Photonic Crystal Structure Research Articles

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 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 under water, 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 micro scale. The second part describes the fabrication strategies for constructing mechanochromic colloidal 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 of a High Q-Factor Label-Free Optical Biosensor Based on a Photonic Crystal Coupled Cavity Waveguide.

In recent years, there has been a significant increase in research into silicon-based on-chip sensing. In this paper, a coupled cavity waveguide (CCW) based on a slab photonic crystal structure was designed for use as a label-free biosensor. The photonic crystal consisted of holes arranged in a triangular lattice. The incorporation of defects can be used to design sensor devices, which are highly sensitive to even slight alterations in the refractive index with a small quantity of analyte. The plane wave expansion method (PWE) was used to study the dispersion and profile of the CCW modes, and the finite difference time domain (FDTD) technique was used to study the transmission spectrum, quality factor, and sensitivity. We present an analysis of adiabatically coupling light into a coupled cavity waveguide. The results of the simulation indicated that a sensitivity of 203 nm/RIU and a quality factor of 13,360 could be achieved when the refractive indices were in the range of 1.33 to 1.55.

Design Simulation of Circular Photonic Crystal Structures for the Development of Biomedical Sensor Based on Finite Difference Method

Optical analysis of a circular photonic crystal structure consisting of a metal-dielectric layer and a defect layer sandwiched between two dielectric layers has been carried out using the Finite Difference Frequency Domain (FDFD) method and the Finite Difference Time Domain (FDTD) method. The FDTD method can describe the propagation of electromagnetic waves on the structure at any time, while the FDFD method can describe the characteristics of the wave interaction with the structure in a steady state. We observed strong resonances at certain wavelengths when using three different dielectric materials: , , and . The simulation results show a change in the resonance peak in the sensing material in the form of normal blood and blood-containing glucose in the defect layer for concentration: . The use of three different dielectric materials produces different sensitivity values. The highest sensitivity value when using material that produces a sensitivity value of at the refractive index intervals . The simulation results can be used to build biomedical sensors that measure blood sugar levels.

Low-threshold single-mode nanowire array flat-band photonic-crystal surface-emitting lasers with high-reflectivity bottom mirrors.

A Si-based nanowire array photonic-crystal surface-emitting laser based on a flat band is designed and simulated. By introducing an air gap between the nanowire and substrate, the bottom reflectivity is significantly enhanced, resulting in much lower threshold and smaller cutoff diameter. Through adjusting the lattice constant (the distance between neighboring nanowires) and nanowire diameter, a photonic crystal structure with a flat band is achieved, in which strong interaction between light and matter occurs in the flat band mode. For the device with a small size, single-mode lasing is obtained with a side-mode suppression ratio of 21 dB, high quality factor of 3940, low threshold gain of 624 cm-1, and small beam divergency angle of ∼7.5°. This work may pave the way for the development of high-performance Si-based surface-emitting nanolasers and high-density photonic integrated circuits.

Programmable Shaping of Femtosecond Pulses Using a One-Dimensional Photonic Crystal with Continuous Spatial Modulation of the Refractive Index

An algorithm for constructing the structure of a one-dimensional photonic crystal, which forms a femtosecond pulse of an arbitrary given shape when reflecting a Gaussian pulse, is developed theoretically. The method is illustrated by the example of a rectangular pulse. Examples for simple pulse shapes are given, the influence of optical absorption is evaluated, and a method for its compensation is proposed.

Angular dependence of photonic band gap and omni-directional reflection in one-dimensional photonic crystal applied to a thermophotovoltaic device

In this work, we present a theoretical study and a numerical simulation on omnidirectional reflection in one-dimensional photonic crystal structures for a thermophotovoltaic device. The optical properties are determined using the transfer matrix method. The results show that the angular dependence of photonic bandgaps depends on refractive index contrast and, polarization. However, for both TE and TM polarization, a reflectivity peak with 100% reflectivity is observed. The Te/SiO2 structure is the one with the largest bandwidth of omnidirectional photonic band gap compared with the TiO2/SiO2 and Si/SiO2 structures. The results also show that by designing a giant birefringent optical the Brewster’s angle allows angle the control at any angle for both TE and TM mode.

Effect of sintering temperature on the dielectric properties of 3D‐printed alumina (Al2O3) in the W‐band

AbstractThis contribution discusses the impact of sintering temperatures on dielectric properties of 3D‐printed alumina (Al2O3) in the W‐band, by evaluating high quality factor (−Q) resonators integrated in a 2D photonic crystal structure. By varying the sintering temperature of the lithography‐based ceramic manufactured (LCM) samples, the microstructure of the material can be defined, which has a direct impact on the dielectric permittivity and material losses. Using a highly accurate photonic crystal structure, with a dimensional variation below 2% from print to print, an accurate extraction and evaluation of the dielectric material properties could be achieved. The relative permittivity of the alumina was tuned from 4.4 at 1250°C to 9.2 at 1650°C, whereas the observed change in dielectric losses was moderate. The maximum in observed dielectric loss for samples sintered at the lowest evaluated temperature, only yields an average value of 30 × 10−4. This demonstrates the versatility of the LCM technology for mm‐ and sub‐mm‐wave applications and its possibilities for material tuneability.

Study on the subjective brightness of photonic crystal structural colored wood products

ABSTRACT Photonic crystal structural color is a novel method in the field of colored coating on the surface of wood products. However, the subjective brightness of photonic crystal structural colored wood products under different color temperature light sources has not been studied. In this study, poly(styrene-methyl methacrylate-acrylic acid) latex microspheres with different diameters were used to construct photonic crystal coatings on wood surface. The subjective brightness psychological quantity under different color temperature light sources was obtained. Combined with the optical properties of the coatings, the correlation between the physical optical properties of the photonic crystal coating, the color temperature of the light source and the subjective brightness of the coating was obtained. The photonic crystal coating in the near red visible light wavelength range had higher subjective brightness under low color temperature light source, and coating in the near purple visible light wavelength range had higher subjective brightness under high color temperature light source. The subjective brightness of the photonic crystal coating was very closely related to the light source color temperature and closely related to the reflectivity of the coating. This study expands the research on the optical properties of photonic crystal structure colored wood products.

A neural networks approach for designing compact all-optical photonic crystal based AND logic gate

Abstract This paper introduces a new method for creating an all-optical AND gate by utilizing a two-dimensional photonic crystal configuration for the first time. This gate design is intended for applications in optical computing and all-optical logic, offering the potential for rapid computation and parallel processing. The described gate is characterized by its compact dimensions and comprises two inputs and a single output. The high and low logic states are defined based on power values, where logic 0 corresponds to low power and logic 1 corresponds to high power emitted from the light source. To enhance the design process, artificial neural networks (ANNs) are utilized. ANNs offer a powerful tool for optimizing and fine-tuning the photonic crystal structure parameters to achieve the desired logic functionality. With the help of the applied ANNs, the design process is eased and high performance is achieved for the proposed photonic crystal structure. By integrating ANNs into the design process, this research opens up new possibilities for advancing the field of photonic logic circuits. Combining photonic crystals and ANN optimization provides a powerful approach to designing complex and efficient optical computing systems. The results show that the obtained power values are high for 1 logic state and low for the 0 logic state, which verifies the AND gate accuracy table. The achieved accurate results verify the validity of the proposed approach for achieving precise and reliable all-optical logic operations.

A temperature sensor based on Si/PS/SiO2 photonic crystals

The present research deals with the extremely sensitive temperature-sensing capabilities of defective one-dimensional photonic crystal structures (Si/PS/SiO2). The proposed structure is realized by putting a defective layer of material silicon Dioxide (SiO2) in the middle of a structure consisting of alternating layers of silicon (Si) and porous silica (PS). The transfer matrix method has been employed to examine the transmission characteristics of the proposed defective one-dimensional photonic crystal in addition to MATLAB software. The transmission spectra of the proposed structure in the visible light domain are computed throughout a temperature range of 25–900 °C, and we study the thermal properties related to the defective mode. Additionally, the impacts of changing the defect layer's thickness are examined. Due to the effects of thermal expansion and the thermo-optical coefficient, the defect mode varies significantly as the temperature increases. Our investigation shows that the proposed structure considerably impacts the transmission intensity of the defective mode. The theoretically obtained numeric values of the quality factor and sensitivity are 2216.6 and 0.085 nm/°C, respectively. The challenges presented by conventional temperature sensors could be overcome by the suggested defective photonic crystal sensor. These results are enough to support our claim that the present design can be used as an ultra-sensitive temperature sensor.

Defect modes in defective one dimensional parity-time symmetric photonic crystal

The introduction of defect layers into one-dimensional parity-time (PT) symmetric photonic crystals gives rise to resonances within the photonic bandgaps. These resonances can be effectively explained by our generalized temporal coupled mode theory. The scattering properties and dispersion relation of defect modes exhibit distinct characteristics compared to conventional one-dimensional Hermitian photonic crystals with defect layers. By tuning the non-Hermiticity or other model parameters, the modulus of the generalized decay rate can be reduced, consequently, the electric field concentrated within the defect layer strengthens. This arises due to the unique band structure of one-dimensional PT-symmetric photonic crystals, which differs significantly from that of traditional one-dimensional Hermitian photonic crystals. Furthermore, the interaction between multiple resonances is investigated through the introduction of multiple defect layers. Our study not only provides insights into resonance phenomena in defective non-Hermitian systems but also contributes to the design of relevant optical resonance devices.

Operando Color-Coding of Reversible Lithiation and Cycle Life in Batteries Using Photonic Crystal Materials

Innovative new materials are consistently emerging as electrode candidates from lithium-ion and emerging alternative battery research, promising high energy densities and high-rate capabilities. Understanding potential structural changes, morphology evolution, degradation mechanisms and side reactions during lithiation is important for designing, optimizing and assessing aspiring electrode materials. In-situ and operando analysis techniques provide a means to investigate these material properties under realistic operating conditions. Here, we demonstrate operando spectroscopic sensing using photonic crystal-structured electrodes that uses the optical transmission spectrum to monitor changes to the state of charge or discharge during lithiation, and the change to electrode structure, in real-time. Photonic crystals possess a signature optical response, with a photonic bandgap (or stopband) presenting as a structural color reflection from the material. We leverage the presence of this photonic stopband, alongside its intricate relationship to the electrode structure and material phase, to correlate electrode lithiation with changes to the optical spectrum during operation. We explore the optical and electrochemical behavior of a TiO2 anode in a lithium-ion battery, structured as a photonic crystal. The operando optical sensing demonstrated here is versatile and applicable to a wide range of electrochemical electrode material candidates when structured with ordered porosity akin to a photonic crystal structure.

Recent progress in low‐swellable polymer‐based smart photonic crystal sensors

AbstractLow‐swelling polymers (LSPs) generally refer to materials with a low solvent absorption ratio or volume expansion rate at swelling equilibrium. LSPs with exceptional responsiveness could be upgraded to smart sensors with structural color self‐reporting by bridging photonic crystals (PCs). Based on the regulation of swelling to effective refractive index, lattice spacing, the order‐disorder arrangement of nanostructures, and incident/detection angle, the structural color feedback of smart photonic crystal sensors (SPCSs) can quantitatively and visually reveal the stimulus, which greatly promotes the interdisciplinary development of nanophotonic technology in the fields of chemical engineering, materials science, engineering mechanics, biomedicine, environmental engineering, etc. Herein, to clarify the role of the photonic structures and polymer molecules in high‐performance SPCSs, LSP‐based SPCSs are summarized and discussed, including general swelling mechanisms, color change strategies, structural design, and typical functional applications. It aims to figure out the combination rule between PC structures and LSPs, optimize the design of PC structures, and expound the corresponding structural color sensing mechanisms, inspiring the fabrication of next‐generation SPCSs. Finally, perspectives on future structural design and sensing applications are also presented. It is believed that SPCSs are multifunctional nanophotonic tools for the interdisciplinary development of numerous engineering fields in the future.

Enhanced second-harmonic generation in a photonic crystal waveguide-coupled nanocavity using a wavelength-selective reflector

Photonic crystal waveguide-coupled photonic nanocavities are promising to develop integrated nonlinear nanophotonic devices because of their strong nonlinear optical process in cavities with high quality (Q) factors and small modal volume, multiple-wavelength-channel operation, and efficient and highly dense integration with other optical components. However, the intrinsic features of the standing-wave mode in the photonic crystal resonant cavity cause some waveguided light to pass through the nanocavity without coupling, which remains a significant challenge in achieving high nonlinear optical efficiency in integrated nanophotonic devices. To feed back the uncoupled light into the nanocavity and enhance the nonlinear optical efficiency in a photonic crystal waveguide-coupled nanocavity, we designed and fabricated a wavelength-selective reflector based on a silicon carbide two-dimensional photonic crystal structure and experimentally demonstrated the significant enhancement of second harmonic generation (SHG) using the reflector. The findings suggest that the reflector increases the electric field intensity in the nanocavity and improves Q-matching between the nanocavity and the waveguide. These two effects of the reflector significantly enhance the SHG efficiency by 11.5 compared to that without a reflector. The experimental results agree well with the calculation results obtained using coupled-mode theory. Our study paves the way for developing efficient nonlinear optical devices for high-density integrated nanophotonics and quantum applications.

Band structure optimization of superconducting photonic crystals based on transmission spectrum calculation

The design of photonic crystals using novel materials is of great significance for the construction of high-performance, next-generation photonic crystal devices. We propose a universal Band structure-Transmission optimization-Band structure method based on moving asymptotic (MMA) method, which can be widely applied to photonic crystal structures. In this paper, we use the method to optimize the band structure of high temperature superconducting photonic crystal, and obtain a wider photonic bandgap and better band flatness in a specific frequency band. This method avoids the disadvantages of traditional scanning methods such as low efficiency and high resource consumption, allows multi-parameter optimization, and improves the accuracy and effectiveness of band modulation based on the iterative process of numerical calculation. The study provides some insights for the design of novel wide-bandgap optical devices.

Annular one-dimensional photonic crystals for salinity sensing

The use of annular one-dimensional (1D) photonic crystals (PCs) for salinity sensing is studied in this research. Annular 1D-PCs provide small and integrated structures that facilitate the creation of portable and miniaturized sensor equipment appropriate for field use. In order to generate annular 1D-PCs, the research explores the finite element method (FEM) simulation technique utilizing the COMSOL Multiphysics approach, highlighting the significance of exact control over layer thickness and uniformity. Furthermore, we construct a 1D annular PCs structure in the form {(AB)}^{N}, where A is silicon (Si) and B is silicon dioxide ({SiO}_{2}) of 40 nm and 70 nm, respectively, with a number of periods equal to 9. By incorporating a central defect layer of saline water (220 nm thickness), the sensor achieves optimum performance at normal incidence with a sensitivity (S) of 782 (nm/RIU), a quality factor (Q) of 10.22, and a figure of merit (FOM) of 12.6 {RIU}^{-1}. The design that is suggested has several advantages over past work on planners and annular 1D-PCs, including ease of implementation, performance at normal incidence, and high sensitivity.

THz wave Mux/DeMux operation using bearded-type topological photonic crystal waveguide structure

Abstract Terahertz (THz)wave wireless communication technologies have been developed to increase transmission capacity in 6G communications. Although the realization of integrated waveguides in THz wave transmitters and receivers is essential, bending loss in THz waveguides is important as well. This study investigated a THz waveguide based on a valley photonic crystal (VPC) structure. We numerically investigated a THz waveguide with sharp bending and Mux/DeMux filters based on the oblique rectangular resonator of a bearded-type VPC waveguide.

Improvement on solar selective absorption properties of anodic aluminum oxide photonic crystal films by electrodeposition of silver

Solar selective absorption films based on anodic aluminum oxide (AAO) photonic crystals were prepared by an anodization under periodic current-pulses, subsequently with an alternating current electrodeposition of Co and Ag in sequence. The phase structure, microstructure, and solar selective absorption properties of the Co–Ag electrodeposited film were investigated in comparison with a Co electrodeposited counterpart. Moreover, the stability of the properties against thermal annealing was examined for the two films. A one-dimensional photonic crystal structure was verified for the AAO part in both films, with the first-order photonic bandgap occurring at around 4 μm, while the metals were confirmed to be deposited at the bottom of the AAO part in the form of nanoparticles. For the Co–Ag electrodeposited film, the Ag nanoparticles were deposited over those of Co. The Ag electrodeposition not only was contributive to the solar selective absorption properties, but also substantially improved the stability of the properties against thermal annealing. The Co–Ag electrodeposited film exhibited an infrared emissivity of 0.12, a solar absorptivity of 0.94, and a spectral selectivity of 7.83 before experiencing thermal annealing, while retained a decent spectral selectivity of 6.00 after being annealed in air at 300 °C for 24 h.

Performance analysis of heterostructure-based topological nanophotonic sensor

In this manuscript, a heterostructure-based topological nanophotonic structure is proposed for improved sensing performance. The topological effect is realized by connecting two dissimilar one-dimensional photonic crystal structures having overlapped photonic bandgaps. The structural parameters are optimized to regulate and alter the dispersion characteristics, which results in the opposite Zak phases. This demonstrates a robust topologsical interface state excitation at a 1737 nm operating wavelength. Further, a topological cavity structure having resonance mode at 1659 nm is formed by replacing the interface layers with a defect layer. The mode excitation is confirmed by analyzing the electric field confinement at the interface. The sensing capability of the structure is analytically evaluated by infiltrating different analytes within the cavity. The analytical results demonstrate the device’s average sensitivity of around 774 nm/Refractive index unit (RIU) along with an average high Q-factor and figure of merit of around 5.2 × 104 and 2.6234 × 104 RIU−1, respectively. Because of the higher interface mode field confinement, the proposed structure exhibits a 92% higher sensitivity, 98% improved Quality factor, 206% improvement in figure of merit, and 86% higher interface field confinement than conventional Fabry–Perot resonator structures. Thus, the proposed topological cavity structure shows its broad sensing ability (Refractive Index: 1.3–1.6) along with a low-cost, simple fabrication and characterization process, promoting the development of highly sensitive planner nanophotonic devices.

A low-threshold single-mode higher-order topological photonic crystal nanowire array laser

A higher-order topological photonic crystal GaAs/AlGaAs/GaAs nanowire array laser based on 0D corner modes is proposed and analyzed. The structure is composed of a nanowire trivial photonic crystal sandwiched by two topological photonic crystals. Compared with the conventional deformed honeycomb lattice photonic crystal structure, an additional mode selection mechanism is introduced by adjusting the coupling strength of topological cavities formed at two topological interfaces. By optimizing the structure parameters, a large side-mode suppression ratio of 24 dB and a high-quality factor of 7935 are obtained. Due to the strong mode confinement, lasing is achievable at an ultrasmall diameter of 86 nm, with a high confinement factor of 7.96 and low threshold gain of 230 cm−1. Moreover, the laser exhibits a small beam divergence of 6.6°. This work may pave a way for the development of low-threshold single-mode miniaturized lasers.