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Recently, nanoscale thermometry has attracted extensive attention. Here, we present an innovative approach to enhance the sensitivity of upconversion nanoparticles for thermometry through near-field manipulation. This method involves a composite structure consisting of photonic crystals and upconversion nanoparticles, with the near-field of the nanoparticles manipulated by tuning the absorption of the photonic crystals. The fluorescence intensity ratio (540nm/520 nm) of 4H 11/2 and4S 3/2 states of upconversion nanoparticles doped with Er3+ ions is sensitive to temperature change and employed as a temperature indicator that satisfies Boltzmann thermal equilibrium. The composite structure exhibited a relative thermometry sensitivity of 21.9 × 10−3 K−1 at 298 K, representing a significant improvement over pure core-shell upconversion nanoparticles with a 63.43% increase in relative sensitivity and a 675% increase in absolute sensitivity. This finding demonstrates the potential of our approach for advancing nanoscale thermometry. [ABSTRACT FROM AUTHOR]

Types of brain lesions, tumors, and cancers are still considered deadly. They require accurate and expensive detecting, diagnosing, and treatment methods. This work presents a biomedical photonic-based sensor that can detect and distinguish accurately between normal and abnormal brain tissues. The abnormal ones consist of lesions, tumors, and cancerous tissues. The designed sensor detects these types with acceptable sensitivity and high-quality factor compared to other photonic-based detecting techniques. The proposed sensor achieves a sensitivity of 1332 nm/RIU, a very low detection limit of 9.08 × 10-6, and an ultra-high quality factor of 16254. Ultra-compactness and the ability to fabricate with today's technology are novel features in the proposed design. An abbreviated review of non-optical detection techniques is presented. An in-depth comparison between this work and related photonic-based recent literature is drawn to validate the efficacy and authenticity of the proposed design. [ABSTRACT FROM AUTHOR]

A new design for chiral photonic cellulose nanocrystal films was developed by co-assembling lanthanide-doped nanorods (NRs) into chiral cellulose nanocrystals, in which the photonic band gap (PBG) could be tuned in the visible range by changing the mass fraction of flexible agents, such as polyvinyl alcohol (PVA) and ethylene glycol (EG). Due to the PBG effect, the luminescence modulation in such nanocrystal films had been realized. The down-conversion luminescence from NaGd 30 Y 60 F 4 :5%Tb3+, 5%Eu3+ NRs and up-conversion luminescence from NaGd 40 Y 40 F 4 :18%Yb3+, 2%Er3+ NRs could be enhanced by 28 % and 18 % respectively, on account of the band edge effect. The luminescence would be inhibited when the luminescence overlapped with the stop band of the PBG. These results implied that the biocompatible photonic cellulose nanocrystal films are ideally suited for applications in optical coding, optical resonators and biocompatible lasers. [Display omitted] • Chiral photonic cellulose nanocrystal films were co-assemblied by lanthanide-doped nanorods and cellulose nanocrystals • The photonic band gap (PBG) of the films can be tuned in the visible range by changing the amount of the flexible agents • The one-dimensional photonic crystal structure (1D PCs) of the films enables the luminescence regulation. [ABSTRACT FROM AUTHOR]

To address the lengthy cycles, complex operations, high costs, and insufficient sensitivity of biomarker detection in traditional biological control agents, photonic crystal treated with PEI was developed for highly sensitive detection of Sclerotinia sclerotiorum microbial spores. By incorporating gelatin molecules, photonic crystal is endowed with excellent photothermal stability and high stability in aqueous solutions. The photonic crystal surface is conferred a positive charge by PEI, which can be used to enhance the adsorption of spores. Efficient enrichment of Sclerotinia sclerotiorum and Purpureocillium lilacinum spores is achieved, with coefficients of determination 0.963 and 0.971, respectively. The detection range is from 102 to 106 spores/ml, and the photonic crystal exhibited good reusability. The prepared photonic crystal enables rapid, non-destructive, and accurate quantitative detection of microbial spores. • PEI-Modified Photonic Crystal Microfluidic Chip For Highly Sensitive Detection of Microbial Spores was implemented. • The detection range was from 102 to 106 spores/ml, and the surface exhibited good reusability after 10 cycles. • Within 20 min, efficient enrichment of Sclerotinia sclerotiorum and Cladosporium cladosporioides spores was achieved, with corresponding wavelength shifts of 79 nm and 35 nm, and coefficients of determination (R2) are 0.963 and 0.971, respectively. [ABSTRACT FROM AUTHOR]

A novel superparamagnetic photonic crystal DNA probe (Fe 3 O 4 @SiO 2 @amino@DNA SPC) was developed to enable rapid visual detection of Hg2+. This unique photonic crystal (PC) was synthesized by combining superparamagnetic nanospheres with DNA probes. The DNA probe, rich in thymine (T), detects mercury ions through base mismatch, resulting in the formation of T–Hg2+–T loop hairpin structures. With the binding of Hg2+ to the probe attached to superparamagnetic nanospheres, the PC structure assembled by these nanospheres, formed by the magnetic field, was changed. This change enhanced the reflection intensity; it could be quantified using a fiber optic spectrometer and was visible to the naked eye. The Fe 3 O 4 @SiO 2 @amino@DNA SPC, specific to Hg2+, exhibited a reflection peak at 679 nm, which intensified with increasing Hg2+ concentration. The reflection intensity increased by 132.58 a.u., and the PC color shifted from red to yellow as the Hg2+ concentration increased from 0.1 μg/L to 1 mg/L. • A superparamagnetic photonic crystal sensing material with DNA probes is fabricated. • Combination of photonic crystal, superparamagnetic nanospheres, and DNA probes. • The rapid real-time detection of Hg2+ in water with naked-eye color change results. • Successfully introduce a unique DNA probe on superparamagnetic nanospheres. • Mitigate the challenge of modifying biological macromolecules on photonic crystal. [ABSTRACT FROM AUTHOR]

A two-dimensional (2D) photonic crystal (PC) based biosensor was developed and studied to detect albumin and urea levels in patients with proteinuria. Rhombic ring resonator structures are built with the help of FDTD (Finite Difference Time Domain). After the fields are computed using the 2D-FDTD approach, the normalized transmission spectra are produced by applying the Fast Fourier Transform (FFT) to them. The full width at half maximum (FWHM), Quality factor (Q-factor), Sensitivity, Figure of Merit (FOM), and Limit of Detection (LOD) are 15,466.5, 110 nm/RIU, 0.12 nm, 1100 RIU − 1 and 54. 34 X 10 − 6 RIU respectively, when the resonant wavelength is 1546 nm. The novelty of this the project lies in combining 2D photonic crystal, innovative rhombic ring resonator design and high-performance parameters. The achieved values are notably high, which is a novel achievement in the field of biosensing. The project aims to contribute to the field of biosensors and provide a potential tool for healthcare professionals to monitor diabetes, proteinuria, kidney function and overall health. [ABSTRACT FROM AUTHOR]

[Display omitted] • An MIPCH colourimetric sensor is developed for the selective and sensitive detection of AA. • The rebinding of the AA analyte to the MIPCH causes the hydrogel to swell, leading to a significant redshift in its structural colour. • The change in structural colour serves as an easily observable indication of the sensor response. • The AA-MIPCH sensor exhibits a low detection limit and high level of selectivity for detecting AA molecules. • Employed CNN-based deep learning algorithm to quantitatively predict the concentration of the target molecule. Molecular imprinted photonic crystal hydrogel (MICPH) sensors have gained recognition as an efficient platform for selectively detecting analyte molecules. In the present work, we report the development and implementation of a colorimetric sensor based on MIPCH for the selective detection of Ascorbic acid (AA). The fabrication process of the MIPCH sensor involves the photo-polymerization of a hydrogel precursor solution containing AA molecules, which is encapsulated in the interstitial spaces of photonic crystal (PC) opal film. Following the encapsulation, these molecules are selectively removed from the hydrogel network, forming an AA-MIPCH sensor. The sensor exhibits a vivid structural color that redshifts upon rebinding with different concentrations of AA molecules. This alteration in structural coloration serves as a straightforward and visually discernible indicator of the sensor response and enables the quantitative measurement of the target molecule. The sensor exhibits remarkable sensitivity, featuring a low limit of detection (LoD) of 0.011 µM with high selectivity, minimal response time, and promising long-term stability. In addition, the sensor demonstrates its capability to detect the AA even from the complex matrix. A CNN-based deep learning algorithm in MATLAB® was employed to quantitatively predict the concentration of the target molecule. The integration with the machine learning algorithm yields a highly efficient and accurate smart sensor system that is well-suited for real-time sensing of ascorbic acid. [ABSTRACT FROM AUTHOR]

• Introduce a novel fabrication method to design optical cavity with SU-8 photoresist. • The optical cavity can localize wave around 1269.3 nm, and the Q factor in the cavity is comparatively higher. • The smaller thickness of SU-8, the higher quality factor Q value can be obtained. • Experiment showed that a high quality factor of Q = 8200 could be obtained. How to control electromagnetic wave effectively is the key to the realization of applicable filters in many optics technologies. In our work, a SU-8 photoresist micro-disk is written onto a photonic crystal waveguide to control electromagnetic wave. Corresponding simulation and experiment shows that, the quality Q increases as the thickness of SU-8 smaller. When the thickness exceeds 400 nm, the change of thickness has little influence on electromagnetic waves. Besides, the increase of the radius of disc-shaped SU-8 can also increase the Q value. By optimizing the simulation and experimental data, we can successfully create a SU-8 photoresist micro-disk cavity with the thickness of 5 µm and height of 20 nm, the quality factor of Q can reach 8200. However, longer exposure time and more stable experimental equipment is needed if we want to get a larger radius. The method in our work by using SU-8 photoresist micro-disk on photonic crystals to control electromagnetic wave is more practical and flexible, which can provide new significance for research into optical filter. [ABSTRACT FROM AUTHOR]

In this paper, the implementation of an all-optical full adder based on a two-dimensional photonic crystal is proposed. The proposed structure consists of hexagonal lattice of silicon rods embedded in air substrate. To design the proposed optical full adder, three nonlinear ring resonators, some linear waveguides, and some point defects are used. The switching mechanism of the ring resonators is based on nonlinear Kerr effect. The performance of the proposed structure has been analyzed and investigated by using plane wave expansion (PWE) and finite difference time domain (FDTD) methods. The minimum contrast ratio of the structure is 17.02 dB. The response time of the structure is 0.724 ps and can operate at a bit rate of 1.381 Tb/s. The proposed structure is simple, compact, and offers high contrast ratio, fast response time along with high bit rate and therefore can be a promising candidate for high speed data processing, computing, networking, and optical integrated circuits. • In this paper, we have proposed an all-optical full adder using a 2D hexagonal Si-air photonic crystal. • The proposed optical full adder has been designed by using three nonlinear ring resonators along with some linear waveguides. • The switching functionalities of the ring resonators have been achieved by utilizing nonlinear Kerr effect. • The proposed structure is simple, compact, offers high contrast ratio, fast response time and high bit rate respectively. [ABSTRACT FROM AUTHOR]

Semitransparent photovoltaics (STPV) provide a promise solution for building integrated photovoltaic glazing and automotive applications. However, current methods to achieve transparency make it difficult for STPV to simultaneously have high light-utilization efficiency and neutral color. Here, we propose a selective polarization transmission approach to achieve transparency of PV by utilizing the polarization-selective property of photonic crystals. And, a multiscale multiphysics theoretical model is developed for accurate analyses of optical, electrical, and thermal performance (average visible transmission AVT, photoelectrical conversion efficiency PCE, light-utilization efficiency LUE and U-value) of the grating photonic crystal (G-PC)-based PV glazing. Based on the polarization-selective property of G-PC, the G-PC based PV glazing can offer PCEs of 19.30%, 14.81%, and 11.75% at the AVTs of 25.10%, 40.11%, and 50.28%, respectively. Moreover, the transmitted light can maintain a neutral color within the variation of the incidence angle from 0 to 60 ̊. The U-value of double-layer G-PC based PV glazing is 3.43 W/m2/K at the ambient temperature of −20 °C, and it can be reduced to 1.21 W/m2/K when air layer thickness increase from 460 nm to 10 mm. Furthermore, based the analyses under real-world conditions, it can be found that the G-PC based PV glazing can offer relatively stable performance over the effective time period. • A selective polarization transmission approach to achieve transparency of PV • A novel grating photonic crystal (G-PC)-based PV glazing • G-PC based PV glazing with high LUE and neutral color • Multiscale optical, photovoltaic, thermal coupled theoretical model • Stable performance of G-PC based PV glazing under real-world conditions [ABSTRACT FROM AUTHOR]

• A low temperature sensor is designed using 1-dimensional photonic crystal. • Dielectric-superconductor layer is used as 1D photonic crystal sensor. • Fabrication complexity is reduced by using single substrate (superconductor) • For the first time, a very high sensitivity of 1.524 nm/K is achieved. 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 YaBa 2 Cu 3 O 7. 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 of single superconductor material 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. [ABSTRACT FROM AUTHOR]

• Pressure-stored thermochromic photonic crystal (PSTPC) with compressed non-close-packing structures has been fabricated. • The PSTPC exhibits a unique working mechanism of heating-induced lattice expansion and color redshift by releasing pressure. • PSTPCs display emerging applications, including hot warning labels, ink-free rewritable papers, and anti-counterfeiting tags. Conventional thermochromic photonic crystal (TPC) hydrogels and liquids have gained prominence due to their unique capability of adjusting their colors by temperature (T). However, challenges including non-recordable structural colors, poor stability, and limited color tunability significantly limit their advanced applications. To address these issues, a versatile pressure-stored TPC (PSTPC) with repeatable fixable compressed non-close-packing structures has been fabricated based on combining phase-changing materials and elastic photonic crystals. Distinguishing from conventional TPCs, PSTPCs possess 1) recordable colors with excellent stability under normal conditions; 2) adjustable colors from red to blue by simply altering storable pressure; and 3) a T-triggered color change by releasing the pressure. These PSTPCs have been experimentally proved to be ideal candidates for various applications, including hot warning labels, ink-free rewritable papers, and elaborate anti-counterfeiting tags. This work offers a new perspective for designing and fabricating combined materials-based stimulus-responsive structural color materials with advanced multifunctional applications. [ABSTRACT FROM AUTHOR]

Solar energy is widespread and easily accessible which make it the most promising renewable energy to solve energy crisis. As the ubiquitous distribution of selective solar absorbers (SSAs) employed in architecture and street, their substantially contributions to mitigate environment pollution and facilitate daily energy consumption are important; however, its implementation has been largely limited to poor color display and unideal cost-efficiency. Here, we develop a bio-inspired selective solar absorber (Bio-SSA) for use as an aesthetic compatible photothermal convector based on SiO 2 /W/SiO 2 /Cu resonant absorption cavity and two-dimension photonic crystal (PC), in which the solar absorption and infrared (IR) emissivity are 81.1 % and 0.17 with 7 different color display all in one. The calculated theoretically saving of year-round electricity energy up to maximum 1598 KWh when implemented in high altitude regions in China. Such Bio-SSA enjoys low-cost and simple configuration can further been utilized in large-scale and path a new way for architecture integratable solar energy system. • Compatible with the selective solar absorption of high-efficiency solar absorption and low IR emissivity. • Realizing for the first time the full-color presentation on a single device through light diffraction and scattering. • Holding great potential for integrating with architectural designs due to feasible and fast fabrication. [ABSTRACT FROM AUTHOR]

This study explores novel approaches to enhance photocatalysis efficiency by introducing a photonic crystal (PC)-enhanced, multi-layered sub-bandgap photocatalytic reactor. The design aims to effectively utilize sub-bandgap photons that might otherwise go unused. The device consists of three types of layers: (1) two polymeric triplet-triplet annihilation upconversion (TTA-UC) layers converting low-energy green photons (λ Ex = 532 nm, 2.33 eV) to high-energy blue photons (λ Em = 425 nm, 2.92 eV), (2) a platinum-decorated WO 3 layer (E g = 2.8 eV) serving as a visible-light photocatalyst, and (3) a PC layer optimizing both TTA-UC and photocatalysis. The integration of the PC layer resulted in a 1.9-fold increase in UC emission and a 7.9-fold enhancement in hydroxyl radical (•OH) generation, achieved under low-intensity sub-bandgap irradiation (17.6 mW cm–2). Consequently, the combined layered structure of TTA/Pt-WO 3 /TTA/PC achieved a remarkable 38.8-fold improvement in •OH production, leading to outstanding degradation capability for various organic pollutants (e.g., 4-chlorophenol, bisphenol A, and methylene blue). This multi-layered sub-bandgap photocatalytic structure, which uniquely combines TTA-UC and PC layers, offers valuable insights into designing efficient photocatalytic systems for future solar-driven environmental remediation. [Display omitted] • Facile PC fabrication enhances TTA-UC optical properties. • PC improves both TTA-UC emission and photocatalytic •OH generation. • TTA/Pt-WO 3 /TTA/PC multi-layered system effectively decomposes Pollutants. [ABSTRACT FROM AUTHOR]

The development of sensitive and efficient analytical methods for multiple biomarkers is crucial for cancer screening at early stage. MicroRNAs (miRNAs) are a kind of biomarkers with diagnostic potential for cancer. However, the ultrasensitive and logical analysis of multiple miRNAs with simple operation still faces some challenges. Herein, a photonic crystal (PC)-enhanced fluorescence biosensor with logic gate operation based on one-pot cascade amplification DNA circuit was developed for enzyme-free and ultrasensitive analysis of two cancer-related miRNAs. The fluorescence biosensor was performed by biochemical recognition amplification module (BCRAM) and physical enhancement module (PEM) to achieve logical and sensitive detection. In the BCRAM, one-pot cascade amplification circuit consisted of the upstream parallel entropy-driven circuit (EDC) and the downstream shared catalytic hairpin assembly (CHA). The input of target miRNA would trigger each corresponding EDC, and the parallel EDCs released the same R strand for triggering subsequent CHA; thus, the OR logic gate was obtained with minimization of design and operation. In the PEM, photonic crystal (PC) array was prepared easily for specifically enhancing the fluorescence output from BCRAM by the optical modulation capabilities; meanwhile, the high-throughput signal readout was achieved by microplate analyzer. Benefiting from the integrated advantages of two modules, the proposed biosensor achieved ultrasensitive detection of two miRNAs with easy logic gate operation, obtaining the LODs of 8.6 fM and 6.7 fM under isothermal and enzyme-free conditions. Hence, the biosensor has the advantages of high sensitivity, easy operation, multiplex and high-throughput analysis, showing great potential for cancer screening at early stage. [Display omitted] • An ultrasensitive fluorescence biosensor integrated cascade DNA circuit and PC. • OR logic gate with minimized design and operation was used for two-miRNA analysis. • The whole cascade DNA circuit was one-pot, enzyme-free and isothermal. • High-throughput signal readout was achieved with PC array and microplate analyzer. [ABSTRACT FROM AUTHOR]

• Narrowband metalens enable high-definition projection and imaging in portable devices. • A high integration design scheme that combines filtering and focusing into one. • The proposed narrowband metalens is almost unaffected by negative dispersion. • The numerical value of the modulation transfer function at the receiving end is almost unaffected by angular variations. • The light spot matrix at the projection end is almost unaffected within the operating bandwidth. In recent years, three-dimensional (3D) optical imaging has played a significant role in rapid 3D modeling fields, including applications such as cellphone camera-assisted 3D imaging and facial recognition. However, commonly used portable near-infrared vertical-cavity surface-emitting lasers (VCSELs) often have a wide wavelength bandwidth, which makes it challenging to mitigate the effects of dispersion on high numerical aperture metalenses. This can result in a sudden drop in optical performance. Here, we proposed the utilization of multi-layer coating to construct a one-dimensional photonic crystal (1D PhC) cavity, which provide a narrow working wavelength band. A narrowband focusing is achieved by cascading an all-dielectric metalens at the end of the 1D PhC crystal. The proposed narrowband metalens exhibits a 1.6-nm bandwidth at a 1540-nm telecom band, and which was nearly 12 times smaller when compared to normal portable flat lasers. In addition, the operational wavelength position can be tuned by adjusting the scale of the 1D PhC cavity within the wavelength range of 800–1700 nm. Furthermore, narrowband metalenses significantly outperform normal metalenses for a 4 × 4 array light source array focusing dot projection with 100-degree field of angle. We proposed this device to enhance the performance of portable VCSEL-integrated metalenses, which holds great potential for the future of portable high-definition 3D imaging and display. A 940-nm VCSEL is a standard light source for dot projections in 3D imaging reconstruction. The detailed information of the metalenses design for a 940-nm VCSEL is also investigated and reported. [ABSTRACT FROM AUTHOR]

Dual network agar/P(NIPAm-Am) photonic crystal hydrogel offers a unique combination of structural color, mechanochromic behavior, water retention and solvent identification is presented. [Display omitted] • Dual-network agar/P(NIPAm-Am) photonic crystal hydrogel with mechanochromic property is successfully synthesized. • The photonic crystal hydrogel exhibits excellent water retention capacity for up to 15 days with maintained structural color. • The photonic crystal hydrogel exhibits multi-responsive properties induced by external environmental stimuli. Photonic crystal hydrogels are obtained by assembling Fe 3 O 4 @C nanoparticles within the agar/P(N-isopropylacrylamide-acrylamide) (agar/P(NIPAm-Am)) dual-networks. The dual-network photonic crystal hydrogel offers a combination of structural color, mechanochromic behavior, water retention, solvent identification features, making it an exciting prospect for applications such as chromogenic display and sensing. [ABSTRACT FROM AUTHOR]

A dual-color ratiometric fluorescence sensor based on photonic crystals (PCs) was developed to detect tetracycline (TC) in food. PC was fabricated via self-assembly of carbon dots (CDs)–loaded SiO 2 nanoparticles. Gold nanoclusters (AuNCs) and copper ions (Cu2+) were then adsorbed onto the PC for sensor fabrication. The fluorescence of AuNCs was amplified by the PC with an enhancement ratio of 7.6, providing higher sensitivity. The fluorescence of AuNCs was quenched by Cu2+, whereas that of CDs remained unchanged as an internal reference. TC restored the fluorescence of AuNCs owing to its complexation with Cu2+, resulting in a change in the fluorescence intensity ratio. The sensor exhibited a good linear relationship with TC concentrations ranging from 0.1 to 10 μM, with a detection limit of 34 nM. Furthermore, the sensor was applied for TC detection in food with satisfactory recoveries and relative standard deviations, revealing great potential in practical application. • A ratiometric fluorescence sensor based on photonic crystal was fabricated. • The fluorescence of Au nanoclusters was enhanced with an enhancement ratio of 7.6. • The sensor exhibited high sensitive for tetracycline with detection limit of 34 nM. • The method provides an original approach for the design of fluorescence sensor. [ABSTRACT FROM AUTHOR]

The development of terahertz (THz) waveguides is limited by the high-conductivity losses of metals, the surface roughness, and the high-absorption of the dielectric materials. Consequently, dry air is certainly the most favorable medium to propagate THz radiations. A novel hollow-core THz waveguide enabling efficient THz wave propagation over 72 cm long length, is presented in this study. THz waves guiding in a hollow-core is achieved by an out-of-plane Photonic Band Gap (PBG) crystal cladding with a design inspired from the technology of hollow core PBG-crystal fibers. These fibers developed in the optical domains have demonstrated exceptional performances such as single mode propagation of light with low attenuation on kilometer length scales. The properties of the PBG guiding mechanism to forbid THz waves extension in the crystal cladding is exploited for enabling low-loss propagation in a waveguide fabricated with a highly absorptive material (ex. silica). PBG guidance into this new class of hollow-core THz waveguide were demonstrated theoretically and experimentally. • A novel hollow-core THz waveguide design inspired from the Photonic BandGap fibers is proposed. • PBG guiding within a hollow-core THz waveguide are theoretically and experimentally demonstrated. • These THz waveguides composed of an array of silica rods allow the use of highly absorptive materials. • Low-loss propagation (0.5 dB/m), three orders of magnitude lower than the coefficient absorption of silica is reported. • Efficient THz waves propagation is experimentally demonstrated within 72-cm long waveguides. [ABSTRACT FROM AUTHOR]

The prompt identification of organic solvents is essential in many practical scenarios. This work introduces a compact optical device for rapid, non-contact detection of organic solvents. The fabrication of the GaN chip employs a monolithic integration approach, enabling the simultaneous formation of on-chip components responsible for light emission and light detection. The self-assembled polystyrene (PS) spheres embedded in a polydimethylsiloxane (PDMS) layer as photonic crystals can effectively induce distinct optical changes when exposed to organic solvents. By analyzing the magnitude and recovery time of the photocurrent signals, up to seven types of organic samples can be distinguished. Different from traditional optical sensing systems, the proposed chip-level integration strategy eliminates the need for external assembly of optical components, resulting in an ultracompact millimeter-sized sensing unit. The developed device also offers features of simplicity of use and a short measurement time of less than 10 s, making it a feasible solution for quick detection in emergency scenarios. [Display omitted] ● A GaN chip with PDMS/PS photonic crystal has been demonstrated for rapid, non-contact identification of organic solvents. ● The compact, cost-effective sensing device operates easily without external optical components. ● The fabrication process is highly scalable, simplifying integration and reducing packaging costs. ● The sensing device can detect up to seven organic samples, with a short measurement time of less than 10 seconds. [ABSTRACT FROM AUTHOR]

Cellulose nanocrystals (CNCs), acrylamide (AAm) and poly (ethylene glycol) (PEG) can be co-assembled and photopolymerized into responsive, patterned photonic films with chiral nematic (N*) structures. Here, we report stimuli-responsive CNC/AAm/ PEG composite films (CFs) for use in humidity sensing. With the increase of AAm content, the CFs had an increased helical pitch and showed a red shift. With the adding of PEG, the CFs can quickly capture or release water molecules in air, which resulted in the changes of the helical pitch in N* structures and the structural color. After photopolymerization, the elastic modulus, hardness by nanomechanical testing and tensile strength of polymer films (PFs) were improved compared with CFs. The elastic modulus and hardness of PFs increased with the increase of AAm content. PFs and CFs showed different swelling properties in solutions with different EtOH / H 2 O ratio. Due to the swelling properties difference between CFs and PFs, partial photopolymerized photonic film showed photonic pattern. This research provides a new method to prepare photonic films with sensitive color response to humidity and photonic pattern, which has potential applications in the fields of sensing, anti-counterfeiting, and decoration. [Display omitted] • CNC/AAm/PEG composite film (CF) shows a red shift with increase of AAm content. • CF responses to humidity due to capturing or releasing water molecules in the air. • After photopolymerization, polymer film (PF) was cross-linked and blue-shifted. • The elastic modulus and hardness of PF are significantly enhanced. • Different swelling of CF before and after polymerization resulted in pattern. [ABSTRACT FROM AUTHOR]

A photonic crystal-based optical gas detector is proposed, incorporating phase change material (PCM) to modulate the sensing properties. The multi-gas detection process is designed in the range of 650 nm to 2500 nm. Ge 2 Sb 2 Te 5 (GST) is employed as a phase change material with significant optical property variations. It can exist in two self-sustaining, bi-stable phases: a crystalline GST (CGST) and an amorphous GST (AGST). The dielectrics (i.e. , Si, SiO 2 , GST, and Au) are used in various combinations, such as Au-Si, Au-Si-SiO 2 , Au-GST-SiO 2 , and GST-Au. Plane light waves are used to model the nanoporous structures over a broad wavelength range (650 nm to 2500 nm). The optical spectral response of the structures, including the reflectivity spectrum, power absorption spectrum, and electric field distribution, is investigated by varying the GST thickness, dimension, and geometry of the nanoholes. Liquid ammonia has the highest selectivity of any gas from 650 nm to 1000 nm, at about 29%, whereas carbon monoxide has the maximum sensitivity of 32%. The interchanging of layers increases the sensitivity of all the gases. With a sensitivity and selectivity of 78% and 40%, respectively, carbon monoxide exhibits the greatest values. [ABSTRACT FROM AUTHOR]

This study investigates the utilization of graphene micro-electromechanical systems (MEMS) and photonic crystal composite structures for spectral analysis. Results show that graphene's extreme thinness leads to significant deformation, with the photonic crystal deforming at the picometer scale. Consequently, the miniaturized spectrometer demonstrates exceptional performance, boasting dimensions on the micrometer scale, a resolution of less than 0.5 nm , and a working bandwidth exceeding 0.5 μm. Additionally, when coupled with a high-speed camera, the spectrometer enables the separation and detection of incident spectra in both the temporal and spatial domains, facilitating time and spatially resolved hyperspectral imaging. This single-detector miniaturized spectrometer is chip-integrable and holds promise for diverse applications in biology, medicine, chemical analysis, and beyond. [ABSTRACT FROM AUTHOR]

• The natural butterfly framework can function as Hybrid mode lasers. • Innovative Blue chromophores are a critical light source. • A multi-functional optical device is important for silicon photonics. Photonic crystals found within the wing of a Papilio Ulysses butterfly have demonstrated their efficacy in facilitating laser processes, particularly as a scattering material for imaging and illumination applications. This study delves into the investigation of the photonic crystal's band gap within the butterfly's wing, aiming to realize blue band-edge lasing using a newly developed gain medium comprising diphenylaminofluorene-based chromophores featuring a donor-acceptor-donor (D-A-D) motif. The versatility of the fabricated sample is highlighted, as it can function as both a single-mode laser and a random laser, with the operational mode determined by adjusting the excitation power and the direction of the pump source. Specifically, it exhibits a threshold of 2.5 μJ for random laser operation and 7.6 μJ for single-mode laser operation. The unique architectural elements found in the butterfly's wing, including the ridges on the wing scale and the photonic crystal within the scales, play distinct roles in enabling random laser and single-mode laser actions, respectively. This distinctive butterfly wing architecture holds promise for inspiring the development of future photoelectronic circuits requiring a hybrid design that incorporates both single-mode and comb-mode laser functionalities. [Display omitted] [ABSTRACT FROM AUTHOR]

Structural color is an important way to achieve the ecological coloring of textiles. SiO 2 microspheres with sizes in the range of 200–337 nm were synthesized by the Stober method and then covered with highly light-absorbing melanin PDA to form SiO 2 @PDA photonic crystals. The SiO 2 @PDA photonic crystals were assembled onto the surface of white cotton fabrics by gravity deposition to achieve structural color. The addition of polyvinylpyrrolidone (PVP) enhances interfacial bonding by forming multiple hydrogen bonds between its lactam group and the phenolic hydroxyl group of PDA, resulting in a structured color cotton fabric with high color fastness. Scanning electron microscopy (SEM) was used to study the structure and morphology of SiO 2 @PDA microspheres. The chemical compositions of PDA and PVP were surveyed by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The surface structural color of cotton fabrics was investigated by UV–Vis reflectance spectroscopy. [Display omitted] • SiO 2 @PDA microspheres to achieve structural coloring of white cotton fabrics. • Modulation of SiO 2 microsphere size can obtain a variety of structural colors. • PVP enhances color fastness of SiO 2 @PDA structured color cotton fabrics. [ABSTRACT FROM AUTHOR]

Hepatocellular carcinoma (HCC), as one of the most lethal cancers, significantly impacts human health. Attempts in this area tends to develop novel technologies with sensitive and multiplexed detection properties for early diagnosis. Here, we present novel hydrogel photonic crystal (PhC) barcodes with tyramine deposition amplified enzyme-linked immunosorbent assay (ELISA) for highly sensitive and multiplexed HCC biomarker screening. Because of the abundant amino groups of acrylic acid (AA) component, the constructed hydrogel PhC barcodes with inverse opal structure could facilitate the loading of antibody probes for subsequent detection of tumor markers. By integrating tyramine deposition amplified ELISA on the barcode, the detection signal of tumor markers has been enhanced. Based on these features, it is demonstrated that the hydrogel PhC barcodes with tyramine deposition amplified ELISA could realize highly sensitive and multiplexed detection of HCC-related biomarkers. It was found that this method is flexible, sensitive and accurate, suitable for multivariate analysis of low abundance tumor markers and future cancer diagnosis. These features make the newly developed PhC barcodes an innovation platform, which possesses tremendous potential for practical application of low abundance targets. [ABSTRACT FROM AUTHOR]

The research aims to investigate the application of photonic crystals and metal nanoparticles in the design of thin-film solar cell (TFSC). The propagation of electromagnetic waves in the vicinity of the cell and the light absorption process were simulated to analyze the performance variations of GaAs TFSC combining GaAs photonic crystals and Ti nanoparticles. By optimizing the cell model structure and doping concentration, we achieved high absorption across a broader wavelength spectrum. The research indicates that the incorporation of photonic crystals effectively extends the optical path length within the solar cell, while the integration of metal nanoparticles further enhances the cell's light absorption efficiency. Ultimately, the cell model proposed in this article achieves efficient light absorption in the wavelength range of 400–860 nm, with the absorption rates of the cell consistently exceeding 90% across all spectral bands. And nearly perfect absorption is realized in the wavelength range of 728–860 nm. Simultaneously, the performance of the cell exhibits significant improvements, culminating in a photoelectric conversion efficiency (PCE) of 34.48%. This research provides useful guidance for the development of solar cell technology and makes a positive contribution to the sustainable utilization of clean energy. We have significantly enhanced several key metrics of cell performance. • Within the wavelength range of 400–860 nm, the average absorption rate of the cell is 97.84%. • Absorption rates within the wavelength range of 728-860 nm have all exceeded 99%, achieving nearly perfect absorption. • The solar cell exhibits a short-circuit current of 34.11 mA/cm2, an open-circuit voltage of 1.132 V, a fill factor of 89.28%, and a photovoltaic efficiency of 34.48%. [ABSTRACT FROM AUTHOR]

Radiative cooling of solar cells has been proposed in recent years and has elicited much interest from fields of materials science to engineering science. Herein, a silica micro-grating photonic cooler is proposed, designed, and fabricated to radiatively cool solar cells. It is shown that the micro-grating silica can not only improve the thermal emissivity of the bulk silica to over 0.9 required for enhanced radiative cooling of solar cells but also exhibits a slight anti-reflection effect for sunlight. The outdoor experiment demonstrates that the proposed cooler can passively reduce the temperature of the commercial silicon cell by 3.6 °C when applied on the top of the cell under solar irradiance range from approximately 830 W m−2 to 990 W m−2, even though the cell already possesses a strong thermal emissivity of 0.67 and such a cooler slightly enhance the light trapping effect of the cell. This work provides an alternative way to design the solar-transparent infrared-emissive cooler for enhanced radiative cooling of solar cells and shows its cooling potential. [Display omitted] • A silica micro-grating photonic cooler is proposed to radiatively cool solar cells. • Grating silica exhibits emissivity over 0.9 and simultaneously has anti-reflection effect for sunlight. • A temperature reduction of 3.6 °C is realized for the commercial solar cell with the grating silica. [ABSTRACT FROM AUTHOR]

[Display omitted] Light trapping is a constant pursuit in photonics because of its importance in science and technology. Many mechanisms have been explored, including the use of mirrors made of materials or structures that forbid outgoing waves, and bound states in the continuum that are mirror-less but based on topology. Here we report a compound method, combining lateral mirrors and bound states in the continuum in a cooperative way, to achieve a class of on-chip optical cavities that have high quality factors and small modal volumes. Specifically, light is trapped in the transverse direction by the photonic band gap of the lateral hetero-structure and confined in the vertical direction by the constellation of multiple bound states in the continuum. As a result, unlike most bound states in the continuum found in photonic crystal slabs that are de-localized Bloch modes, we achieve light-trapping in all three dimensions and experimentally demonstrate quality factors as high as Q = 1.09 × 10 6 and modal volumes as low as V = 17.74 (λ 0 / n) 3 in the telecommunication regime. We further prove the robustness of our method through the statistical study of multiple fabricated devices. Our work provides a new method of light trapping, which can find potential applications in photonic integration, nonlinear optics and quantum computing. [ABSTRACT FROM AUTHOR]

This paper reports a flexible mechanical sensor developed by combining an opal photonic crystal and a flexible medium through UV curing technology. Under the action of external force, the deformation of the flexible medium causes the change of the photonic crystal lattice constant, which leads to the displacement of the reflection peaks, thus realizing the detection of the deformation of the film. The flexible medium is mixed by photoinitiators and polymer monomers, and its mechanical properties are directly related to the mass fraction of photoinitiators and polymer monomers. The results show that the film can reach a maximum strain of about 180% when the mass fraction of photoinitiator is 3% and the volume ratio of the polymer functional monomers is 8:2. In addition, for the responsiveness test of the sensor under tensile, the results show that at 0%, 26%, and 78% of tensile strain, its structural color is blue-shifted sequentially, and its spectral peaks are 668 nm, 535 nm, and 488 nm, respectively. Finally, the sensor is applied to the detection of acoustic waves in air, and it is found that its spectral response peaks can be obtained for acoustic waves of different frequencies (250–650 Hz), and a spectral peak at 500 Hz. This flexible photon sensor has the potential to match the acoustic resistance of water. It will greatly expand the response research of ocean exploration in the low frequency range. [Display omitted] [ABSTRACT FROM AUTHOR]

Noble metal nanostructures and photonic crystals (PhCs) have been widely investigated as substrates for constructing surface enhanced electrochemiluminescence (SE-ECL) biosensors. However, their applications are hindered by the limited enhancement intensity of surface plasmon resonance (SPR) and an incomplete mechanism for the photonic enhancement effect. Hence, developing a novel SE-ECL strategy with better signal enhanced capability and enriching our understanding of the intrinsic mechanisms for efficient bioanalysis is extremely urgent. Here, a synergistic SE-ECL strategy was developed for the sensitive determination of prostate specific antigen (PSA) protein. The randomly arranged polystyrene (r-PS) spheres and PS PhC arrays were applied to enhance the ECL emission of cadmium sulfide quantum dots (CdS QDs) and the results suggested that the PhC arrays displayed superior intensity (0.22) than the r-PS interface (0.10). Au nanoparticles (NPs) were introduced onto the two kinds of surfaces and further boosted the ECL intensity. According to the ECL measurements, Au NPs modified at the r-PS surface exhibited only a slight increase (0.13), while the PhC arrays showed approximately 5-fold enhancement (0.92), benefiting from the synergistic enhancement. The finite-difference time-domain (FDTD) simulation indicated that the ECL enhancement was ascribed to the coupled electromagnetic (EM) field at the surfaces of PS PhCs and Au NPs. The SE-ECL could achieve a detection range from 1 pg/mL to 1 μg/mL with a detection limit of 0.41 pg/mL (S/N = 3). This study provides the first combination of PhC arrays and metal surface plasmon nanostructure for the synergetic enhancement of SE-ECL systems. It opens a new avenue for the rational design of advanced ECL biosensors and shows great perspective for clinical diagnosis. Schematic illustration of the randomly arranged PS interface and the synergistically enhanced ECL biosensor. [Display omitted] • ECL performances at the PS PhCs and randomly-distributed PS spheres were discussed. • Synergetic enhancement of the QDs-based ECL with PS PhCs and Au NPs was reported. • Enhanced EM field at the surface of PS PhCs and Au NPs were simulated with FDTD. • Sensitive detection of the PSA with the synergistically enhanced ECL was realized. [ABSTRACT FROM AUTHOR]

We propose an eight-channel integrated device for electro-optic modulation and dense wavelength division multiplexing based on photonic crystals. The device consists of eight photonic crystal AAH cavities and eight reflection cavity filters to contribute a modulation module and a dense wavelength division multiplexing module, respectively. First, the physical model of the eight-channel integrated device is established, and then modeling and analyzing the transmission performance of the single channel modulator according to the coupled mode theory. The parameters of the proposed device are calculated by two dimensional finite-difference time-domain method for verification. The numerical results shows that the minimum insertion loss, channel crosstalk in the "on" state are 0.24 dB and −17.8 dB, respectively, and the extinction ratio in the "off" state is higher than 19.3 dB. The designed eight-channel integrated device has the advantages of low loss, small size (114.81 × 16 × 0.22) μ m 3 and easy cascading structure, which can realized "on" and "off" modulation with channel space of 0.8 nm, dense wavelength division multiplexing function in the operating wavelength range of 1552.8 nm–1558.4 nm and applied in data center and highly integrated optical communication system. • Most of the integrated device are use silicon nanowire waveguides, but in this paper we use photonic crystal waveguides. • The proposed integrated device can simultaneously achieve modulation and dense wavelength division multiplexing. • The eight channels integrated device is based on photonic crystals, which is flexible in design and easy to expand. [ABSTRACT FROM AUTHOR]

Two-dimensional photonic crystals (2D PhCs) select photons by cavity resonance, and can be used to design selective filters for thermophotovoltaic (TPV) applications. Due to the broad pass band and high out-band reflectance of the 2D PhC structure, the TPV system can achieve both high power density and high efficiency. However, the absorption during cavity resonance restrains the further improvement of performance. In this article, a 2D metallic PhC layer was added on top of a one-dimensional photonic crystal filter, and the best geometric parameters were obtained. The simulation indicated that the parasitic absorption of the optimized tandem photonic crystal filter can be reduced to half of the traditional metallic 2D PhC filters. The new filter also shows a sharper cut-off edge and better in-band transmittance. Moreover, an ideal thermodynamic model was applied to estimate the performance of TPV systems with a filter. Using a 1200 ∘C blackbody emitter, the spectral efficiency of the tandem photonic crystal filter can reach 73%, and the in-band transmittance is over 80%. When optimizing the filter based on existing GaSb cells, the system power conversion efficiency can reach 28%. • The filter achieves excellent out-band reflectance and high in-band transmittance. • The tandem PhC structure significantly reduces the parasitic absorption of filters. • A simplified scheme for calculating effective radiant heat transfer in TPV systems. • The efficiency of TPV system with GaSb cell can be expected to be 28% at 1473 K. [ABSTRACT FROM AUTHOR]

[Display omitted] • A wearable colorimetric sensor was developed for sweat lactate monitoring. • The device integrates sampling function and real-time sweat lactate analysis. • The wearable device was based on spherical colloidal photonic crystal hydrogel displaying low angle-dependent color variation. • This wearable, low-cost and easy-to-operate technique holds potential for point-of-care detection. The construction of reliable and sensitive wearable sensors capable of monitoring specific targets in sweat remains a challenge highly relevant to a range of sensor/diagnostic applications. Herein, we develop a wearable microfluidic platform to monitor sweat lactate, in which spherical colloidal Photonic Crystal Hydrogel (PCH) is synthesized to construct the sensing part. Thanks to the structural color of PCH, lactate concentrations can be obtained via the eye-recognizable and low angle-dependent color variation. Accurate quantitative analysis is performed on a smart phone with Matlab code by integrating the linear relationship between hue value of sample photos and lactate concentrations. The developed sweat sensor presents good selectivity and long-term stability, and it is capable of detecting lactate accurately in human sweat within the physiological range. On-body measurement performed on volunteers successfully demonstrates the applicability of the developed device. This wearable analytical platform provides a promising tool for sweat lactate detection in sports science and medical diagnosis. And it is expected to contribute to developing user-friendly wearable biochemical sensor devices. [ABSTRACT FROM AUTHOR]

In this paper, an efficient hexagonal micro-ring resonator is proposed to improve the cancer biosensor performance. The sensor is based on a two-dimensional photonic crystal lattice with a horizontal waveguide. Finite-difference time-domain method is used to calculate the response of the sensor. The simulations show that by using the optimum hexagonal micro-ring resonator, the sensor performance parameters such as full width half maximum, absorption/transmittance, quality factor & sensitivity have been improved. Various parameters are involved in the design of a micro-ring resonator, which include; the coupling area length, the side length, the inner and outer radius of the micro-ring resonator and the waveguide gap width. This study not only unveils the obscure effect of some kind of symmetries in the design of micro-ring resonators on the final device performance, but also brings important perspectives to designing micro-ring resonators for cancer sensing applications. It is found that when the length of the coupling area is equal to the width of the waveguide gap and when the lengths of the sides create the most possible symmetry in the hexagonal micro-ring resonator structure, the sensor exhibits superior performance. The best design is when the maximum possible symmetry occurs in the design of micro-ring resonators. In this research, at least 32 different hexagonal micro-ring resonators have been designed and examined from the largest to the smallest possible cases. Finally, by selecting the optimal hexagonal micro-ring resonator and using it in the proposed optical biosensor, five different types of cancer cells have been detected. Using the optimized hexagonal micro-ring resonator in the structure of optical biosensor for cancer detection has resulted in obtaining promising results in terms of quality factor, figure of merit and sensitivity with respective values of 4782, 2113 1/RIU, and 661 nm/RIU. The results obtained from the simulation of the proposed optical biosensor using the optimized micro-ring resonator show significant improvements compared to other structures in this field. • In this paper, the simulations of proposed sensor show that by using the optimum hexagonal MRR, performance have been improved. Various parameters are involved in the design of a MRR, so this study not only unveils the obscure effect of some kind of symmetries in the design of MRRs on the final device performance, but also brings important perspectives to designing MRRs for cytoplasm of cancer sensing applications. In this research, at least 32 different hexagonal MRRs have been designed and examined from the largest to the smallest possible cases. The best design is when the maximum possible symmetry occurs in the design of MRRs. By selecting the optimal hexagonal MRR and using it in the proposed optical biosensor, five different types of cytoplasm of cancer cells have been detected. The results obtained from the simulation of the proposed optical biosensor using the optimized MRR show significant improvements compared to other structures in this field. [ABSTRACT FROM AUTHOR]

Photonic crystals (PCs) are artificial structures with different dielectric constants that are arranged periodically in space and can control the propagation of electromagnetic waves of specific frequencies. The photonic bandgap can tune the photon state density, which is beneficial for the generation of random lasers (RLs). In this paper, a thin film of PMMA-doped DCJTB is spun-coated on a silicon dioxide (SiO 2)PC to produce an RL. The PC is fabricated by a convenient dip-coating method with variable PBGs by changing the diameter of SiO 2 nanospheres. By changing the position of the PBG gap, the RL emission peak can be effectively manipulated with an emission wavelength of up to 16 nm. By adding Au nanoparticles, the lasing performance is improved due to the surface plasmon resonance effect and strong photon scattering, where the emission intensity is increased by 191.9 %, and the threshold is decreased by 37.8 %. The imaging results show that the RL has low spatial coherence, which has a good application in speckle-free imaging. This study provides an effective method to produce a low threshold, high-quality RL with convenient manipulation of lasing properties, which opens the door for expanding its application in optoelectronic devices and speckle-free imaging. • Random laser is realized by spin-coating a dye-doped film on SiO 2 photonic crystals via dip-coating. • By changing the photonic bandgap, the random laser emission wavelength can be tuned by 16 nm. • By adding Au nanoparticles, the emission intensity is increased by 191.9 %, and the threshold is decreased by 37.8 %. [ABSTRACT FROM AUTHOR]

This paper introduces an innovative photonic crystal device that amalgamates a low cross-talk GaAs waveguide intersection with a ring employing phase change material (PCM) for application in all-optical neuromorphic synapses. The device uses a degenerate optical cavity housing Germanium–Antimony-Telluride (GST) phase-change material whose optical properties can be manipulated via a control signal. The proposed design facilitates the development of a non-volatile synapse for photonic neural networks and optical neuromorphic circuits. Numerical simulations using the finite difference time domain method (FDTD) exhibit a notably high-quality factor of 900 and a minimal cross-talk level of −60 dB at the intersection of two waveguides. To validate the FDTD results, the structure undergoes further simulations using the finite element method (FEM), confirming the accuracy of the initial calculations. The resultant structure achieves transmissions of 81 % and 13 % in the amorphous and fully crystalline states of PCM, respectively, enabling low output power in the crystalline state and high output power in the amorphous state. Moreover, modulation of the transmission coefficient between 13 % and 81 % is feasible by manipulating the crystallization coefficient of GST materials. To reduce the effect of the imaginary part of the refractive index of the GST material, the evaluation of the output transmission results for the GSST material (Ge 2 Sb 2 Se 4 Te 1) has been performed. The results revealed that, despite having a lower imaginary part of the refractive index compared to GST, GSST exhibits lower absorption in both amorphous and crystalline states. However, the use of GSST materials shows a 27 % reduction in the figure of merit (FOM), indicating a lower effective range and fewer degrees of freedom in the different crystallization levels of the PCM ring. To investigate the effect of fabrication defects and structural sensitivity, the radius of photonic crystal rods and the rings of GaAs and GST have been changed, and the results indicate that the radius of the photonic crystal rods and the GST ring have negligible effects on the output transmission and resonant wavelength. However, the thickness of the GaAs ring shows a high sensitivity, which leads to a change in the resonance wavelength that is utilized as an effective tool for tuning the pass wavelength through the structure within the 171 nm bandgap range. The transmission loss in the amorphous state is −0.6 dB and in the fully crystalline state −7.5 dB, which is attributed to the absorption of GST material. This proposed photonic crystal synapse structure with an area of less than 30 μm2 significantly minimizes the required space compared to similar silicon photonic structures and increases the prospects for integration and scalability. The compatibility of the materials employed with optical fibre communications at the 1310 nm wavelength further bolsters the practical feasibility of this design. In summary, this paper presents a significant advancement in the domain of neuromorphic photonics by introducing a promising structure with substantial potential for neural network synapses. • A photonic crystal device combining a waveguide intersection with a ring made of phase-change material is presented. • A non-volatile synapse suitable for integration in photonic neural networks is presented. • A notably high-quality factor of 900 and minimal cross-talk of −60 dB at the waveguide intersection is obtained. • Achieves transmittance of 70 % and 20 % in amorphous and fully crystalline states of PCM. • Occupying less than 100 μm2, the proposed synapse minimizes space requirements compared to silicon photonic structures. [ABSTRACT FROM AUTHOR]

• The design of photonic crystal waveguides with high contrast and wide bandwidth has always been a key issue in the design of photonic crystals. • However, in the past, researchers mainly focused on optimizing selected results and lacked comprehensive optimization methods for the entire parameter space. • This paper investigates the transmission characteristics of a superconducting photonic crystal waveguide with a 120° bending triangular lattice arrangement in the mid-infrared wavelength range. • Our method can increase the transmittance contrast by a factor of 5 and widen the bandwidth by a factor of 2 compared to the original values. The two-dimensional high-temperature superconducting photonic crystal structure has been widely studied as a novel type of photonic crystal structure. This paper investigates the transmission characteristics of a superconducting photonic crystal waveguide with a 120° bending triangular lattice arrangement in the mid-infrared wavelength range. Through the topology optimization methods, we have achieved enhanced transmittance contrast and widened transmission bandwidth of this waveguide. Our research provides parameter and method support for high-performance photonic crystal integrated devices. [ABSTRACT FROM AUTHOR]

Manipulating surface plasmon polariton waves for the development of micro-nano devices has been widely studied in recent years. Two-dimensional artificial photonic crystals have bandstructure characteristics like semiconductors. However, the requirement for light to be incident along the structural periodic direction poses a challenge in coupling light into the photonic crystal, thereby impeding its integrations and applications. In this work, we proposed coupling vertically incident left-circularly polarized light into a photonic crystal waveguide using a chiral plasmonic lens. Linearly-polarized light can also generate surface plasmon polariton waves and couple them into photonic crystal waveguides, but the intensity is lower. In contrast, right-circularly polarized light propagates in the opposite direction and exhibits minimal propagation into the photonic crystal waveguide. The results indicate that the proposed structure can operate broadband within the wavelength range of 620–670 nm. This method provides a simple and easily integrated coupling method for photonic crystal devices. • Light can be vertically coupled into the two-dimension photonic crystal waveguide. • The coupler has a wide operating wavelength range and can be integrated with the photonic crystal structure. • The polarization state of light after being converted by the coupler. • The research results can further show the design of a waveguide splitter. [ABSTRACT FROM AUTHOR]

[Display omitted] • A photonic crystal-based early fire warning sensor (EFWS) was fabricated. • The EFWS gives warnings for 0.9 s at 260 °C. • Color change of the EFWS is based on the chain motion of polymers. • A good candidate for non-open flame warnings in the precombustion stage. Fire detection plays a crucial role in maintaining the safety of people's lives and property. However, most early fire detectors are designed to monitor the current or voltage changes of the sensing materials, which require external power supplies. It is still a challenge to make rapid and accurate noncontact early fire detection in precombustion due to the lack of reliable alarm signals. Herein, inspired by the discoloration of chameleon skin, we developed an early fire warning sensor (EFWS) by coating photonic crystals (PCs) on a plastic sheet with thermal expansion properties. Monodispersed zinc sulfide (ZnS) was coated on the plastic sheet as abnormal detection component for EFWS. Combined with the intelligent image recognition algorithm, the EFWS was designed and gave warnings for 0.9 s at 260 °C. For the first time, a photonic crystal-based non-contact real-time monitoring EFWS in precombustion is developed. The sensing material can be directly pasted on the surface of the detected equipment, and combined with existing surveillance cameras in the detection area, early warning of fires can be achieved. The EFWS system can be used in non-open fire alarms for aircraft, buildings, electrical appliances, substations, and other places in the future. [ABSTRACT FROM AUTHOR]

A two-dimensional biosensor based on photonic crystal rods is proposed and considered. The structure is consisted of 49 × 39 arrays of Si rods in the air background. Finite-difference-time-domain (FDTD) and plane wave expansion (PWE) methods are utilized for extracting photonic band gap (PBG) and field distribution spectra. Output 1 port can be considered as a sensing medium for detection of hemoglobin concentrations in blood samples with the Quality factor (Q): (110.8 – 118.92), Sensitivity (S): 1785nm /RIU , detection limit (DL): (6.943e-4 – 7.002e-4) RIU and Figure of merit (FOM): (142.8 – 144.01) RIU −1 . Precise detection of hemoglobin concentrations can help physicians in diagnosis of anemia in early stages. Output 2 can also be utilized for diagnosis of creatinine concentrations in blood samples with the Quality factor (Q): (155 –168), Sensitivity (S): 1087nm /RIU , detection limit (DL): (8.78e-4 – 8.94e-4) RIU and Figure of merit (FOM): (112.3 – 113.9) RIU −1 . The obtained results from output 2 can help physicians in diagnosis of kidney failure diseases. As stated, the presented biosensor can be considered for early diagnosis of anemia and kidney failure and can be utilized as a considerably remarkable element in bio-optical integrated circuits. • Design of a novel biosensor based on 2-D PhCs for detection of Hemoglobin and Creatinine concentrations. • Configuring the proposed structure in the double ring shaped PhC by considering Si rods in the background of air. • Diagnosing anemia and kidney failure diseases. • For Hemoglobin, obtaining notable, Quality factor: 110.8 – 118.92 , Sensitivity: 1785nm /RIU , detection limit: 6.943e-4 – 7.002e-4 RIU , Figure of merit: 142.8 – 144.01 RIU −1 . • For Creatinine, achieving remarkable, Quality factor: 155 –168 , Sensitivity: 1087nm /RIU , detection limit: 8.78e-4 – 8.94e-4 RIU , Figure of merit: 112.3 – 113.9 RIU −1 . [ABSTRACT FROM AUTHOR]

The electromagnetic response of 3D-printed periodic carbon structures was investigated numerically and experimentally in the microwave (26–37 GHz) and terahertz (0.2–1.2 THz) frequency ranges. The reflection, transmission and absorption spectra, as well as the effects of the concentration of electromagnetic waves, were analysed and discussed. High broadband absorption was observed for the 3D-printed cellular structures based on a moderately conductive (1–30 S m−1) skeleton, whereas perfect tuneable resonant absorption could be achieved by 3D meshes made of highly conductive (1200–2000 S m−1) glassy carbon. We show that laser stereolithography (SLA) or fused deposition modelling (FDM) 3D-printing technique should be preferred for getting pre-defined required electromagnetic performances depending on the intended application. Image 1 [ABSTRACT FROM AUTHOR]

In this paper, molecular imprinting and photonic crystal techniques were combined to construct a four-channel sensor array for the simultaneous identification of various sulfonamides. The assay was composed of four units. Three of these units were prepared using sulfaguanidine, sulfamethazine, or sulfathiazole as template molecules. The fourth unit was prepared without a template molecule. The preparation was optimized to obtain maximum identification with a molar ratio of template, monomer, and cross-linker of 1:50:10. The response time was as short as 10 min. For demonstration, six sulfonamides were selected as analytes. The Bragg diffraction patterns of analytes at different concentrations were measured using the sensor array. Data obtained were analyzed using linear discrimination analysis (LDA) and principal component analysis (PCA). LDA can be applied for SAs discrimination. The message ratios of 87.6%, 94.4%, and 95.8% for six SAs at 10−4 mol L−1, 10−6 mol L−1, and 10−8 mol L−1 were achieved using LDA. The sensor array identified the mixture containing various SAs with an LDA coefficient of 86.1%, thereby indicating that the sensor array had a strong anti-interference ability. The sensor array was used to identify six SAs in fish samples. The measured data in spiked samples were consistent with the fingerprint collected from standard solutions. The accuracy rate reached 90.9%, indicating that the array can be used to identify SAs from food samples. Image 1 • Photonic crystal imprinting array was firstly reported for sulfonamide discrimination. • The applicable concentration range of sulfonamide is wide (10−4–10−8 mol/L). • The response is rapid and label-free. • The array was applicable in food analysis. [ABSTRACT FROM AUTHOR]

In this paper, the optical spectra of one-dimensional photonic crystal (PCs) are numerically investigated in UV, Visible and Infrared ranges. PCs consisting of a HTc superconducting material (YaBa 2 Cu 3 O 7) are sandwiched between dielectric layer (SiO 2 or AlN) and semiconductor layer (GaAs), where superconducting layer is considered as defects. Using transfer matrix method, all the numerical results are performed and inferred that photonic band gap shifted to higher wavelengths by increasing the temperature. It is found that when the temperature increases the PBG shifted to a long wavelength. When the defect is used in structure as dielectric or superconductor, the peak appears in PBG and his value increases as the temperature increases. [ABSTRACT FROM AUTHOR]

AIEgen- based fluorescent polymer film (DCDPP-2TPA) was placed in the middle of two different inverse opal photonic crystals, whose photonic band gaps matched with fluorescent polymer films' red region and blue region respectively. Tunable Janus luminescence and structural color depending on the viewing angle were achieved by inverse opal photonic crystals' regulation of light. [Display omitted] • AIEgen-based inverse opal Fluorescent Polymer photonic crystals Films were prepared. • Tunable Janus luminescence and structural color were achieved. • Encrypted information was decoded simply by ultraviolet light. • The prepared structure had good stability and practicability for daily use. Fluorescent polymer films (FPFs) doped with aggregation-induced emission luminogens (AIEgens) have attracted great attention of scientists for their potential to solve the aggregation-caused quenching effect of traditional fluorescent molecules. Here, to rich the information and enhance the function of FPFs, AIEgens (DCDPP-2TPA) doped FPF was placed in the middle of two different inverse opal photonic crystals (IOPCs), whose photonic band gaps matched with the FPF's red and blue region respectively. Owing to the regulation effect of the IOPCs, tunable Janus luminescence and structural color depending on the viewing angle were achieved. Through designing complex patterns in FPFs, encrypted information can be decoded simply by ultraviolet light. More importantly, the decoded information displays different luminescent colors on each side, and the luminescence on each side is tunable with viewing angles. The "sandwich" structure can be used in most daily environments. Its unique property of variable Janus emissions and structural colors endow the structure with highly safe anti-counterfeiting performance. [ABSTRACT FROM AUTHOR]

• Demodulating QAM signals only in the optical field. • Directly convert communication signals into logical signals. • Design demodulation device through nonlinear optical cavities and asymmetric optical paths. This paper proposes a novel two-dimensional photonic crystal-based 8-QAM signal demodulator with a unique combination of nonlinear cavities and line defects. It consists of chalcogenide cylinders arranged in a square lattice against an air background. The proposed structure enables 8-QAM signal demodulation in an all-optical environment. Instead of the photoelectric conversion process, the structure converts the communication signal into the corresponding optical logic signal by distinguishing the intensity and phase differences of the incident light. The performances are analyzed and calculated by using the finite difference time-domain method and the plane wave expansion method. Simulation results illustrate that the maximum response time of the demodulator is 1.067 ps, and the minimum light contrast ratio is 4.39 dB. [ABSTRACT FROM AUTHOR]