance of the defect cavity affects the transmittance of light through the device, disrupting or enhancing the coupling between otherwise resonant cavities. We outline potential applications for defect engineering of these devices through controlled manipulation of the transmission spectrum.

Engine Oil Quality Monitoring Using a GaAs-Based Tribo-Photonic Sensor

The study aims to design a photonic crystal-based oil sensor that continuously monitors engine oil, enabling faster detection of oil degradation stages compared to existing technologies such as microscopic techniques, spectroscopy, and field experience. GaAs composite rods featuring an air backdrop lattice serve as the fundamental components of the photonic crystal structure utilized in the proposed sensor. The FDTD approaches allow optical and dispersion properties to be examined in a label-free sensing environment. The sensing mechanism relies on the change in refractive index leading to a shift in the resonant wavelength. Opti-FDTD software has been used to design and simulate the sensor. The results show that the tribo-photonic sensor has a high sensitivity of 590.49 nm/RIU, a high Q-factor of 9332.03, a low detection limit (δ) of 341.17 × 10-6 RIU, a high FOM of 2931.01 RIU-1, and a compact area of 47.63 μm2.

Consistent color generation from polycrystalline particles constructed with silica nanospheres

The strict periodic structure of photonic crystals induces photonic bandgaps, leading to reflection of light at specific frequencies and angles of incidence. However, the structural color arising from constructive interference exhibit iridescence, varying with viewing angles, thereby restricting their practical use as substitutes for pigments. Color perception is a psychological rather than a physical phenomenon. For example, in raster images, proportionally mixed spectral colors are perceived in brain as a novel color beyond the monochromatic. Inspired by this, photonic crystals are assembled into polycrystalline photonic balls, where surface structures exhibit radial symmetry around the ball center. Although the constructive reflected lights in a unified direction from these photonic crystals have different frequencies, the polychromatic from the ball remain consist as the viewing angle is varying. For the diameter of the ball is smaller than the eye's spatial resolution, its color remains stable regardless of viewing angles. Then, the color of the ball can be tuned by adjusting the interplanar spacing of the photonic crystals. Six consistent-color polycrystalline photonic balls are fabricated in this paper, which hold potential as pixels in future coloration applications.

Slow-light-driven photocatalytic CO2 reduction to CH4 mediated by photonic crystal Graphdiyne-Cu/ZnO Z-scheme system

Developing photocatalysts with high activity and selectivity remains a significant challenge in the field of CO2 photoreduction for producing valuable chemical or fuel products under mild conditions. Herein, photonic crystal (PC) GDY-Cu/ZnO was constructed through the in-situ induced growth of graphdiyne (GDY) on PC Cu/ZnO surface via H2-reduction for efficient photoreduction of CO2 to CH4. With the aid of photonic crystal structure, PC GDY-Cu/ZnO exhibits a distinctive red-edge slow light region which can significantly improve the utilization efficiency of visible light and intensify photo-catalysis. Additionally, the formed all-solid-state Z-scheme system efficiently accelerates photoelectron migration, facilitating e-/h+ separation. Thirdly, the surface GDY, along with the enrich oxygen vacancies generated during H2 reduction, enhances the adsorption and activation toward CO2 and H2O on PC GDY-Cu/ZnO interface. In consequence, PC GDY-Cu/ZnO demonstrates highly photocatalytic conversion of CO2 to CH4, achieving a CH4 yield of 33.67 μmol·g−1·h−1 with 93.3 % selectivity via slow-light-driven photocatalysis CO2 reduction. This work provides an efficient strategy to modify ZnO for the efficient photoreduction of CO2 to CH4.