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Abstract This study explores the design, fabrication, and characterization of PTB7-based colored semi-transparent organic solar cells (ST-OSCs) with integrated MgF2/WO3 one-dimensional photonic crystals (1D-PCs). Integrating 1D-PCs enhanced light management by creating tunable photonic band gaps, leading to extraordinary color change and improved photon harvesting. For 1DPC5 − 425 the Average Visible Transmittance (AVT) values were 33.3%, and CIE x, y was 0.43, 0.52, for 1DPC3 − 650 AVT were 25.09% and CIE x, y was 0.23, 0.27, respectively. Thus, extraordinary color changes from blue to yellow could be achieved while keeping transparency. Thereupon, photovoltaic performance showed notable improvements, with Jsc increasing from 7.98 mA/cm2 to 9.95 mA/cm2 and 10.45 mA/cm2 for 1DPC5 − 425 and 1DPC3 − 650, respectively. By 1D-PC integration, power conversion efficiency (PCE) reached from 3.93 to 4.90% and 5.08% for 1DPC5 − 425 and 1DPC3 − 650, respectively. The Color Rendering Index (CRI) indicated successful color tuning and acceptable rendering, with CRI of 52 and 87. The study demonstrates that 1D-PC integration significantly enhances ST-OSCs’ optical and photovoltaic properties, paving the way for advanced energy-harvesting applications.

This study explores the design, fabrication, and characterization of PTB7-based colored semi-transparent organic solar cells (ST-OSCs) with integrated MgF2/WO3 one-dimensional photonic crystals (1D-PCs). Integrating 1D-PCs enhanced light management by creating tunable photonic band gaps, leading to extraordinary color change and improved photon harvesting. For 1DPC5 − 425 the Average Visible Transmittance (AVT) values were 33.3%, and CIE x, y was 0.43, 0.52, for 1DPC3 − 650 AVT were 25.09% and CIE x, y was 0.23, 0.27, respectively. Thus, extraordinary color changes from blue to yellow could be achieved while keeping transparency. Thereupon, photovoltaic performance showed notable improvements, with Jsc increasing from 7.98 mA/cm2 to 9.95 mA/cm2 and 10.45 mA/cm2 for 1DPC5 − 425 and 1DPC3 − 650, respectively. By 1D-PC integration, power conversion efficiency (PCE) reached from 3.93 to 4.90% and 5.08% for 1DPC5 − 425 and 1DPC3 − 650, respectively. The Color Rendering Index (CRI) indicated successful color tuning and acceptable rendering, with CRI of 52 and 87. The study demonstrates that 1D-PC integration significantly enhances ST-OSCs’ optical and photovoltaic properties, paving the way for advanced energy-harvesting applications. [ABSTRACT FROM AUTHOR]

Semitransparent organic solar cells (ST-OSCs) have garnered more interest and stand out as promising candidates for next-generation solar energy harvesters with their unique advantages. However, challenges remain for the advancement of colorful ST-OSCs, such as enhancing the light absorption and transmittance without considerable power conversion efficiency (PCE) losses. Herein, an optical analysis of silver (Ag) electrodes and one-dimensional photonic crystals (1DPCs) was conducted by simulations, revealing the presence of optical Tamm states (OTSs) at the interface of Ag/1DPCs. Furthermore, the spectral and electrical properties were fine-tuned by modulating the OTSs through theoretical simulations, utilizing PM6:Y6 as the active layer. The structural parameters of the ST-OSCs were optimized, including the Ag layer thickness, the central wavelength of 1DPCs, the first WO3 layer thickness, and the pair number of WO3/LiF. The optimization resulted in the successful development of blue, violet-blue, and red ST-OSC devices, which exhibited transmittance peak intensities ranging from 31.5% to 37.9% and PCE losses between 1.5% and 5.2%. Notably, the blue device exhibited a peak intensity of 37.0% and a PCE of 15.24%, with only a 1.5% loss in efficiency. This research presents an innovative approach to enhancing the performance of ST-OSCs, achieving a balance between high transparency and high efficiency. [ABSTRACT FROM AUTHOR]

Semitransparent organic solar cells (ST-OSCs) have garnered more interest and stand out as promising candidates for next-generation solar energy harvesters with their unique advantages. However, challenges remain for the advancement of colorful ST-OSCs, such as enhancing the light absorption and transmittance without considerable power conversion efficiency (PCE) losses. Herein, an optical analysis of silver (Ag) electrodes and one-dimensional photonic crystals (1DPCs) was conducted by simulations, revealing the presence of optical Tamm states (OTSs) at the interface of Ag/1DPCs. Furthermore, the spectral and electrical properties were fine-tuned by modulating the OTSs through theoretical simulations, utilizing PM6:Y6 as the active layer. The structural parameters of the ST-OSCs were optimized, including the Ag layer thickness, the central wavelength of 1DPCs, the first WO3 layer thickness, and the pair number of WO3/LiF. The optimization resulted in the successful development of blue, violet-blue, and red ST-OSC devices, which exhibited transmittance peak intensities ranging from 31.5% to 37.9% and PCE losses between 1.5% and 5.2%. Notably, the blue device exhibited a peak intensity of 37.0% and a PCE of 15.24%, with only a 1.5% loss in efficiency. This research presents an innovative approach to enhancing the performance of ST-OSCs, achieving a balance between high transparency and high efficiency.

This study presents the development and characterization of a disposable biochip for the detection of antibodies against the SARS-CoV-2 spike protein, a well-known target for vaccine and therapeutic development. This biochip is based on a one-dimensional photonic crystal (1DPC) deposited on a plastic substrate and designed to sustain Bloch surface waves (BSW) in the visible range. The experimental phase was carried out using the biochip in conjunction with a custom-made optical read-out platform capable of real-time refractometric detection and fluorescence-based end-point measurements. Our biochip was functionalized by immobilizing the receptor-binding domain of the spike protein onto the surface using a silanization process. Human serum samples, including a negative control and a positive sample from a recovered COVID-19 patient, were tested on the biochip. The experimental results show that the biochip discriminates between positive and negative samples in a label-free refractometric mode down to a 1:10 dilution of the sera and in quantum dot amplified refractometric and fluorescence mode down to 1:100 dilution. The results demonstrate the potential of the disposable biochip for sensitive and specific detection of COVID-19 antibodies.

In this paper, a highly sensitive 1D photonic crystal (1DPC) based biosensor is introduced and theoretically studied using the transfer matrix method, which has the capability of detecting multiple biomarkers, simultaneously. An m by n gradient refractive index (GRIN) lens array is introduced to the center of a 1DPC structure as a defect layer that is surrounded by two microfluidic channels. By irradiating a natural light source to the structure, a multiple array of the concentric rainbow appears on the output plane. The frequency range of these rainbows is highly dependent on the effective refractive index of the fluid inside the two microfluidic channels. By functionalizing the surfaces around the channels with an m by n antibody array along with the interaction of the various biomarkers, each element of the rainbow array displays the changes in the concentration of a different biomarker. Any change in the concentration of the biomarkers can cause a variation in the effective refractive index of the fluid and thus lead to a shift in the generated rainbow frequency range of the output. The size and number of the generated rainbow array may be engineered by using the central defect layer's refractive index distribution function.

In this paper, the performance of a transition metal dichalcogenides based Bloch surface wave (BSW) sensor with mono or double absentee layers is investigated. By adding mono absentee layer with high refractive index at some particular locations, the linewidth (FWHM) and the figure of merit (FOM) of the BSW sensor are improved. The BSW sensor with double absentee layers is also studied and the results indicate that FOM is further improved by using double absentee layers. In particular, the FOM of the BSW sensor with double GaAs absentee layers is up to 766.43 RIU−1, which is 5.83% higher than the one of a traditional BSW sensor without absentee layer. It is believed that the usage of absentee layers in a BSW sensor can improve its FOM, which is useful for the development of high-performance optical sensors.

We study the spectral response of a one-dimensional dielectric–metal photonic-crystal absorber. The reflection and absorption spectra in the frequency range 0.1–10 THz are obtained by applying a transfer-matrix method. The influence of different factors such as the incidence angle, the thickness and the materials of metallic and dielectric layers on the absorption spectrum of our absorber is explored. Finally, we offer a high-efficient photonic-crystal absorber based on Si–Ni with the free spectral range 1.46 THz and the finesse 2.496. The calculations reveal that high enough absorption (99.37%) and reflection (96.77%) can be achieved for our absorber. Therefore, it can be used as both a perfect absorber and a perfect reflector over a wide range of THz frequencies. [ABSTRACT FROM AUTHOR]

In this paper, we studied the transmission properties, including photonic band gap (PBG) and defect mode properties, of one-dimensional photonic crystals (1D PCs) consisting of gradient materials. When keeping the average refractive index of the gradient materials in the 1D gradient-material PCs (1D GPCs) the same as the index of the corresponding normal materials in the 1D normal-material PCs (1D NPCs), by transfer matrix method, we found that the complete 1D GPCs with high-index gradient materials benefit to achieve larger omni-PBG than that in 1D NPCs. In our high-index gradient material case, for TE(TM) wave, the optimal omni-PBGs in 1D GPCs with first- and second-order gradient materials are 38.6% (50.2%) and 15.9% (22.3%) larger than that in 1D NPCs; while for the optimal relative bandwidths of omni-PBG, the corresponding promotions are 41.1% (52.3%) and 16.1% (22.6%), respectively. In addition, when defective 1D GPCs have gradient-material defect, the position of defect modes can be adjusted by selecting proper parameters of the gradient materials. These types of research are useful for designing wide PBG devices and tunable narrow-band filters which have potential application in optical communication. [ABSTRACT FROM AUTHOR]

In the current study, we aim to limit the power dissipation in amorphous silicon solar cells by enhancing the cell absorbance at different incident angles. The current improvement is justified by adding the single-period of ternary 1D photonic crystal with texturing on the top surface, which acts as an anti-reflecting coating. The texturing shape gives the photons at least two chances to localize inside the active area of the cell. Therefore, it increases the absorbance of the cell. Moreover, we add binary one-dimensional photonic crystals with the features of a photonic band gap, which acts as a back mirror to return the photons that were transmitted inside the cell's active region. The considered structure is demonstrated by the well-defined finite element method (FEM) by using COMSOL multiphysics. [ABSTRACT FROM AUTHOR]

The significance of the optical biosensor is its ability to detect biomolecules in their natural form. Among them, photonic crystal-based biosensors analyze the refractive index changes due to molecular interaction, and that is correlated to the sample concentration instead of sample mass. In this paper, we report the sensing performance of a one-dimensional photonic crystal-based sensor for the detection of hemoglobin concentration using an asymmetric periodic structure with a single defect. We have used the transfer matrix method to analyze the reflectance properties of the photonic crystal. The resonant dip in the spectra and its shift with hemoglobin concentration is the basis of our sensor design. The proposed sensor is efficient in sensing hemoglobin concentration, the sensitivity and other sensor parameters were derived numerically, and the obtained parameters are comparable to the many of the reported values of photonic crystal-based sensors. The dependence of the defect layer thickness on the position of resonant dips and sensitivity is also demonstrated in our work. The numerical results prove that these photonic crystal biosensors are simple, cost effective and highly accurate for detecting the hemoglobin concentration. [ABSTRACT FROM AUTHOR]

The dual-channel nearly perfect absorption is realized by the coupled modes of topological interface states (TIS) in the near-infrared range. An all-dielectric layered heterostructure composed of photonic crystals (PhC)/graphene/PhC/graphene/PhC on GaAs substrate is proposed to excite the TIS at the interface of adjacent PhC with opposite topological properties. Based on finite element method (FEM) and transfer matrix method (TMM), the dual-channel absorption can be modulated by the periodic number of middle PhC, Fermi level of graphene, and angle of incident light (TE and TM polarizations). Especially, by fine-tuning the Fermi level of graphene around 0.4 eV, the absorption of both channels can be switched rapidly and synchronously. This design is hopefully integrated into silicon-based chips to control light. [ABSTRACT FROM AUTHOR]

[Display omitted] • The spectral positions of photonic bandgaps were estimated by theoretical simulation. • The first-order photonic bandgap was verified to be located in the infrared region. • The formation of the photonic bandgaps appreciably improved the overall properties. • A small amount of CuAl 2 O 4 was produced by controlling electrodeposition voltage. • The CuAl 2 O 4 formation enhanced the thermal stability of the coating properties. Solar selective absorption coatings based on anodic aluminum oxides (AAO) were prepared via an anodization technique and a subsequent alternating current electrodeposition of Cu-Ni nanoparticles at the bottom. The phase structure, microstructure and solar selective absorption properties of the AAO coatings were investigated with respect to their preparation conditions. Moreover, the dependence of the solar selective absorption properties on thermal annealing history was examined. One-dimensional AAO photonic crystal coatings were produced by anodization under period pulse voltages. The spectral positions of photonic bandgaps were estimated for the AAO photonic crystal coatings. The first-order photonic bandgap was verified to be located in the infrared region. The construction of the photonic crystal structure appreciably lowered the infrared emittance and as a result improved the overall properties of the AAO photonic crystal coatings. A small amount of CuAl 2 O 4 was formed in the electrodeposition layer of AAO photonic crystal coatings by controlling the amplitude of applied electrodeposition voltage at 14 V. The formation of the CuAl 2 O 4 minimized the oxidization of the Cu-Ni nanoparticles at elevated temperatures and thereby enhanced the thermal stability of the solar selective absorption properties. The AAO photonic crystal coating prepared under the electrodeposition voltage showed a solar absorptance of 0.90, an infrared emittance of 0.11 and a spectral selectivity of 8.12 at room temperature, while retaining a spectral selectivity of 6.47 after being annealed at 300 °C for 24 h. [ABSTRACT FROM AUTHOR]

In the current study, we aim to limit the power dissipation in amorphous silicon solar cells by enhancing the cell absorbance at different incident angles. The current improvement is justified by adding the single-period of ternary 1D photonic crystal with texturing on the top surface, which acts as an anti-reflecting coating. The texturing shape gives the photons at least two chances to localize inside the active area of the cell. Therefore, it increases the absorbance of the cell. Moreover, we add binary one-dimensional photonic crystals with the features of a photonic band gap, which acts as a back mirror to return the photons that were transmitted inside the cell’s active region. The considered structure is demonstrated by the well-defined finite element method (FEM) by using COMSOL multiphysics.

The significance of the optical biosensor is its ability to detect biomolecules in their natural form. Among them, photonic crystal-based biosensors analyze the refractive index changes due to molecular interaction, and that is correlated to the sample concentration instead of sample mass. In this paper, we report the sensing performance of a one-dimensional photonic crystal-based sensor for the detection of hemoglobin concentration using an asymmetric periodic structure with a single defect. We have used the transfer matrix method to analyze the reflectance properties of the photonic crystal. The resonant dip in the spectra and its shift with hemoglobin concentration is the basis of our sensor design. The proposed sensor is efficient in sensing hemoglobin concentration, the sensitivity and other sensor parameters were derived numerically, and the obtained parameters are comparable to the many of the reported values of photonic crystal-based sensors. The dependence of the defect layer thickness on the position of resonant dips and sensitivity is also demonstrated in our work. The numerical results prove that these photonic crystal biosensors are simple, cost effective and highly accurate for detecting the hemoglobin concentration.

In this paper, by using the transfer matrix method and introducing the plasma as the dispersion medium, we propose the tunable one-dimensional magnetized ternary plasma photonic crystal structure (APB)N, and study its omnidirectional absorption properties of TM wave in terahertz band, where A and B are two different dielectric layers, P is plasma layer, and studied the regulation of the frequency and peak of the absorption channel by the number of periods, the relative refractive index of the dielectric layer, length, density, collision frequency and magnetic field intensity of the plasma layer to the absorption channel frequency and peak value. Therefore, this paper provides an idea for the design of terahertz absorbers for omnidirectional plasma photonic crystals.

In nature, animals such as chameleons are well‐known for the complex color patterns of their skin and the ability to adapt and change the color by manipulating sophisticated photonic crystal systems. Artificial gradient photonic materials are inspired by these color patterns. A concept for the preparation of such materials and their function as tunable mechanochromic materials is presented in this work. The system consists of a 1D polymer photonic crystal on a centimeter scale on top of an elastic poly(dimethylsiloxane) substrate with a gradient in stiffness. In the unstrained state, this system reveals a uniform red reflectance over the entire sample. Upon deformation, a gradient in local strain of the substrate is formed and transferred to the photonic crystal. Depending on the magnitude of this local strain, the thickness of the photonic crystal decreases continuously, resulting in a position‐dependent blue shift of the reflectance peak and hence the color in a rainbow‐like fashion. Using more sophisticated hard‐soft‐hard‐soft‐hard gradient elastomers enables the realization of stripe‐like reflectance patterns. Thus, this approach allows for the tunable formation of reflectance gradients and complex reflectance patterns. Envisioned applications are in the field of mechanochromic sensors, telemedicine, smart materials, and metamaterials. [ABSTRACT FROM AUTHOR]

• Replacing the dielectric layers of conventional 1DPC with HMM layers achieves phase compensation to overcome the blue shift of resonant mode. • By mirror symmetry 1DPC containing HMMs and inserting defective layers to realize resonant mode with good band-edge cutoff. • The omnidirectional resonant mode position can be tuned flexibly and the proposed structure is easy to fabricate. The photonic band gap (PBG) of conventional all-dielectric one-dimension (1D) photonic crystal (PC) shifts towards the shorter wavelength (blueshift) as the incident angle increases, thus the defect mode in conventional defective all-dielectric 1DPC is also blueshifted. This leads to many limitations on the performance of the narrowband filtering. Recently, the emergence of the redshift PBG in 1DPC containing hyperbolic metamaterials (HMMs) for transverse magnetic (TM) polarization provides a possibility to achieve angle-insensitive defect mode in defective 1DPC containing HMMs. In this paper, we designed a mirror-symmetry 1DPC filter containing HMMs, and the HMM layers consist of subwavelength molybdenum disulfide/indium tin oxide (MoS 2 /ITO) multilayers, an omnidirectional defect mode at 1805.6 nm was achieved by phase compensation in mirror-symmetry 1DPC containing HMMs for the incident angle of 0˚-60˚, with a transmittance efficiency of 100 % at the vertical incidence. The position of the omnidirectional defect mode can be adjusted flexibly. This omnidirectional narrowband defect mode has important implications in the fields of sensors, detectors, and filters. [ABSTRACT FROM AUTHOR]

In the present communication, we report on the exploitation of a Bloch surface wave-enhanced fluorescence scheme for the detection of Interleukin (IL)-10 in a protein-rich buffer mimicking a biological sample. IL-10 is a cytokine known for its potent anti-inflammatory and immunosuppressive effects. It is considered a valuable biomarker for prognostic prediction for both solid tumors and hematological malignancies, and recently, a distinguishing feature of hyperinflammation during severe viral infections. To demonstrate the validity of the technique, we transferred all the reagents and working concentrations used in a gold-standard technique, such as ELISA, to our assay, with a substantial reduction in the execution time and without using any enzymatic amplification during IL-10 recognition. We estimate a limit of detection (LoD) in terms of the concentration of IL-10 in solution of the order of 110 pg/mL (5.8 pM) with a 14% accuracy; in other terms, the presented technique is compatible with the assay range and resolution (1.6 pM) of commercial gold-standard ELISA kits. Moreover, such LoD successfully matches the concentrations reported in literature for IL-10 detection in COVID-19 patients, making the BSW-based sensors a viable solution for rapid and accurate screening of COVID-19-related molecules.

The optimization process is a necessary step in the design of optimal optical devices with high performances. In this paper, optimization of unidirectional photonic crystal selective arbitrary-spaced filters based on silicon Material Si with large refractive index (n = 3.5) are achieved based on the genetic algorithm technique. The photonic crystal transmission synthesis is obtained by acting on the layer widths. Genetic algorithm is employed in order to reduce the quadratic error between the desired Gaussian function defined in advance and the synthesized power transmission spectra to obtain a desired curve and get the optimal filter layer thickness. As a result, eight filters have been synthesized around respectively the wavelengths: 1.1, 1.2, 1.3, 1.4, 1.55, 1.65, 1.75 and 1.95 μm with excellent selectivity and rejection less than 18% with a transmitted bandwidth of about 0.05 μm where a transmission of about 95% is recorded at the desired wavelengths. [ABSTRACT FROM AUTHOR]

The metal-ligand complex tris(2,2′-bipyridine)ruthenium(II) chloride (Ru probe) displays a broad emission spectrum ranging from 540 to 730 nm. The emission spectra of Ru probe were measured when placed on top of a one-dimensional photonic crystal (1DPC), which supports both Bloch surface wave (BSW) and internal modes for wavelengths below 640 nm and only internal modes above 640 nm. The S-polarized emission spectra, with the electric vector parallel to the 1DPC surface, were found to be strongly dependent on the observation angle through the coupling prism. Also, the usual single broad-emission spectrum of Ru probe on glass was converted into two or more narrow-band-spectrum on the 1DPC, with emission band maxima dependent on the observation angle. The two S-polarized emission band peaks for Ru probe were found to be consistent with coupling to the BSW and first internal mode (IM1) of the 1DPC. The same spectral shifts and changes in emission maxima were observed by using Kretschmann and reverse Kretschmann illuminations. As the coupling requires the emitter to be in proximity with the photonic structure, we calculated near- and far-field distributions of a dipole directly located on the 1DPC surface. Finite-Difference Time-Domain (FDTD) simulations were performed to confirm fluorophore coupling to the BSW and internal modes (IMs). Both the measured and simulated results showed that IM coupled emission is significant. Coupling to the IM mode occurred at longer wavelengths where the 1DPC did not support a BSW. These results demonstrate that a simple Bragg grating, without a BSW mode, can be used for detection of surface-bound fluorophores. [Display omitted] • The emission spectra of Ru probe were measured when placed on top of a 1DPC. • Coupled S-polarized emission of Ru probe on 1DPC shows 2 or more bands and their maxima shift to blue with increasing angle. • The 2 intense S-polarized Ru probe emission bands are from emission coupling to the BSW and 1st internal mode of the 1DPC. • Finite-Difference Time-Domain simulations were performed to confirm fluorophore coupling to the BSW and internal modes. • Simulated results are in excellent agreement with the experimental data. [ABSTRACT FROM AUTHOR]

Abstract The purpose of this study is to experimentally and theoretically evaluate the optical properties of a one-dimensional photonic crystal (PC) with a defect layer before and after an annealing procedure. A sputtering technique with high index (TeO x) and low index (SiO 2) materials was used to fabricate the 1D PC with a defect layer. The chemical and structural analysis of a single layer TeO x thin film was evaluated by X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), and X-Ray Diffraction (XRD). The optical constant of the single layer was also determined based on the envelope method from transmittance spectra measured by ultraviolet visible near-infrared spectrophotometry (UV-VIS-NIR). The measured reflectance spectra of the 1D PC were compared with the results simulated using the transfer matrix method (TMM) before and after the annealing procedure. A photonic bandgap (PBG) appears within the desired, near-infrared (NIR), region. The defect mode in the 1D PC was observed at λ = 1455 nm within the PBG of λ = 1235–1723 nm (Δλ = 488 nm). The reflectance spectra overall shifted toward longer wavelength due to thermal darkening effect resulting from the thermally induced optical property changes. Highlights • TeO x thin film showed thermal darkening effect after annealing procedure. • Sputtered TeO x /SiO 2 1D PC was analyzed before and after annealing procedure. • Measured reflectance spectra agreed well with the simulated results. • Reflectance spectra shifted toward longer wavelength after the annealing procedure. [ABSTRACT FROM AUTHOR]

TeO 1.4 /SiO 2 one-dimensional photonic crystals (1D PCs) were prepared using radio frequency (RF) magnetron sputtering to fabricate a reflector and a filter with photonic band gaps (PBGs) in the near infrared (NIR) region. Stoichiometry and phase state of the TeO x thin film were characterized via X-ray photoelectron spectroscopy (XPS) and X-Ray Diffraction (XRD), respectively. The microstructural and optical characteristics of the 1D PCs were evaluated using scanning electron microscopy (SEM), atomic force microscopy (AFM) and ultraviolet visible near-infrared spectrophotometer (UV-VIS-NIR). The experimental reflectance spectra were consistent with the theoretical results simulated using the transfer matrix method (TMM). For the reflector, a PBG of 1273–1676 nm (Δλ = 403 nm) was achieved in the NIR region. For the filter, the introduction of a defect layer in the 1D PC led to a resonant peak at the central wavelength of 1461 nm within the PBG of 1250–1733 nm (Δλ = 483 nm). The effects of the structural parameters, including the incident angle, the state of polarization and the thickness of the defect layer, were also theoretically analyzed. [ABSTRACT FROM AUTHOR]

We report on hybrid inorganic/organic one-dimensional photonic crystal biochips sustaining Bloch surface waves. The biochips were used, together with an optical platform operating in a label-free and fluorescence configuration simultaneously, to detect the cancer biomarker Angiopoietin 2 in a protein base buffer. The hybrid photonic crystals embed in their geometry a thin functionalization poly-acrylic acid layer deposited by plasma polymerization, which is used to immobilize a monoclonal antibody for highly specific biological recognition. The fluorescence operation mode is described in detail, putting into evidence the role of field enhancement and localization at the photonic crystal surface in the shaping and intensification of the angular fluorescence pattern. In the fluorescence operation mode, the hybrid biochips can attain the limit of detection 6 ng/ml. [ABSTRACT FROM AUTHOR]

The aim of this work is to experimentally investigate one-dimensional (1D) photonic crystals (PCs) and the photo-induced effect of their defect layer. A radio frequency (RF) magnetron sputtering technique was used to fabricate ten-pair 1D PCs with and without a single defect layer, utilizing TeO 2.33 and SiO 2 with different refractive indices. The photonic band structures in the PCs were also analyzed, and the measured transmittance (T) spectra were compared with the simulated results. The 1D PC without a defect layer had a forbidden band gap in the wavelength range of 1203–1421 nm. The 1D PC with defect layer generated a sharp peak within a photonic band gap (PBG) at the central wavelength of 1291 nm. After exposure to a He-Cd laser of λ = 325 nm, the resonant T peak shows red-shift because of photodarkening effect caused by the behavior of valence-alternation pairs (VAPs) in amorphous chalcogenides. [ABSTRACT FROM AUTHOR]

The preparation of responsive multilayered structures with quarter-wave design based on layer-by-layer deposition of sol-gel derived Nb2O5 films and spin-coated MEL type zeolite is demonstrated. The refractive indices (n) and thicknesses (d) of the layers are determined using non-linear curve fitting of the measured reflectance spectra. Besides, the surface and cross-sectional features of the multilayered structures are characterized by scanning electron microscopy (SEM). The quasi-omnidirectional photonic band for the multilayered structures is predicted theoretically, and confirmed experimentally by reflectance measurements at oblique incidence with polarized light. The sensing properties of the multilayered structures toward acetone are studied by measuring transmittance spectra prior and after vapor exposure. Furthermore, the potential of the one-dimensional photonic crystals based on the multilayered structure consisting of Nb2O5 and MEL type zeolite as a chemical sensor with optical read-out is discussed.

Fluorescence spectroscopy and imaging are now used throughout the biosciences. Fluorescence microscopes, spectrofluorometers, microwell plate readers and microarray imagers all use multiple optical components to collect, redirect and focus the emission onto single point or array imaging detectors. For almost all biological samples, except those with regular nanoscale features, emission occurs in all directions. With the exception of complex microscope objectives with large collection angles (NA ≤ 0.5), all these instruments collect only a small fraction of the total emission. Because of the increasing knowledge base on fluorophores within near-field (<200 nm) distances from plasmonic and photonic structures we can anticipate the development of compact devices in which the sample to be detected is located directly on solid state detectors such as CCDs or CMOS cameras. Near-field interactions of fluorophores with metallic or dielectric multi-layer structures (MLSs) can capture a large fraction of the total emission. Depending on the composition and dimensions of the MLSs, the spatial distribution of the sample emission results in distinct optical patterns on the detector surface. With either plain glass slides or MLSs the most commonly used front focal plane (FFP) images reveal the x-y spatial distribution of emission from the sample. Another approach, which is often used with two or three-dimensional nanostructures, is back focal plane (BFP) imaging. The BFP images reveal the angular distribution of the emission. The FFP and BFP images occur at certain distances from the sample which is determined by the details of the optical components. Obtaining these images requires multiple optical components and distances which are too large for the compact devices. For devices described in this paper, the images will be detected at a fixed distance between the sample and some arbitrary distance below the MLS which is determined by the geometry and thicknesses of the components. We refer to measurements at these locations as out-of-focal plane (OFP) imaging. Herein we describe a method to measure the optical fields at micron and multi-micron distances below the MLS, which will represent the images seen by an optically coupled array detector. The possibility of sub-surface optical images is illustrated using five different multi-layer structures. This is accomplished using an optical configuration which allows measurement at a front focal plane (FFP), back focal plane (BFP) or any OFP locations. Our OFP imaging method provides a link between the FFP images which reveals the surface distribution of fluorophores with the BFP images that reveal the angular distribution of emission. This linkage can be useful when examining structures which have nanoscale features due to fluorescence or leakage radiation from nanostructures. [ABSTRACT FROM AUTHOR]

We report on the use of an optical sensing platform based on Bloch surface waves sustained by one-dimensional photonic crystals as a novel optical tool to probe in real time the fluid flow at a boundary wall of a microfluidic channel under dynamic conditions. Understanding how fluid flow interacts with wall surfaces is crucial for a broad range of biological processes and engineering applications, such as surface wave biosensing. The proposed platform provides nanometric resolution with respect to the distance from the boundary wall sensor's surface. Here, for the first time, we report on the experimental investigation on the temporal evolution of the interface between two fluids with different refractive indices under convective and diffusive conditions. The temporal evolution of the fluids interface in proximity of the wall is recovered. From the data analysis, the diffusion coefficients of glucose and glycerol in water are measured and found in good agreement with the literature. Tuning the one-dimensional photonic crystals geometry and the Bloch surface wave's dispersion has the potential to probe the fluid flow in an extremely wide range of distances from the microfluidic channel wall. [ABSTRACT FROM AUTHOR]

To restrain the infrared radiation from high temperature objects to decrease the probability of being discovered by infrared detectors operating in the mid- and far-infrared atmospheric windows, we design a one-dimensional heterostructure photonic crystal (PC) using low-cost coating materials Te and ZnSe, and test its reflection spectra and radiant temperature. The tested results show that this PC has high average reflectance in 3- to 5-μm and 8- to 14-μm wavebands, which is 86.72% and 72.91%, respectively, and the corresponding emissivity is 0.072 and 0.194, respectively. The radiant temperatures of the PC are always lower than those of the background, with the maximal difference of the radiant temperature being 31.97°C corresponding to a background radiant temperature of 75.64°C. The study confirms that the deposited PC can effectively decrease the infrared radiation in mid- and far-infrared bands. [ABSTRACT FROM AUTHOR]

In this paper, we introduce and analytically demonstrate a novel chemical sensor based on defective 1-D photonic crystals in total internal reflection geometry, where a gradient refractive index (GRIN) defect layer is located at the end of the structure. This configuration creates an open sensing interface for real-time detection with ultrahigh sensitivity. Using the GRIN lens in the structure not only helps to tune the resonance wavelength to a desired value but also as a consequence of its special refractive index distribution function, a ring-shaped reflectance distribution appears on the output plane of the structure that plays a key role in finding the optimized refractive index of the defect layer and achieving the best resonance of the cavity modes. The resonance angle of the cavity modes is highly sensitive to the effective refractive index of the fluid flowing above the sensor. The refractive index variation of \Delta nF=10^{-8}RIU that causes \Delta \theta =3.2\times 10^-6 degrees shift at the resonance angle can be detected by this sensor. [ABSTRACT FROM PUBLISHER]

Optical biosensors based on one-dimensional photonic crystals sustaining Bloch surface waves are proposed to study antibody interactions and perform affinity studies. The presented approach utilizes two types of different antibodies anchored at the sensitive area of a photonic crystal-based biosensor. Such a strategy allows for creating two or more on-chip regions with different biochemical features as well as studying the binding kinetics of biomolecules in real time. In particular, the proposed detection system shows an estimated limit of detection for the target antibody (anti-human IgG) smaller than 0.19 nM (28 ng/mL), corresponding to a minimum surface mass coverage of 10.3 ng/cm2. Moreover, from the binding curves we successfully derived the equilibrium association and dissociation constants (KA = 7.5 × 107 M−1; KD = 13.26 nM) of the human IgG–anti-human IgG interaction.

In this article, the dual-band absorption characteristics of one-dimensional photonic crystals with graphene-based defect were theoretically analyzed and numerically simulated using the transfer matrix method. The dependence of dual-band absorption characteristics of the one-dimensional photonic crystal with graphene-based defect on period number of the structure behind the graphene layer, graphene layers, dielectric thickness of defect layer and the incident angle was obtained. Simulation results show that the absorptions with the lights whose wavelength are 699 nm and 1000 nm approximately enhance with the increasing of the layers of graphene. The absorption peaks increase with the decreasing of the dielectric thickness of defect layer and move toward the shorter wavelength. In the transverse electric (TE) mode, the absorption peaks can be regularly tuned by varying the incident angle. The results provide the theoretical basis for the study of graphene absorbers. [ABSTRACT FROM AUTHOR]

In this paper, we have studied the transmission characteristic of one-dimensional mirror structure photonic crystals (MSPCs) ( AB ) N D 1 D 2 D 3 ( BA ) N with the quantum theory method. We find there are some sharp peaks (quantum transmissivity T = 1) in the PBG of MSPCs, and the number of sharp peaks is added with the increasing of thickness, refractive index and numbers of defect layer, which is beneficial to design the optic filter of multiple channel. [ABSTRACT FROM AUTHOR]

Using finite difference time domain (FDTD) method, we numerically investigate one-dimensional photonic crystals (1D PCs) with structure, where and stand for different dielectric materials, and the graded-index (GRIN) material. The transmission properties of the multilayer structure have been studied, and the results show that a tunable narrow band-pass filter (BPF) can be obtained by changing gradient coefficients of the GRIN defect layer. For an increasing incident angle, although the transmittance becomes smaller, positions of the resonant peak remain the same, which can act as the angle-insensitive filter. [ABSTRACT FROM AUTHOR]

Abstract: In this study, we demonstrate a light harvesting method to achieve efficient semitransparent polymer solar cells (STPSCs) based on PCDTBT: PC70BM by employing one-dimensional photonic crystals (1DPCs) as reflector. The 1DPCs were constructed by N pairs of WO3/LiF, a pair means a combination of WO3 and LiF, including a layer of WO3 film and a layer of LiF film. By optimizing the number of pairs, a 1DPC with high reflectance region (400–500nm), which is exactly matched with the weak region of the (incident photon-to-electron conversion) IPCE spectrum of the reference STPSC is obtained. In contrast, the excellent STPSC with 8 pairs of 1DPC exhibited a high efficiency about 4.84% and hold an average transmittance of 25.4% in the visible range (400–700nm). [Copyright &y& Elsevier]

The preparation of responsive multilayered structures with quarter-wave design based on layer-by-layer deposition of sol-gel derived Nb2O5 films and spin-coated MEL type zeolite is demonstrated. The refractive indices (n) and thicknesses (d) of the layers are determined using non-linear curve fitting of the measured reflectance spectra. Besides, the surface and cross-sectional features of the multilayered structures are characterized by scanning electron microscopy (SEM). The quasi-omnidirectional photonic band for the multilayered structures is predicted theoretically, and confirmed experimentally by reflectance measurements at oblique incidence with polarized light. The sensing properties of the multilayered structures toward acetone are studied by measuring transmittance spectra prior and after vapor exposure. Furthermore, the potential of the one-dimensional photonic crystals based on the multilayered structure consisting of Nb2O5 and MEL type zeolite as a chemical sensor with optical read-out is discussed. [ABSTRACT FROM AUTHOR]

Phase manipulation plays a fundamental role in both optical physics and devices. It is known that the phase shift at the band edges in all-dielectric one-dimensional (1-D) photonic crystals (PCs) is near 0 or π due to the Bragg scattering mechanism. However, the band edges in all-dielectric 1-D PCs shift toward shorter wavelengths as the incident angle increases, which rules out the possibility to realize angle-insensitive (i.e., omnidirectional) phase shift. Herein, we utilize the angle-insensitive property of the band edge in a 1-D PC containing hyperbolic metamaterials to achieve angle-insensitive phase shift in the visible range. At the wavelength around the angle-insensitive band edge, the phase shift remains near zero in the incident angle range from 0 to near 90°. Our work provides a route, under the current experimental conditions, to controlling phase shift. • Angle-insensitive bandgap in 1-D photonic crystal containing hyperbolic metamaterials is designed at visible wavelengths. • Angle-insensitive phase shift is achieved at the angle-insensitive long-wavelength band edge. • As the incident angle increases from 0 to near 90°, the phase shift slightly changes from 0.036 π to −0.037 π. [ABSTRACT FROM AUTHOR]

Highlights: [•] 1D DBR overcomes the contradiction between efficiency and transparency. [•] A maximum efficiency of 4.12% with an enhancement of 24.1% is obtained. [•] The average transmittance is 55.6% in 600–800nm based on 1D DBR. [ABSTRACT FROM AUTHOR]

Abstract: There is a continuing need to increase the brightness and photostability of fluorophores for use in biotechnology, medical diagnostics, and cell imaging. One approach developed during the past decade is to use metallic surfaces and nanostructures. It is now known that excited state fluorophores display interactions with surface plasmons, which can increase the radiative decay rates, modify the spatial distribution of emission, and result in directional emission. One important example is surface plasmon-coupled emission (SPCE). In this phenomenon, the fluorophores at close distances from a thin metal film, typically silver, display emission over a small range of angles into the substrate. A disadvantage of SPCE is that the emission occurs at large angles relative to the surface normal and at angles that are larger than the critical angle for the glass substrate. The large angles make it difficult to collect all of the coupled emission and have prevented the use of SPCE with high-throughput and/or array applications. In the current article, we describe a simple multilayer metal–dielectric structure that allows excitation with light that is perpendicular (normal) to the plane and provides emission within a narrow angular distribution that is normal to the plane. This structure consists of a thin silver film on top of a multilayer dielectric Bragg grating, with no nanoscale features except for the metal or dielectric layer thicknesses. Our structure is designed to support optical Tamm states, which are trapped electromagnetic modes between the metal film and the underlying Bragg grating. We used simulations with the transfer matrix method to understand the optical properties of Tamm states and localization of the modes or electric fields in the structure. Tamm states can exist with zero in-plane wavevector components and can be created without the use of a coupling prism. We show that fluorophores on top of the metal film can interact with the Tamm state under the metal film and display Tamm state-coupled emission (TSCE). In contrast to SPCE, the Tamm states can display either S or P polarization. The TSCE angle is highly sensitive to wavelength, which suggests the use of Tamm structures to provide both directional emission and wavelength dispersion. Metallic structures can modify fluorophore decay rates but also have high losses. Photonic crystals have low losses but may lack the enhanced light-induced fields near metals. The combination of plasmonic and photonic structures offers the opportunity for radiative decay engineering to design new formats for clinical testing and other fluorescence-based applications. [Copyright &y& Elsevier]

Abstract: During the past decade the interactions of fluorophores with metallic particles and surfaces has become an active area of research. These near-field interactions of fluorophores with surface plasmons have resulted in increased brightness and directional emission. However, using metals has some disadvantages such as quenching at short fluorophore–metal distances and increased rates of energy dissipation due to lossy metals. These unfavorable effects are not expected in dielectrics. In this article, we describe the interactions of fluorophores with one-dimensional (1D) photonic crystals (PCs), which have alternating layers of dielectrics with dimensions that create a photonic band gap (PBG). Freely propagating light at the PBG wavelength will be reflected. However, similar to metals, we show that fluorophores within near-field distances of the 1DPC interacts with the structure. Our results demonstrate that these fluorophores can interact with both internal modes and Bloch surface waves (BSWs) of the 1DPC. For fluorophores on the surface of the 1DPC, the emission dominantly occurs through the 1DPC and into the substrate. We refer to these two phenomena together as Bragg grating-coupled emission (BGCE). Here we describe our preliminary results on BGCE. 1DPCs are simple to fabricate and can be handled and reused without damage. We believe that BGCE provides opportunities for new formats for fluorescence detection and sensing. [Copyright &y& Elsevier]

Abstract: One-dimensional photonic crystals (1DPCs) with the structure of (WO3/LiF) N are employed to simultaneously improve the efficiency and transmittance of low bandgap semitransparent polymer solar cells(PSCs). Within the photonic bandgap(PBG) of 580–780nm, 1DPCs with 8 pairs of WO3/LiF act as distributed reflectors (DBR), which reflects light wavelength of 580–780nm back into the PSCs for reabsorption by active layers. Power conversion efficiency (PCE) of 2.46% is obtained for the semitransparent PSCs and there is an improvement of 28.1% in the PCE when compared with that of the device without 1DPCs. Within the photonic passband of 380–580nm, the 1DPCs act as antireflection coatings. An average transmittance of 40% is remained within the wavelength range and the value is improved by 33% when compared with that of the device without the 1DPCs. Finally, it is demonstrated that the efficiency and transmittance of the device are dependent on the number of the repeated period (N). [Copyright &y& Elsevier]

We present the general formulation of light reflection using a series of one-dimensional (1D) photonic crystals (PCs) with different periods, which is made of nonabsorptive materials of any refractive indices.To have a large bandgap, the spectral range of reflection, the periods of 1D PCs must be distributed in a geometrical progression with a common ratio, r, smaller than a maximum value of rc. In this letter, the exact expressions for rc, the bandgap to mid gap ratio of the PC heterostructure and the minimum number of PCs to achieve the desired range of bandgap in single and all angles of incidence have been presented. The proposed method can be used to design the optical filters for vast range of applications such as ultraviolet (UV) filters (i.e., sunglasses, eye safety glasses, UV photography filters) and visible light filters. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2533-2536, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27123 [ABSTRACT FROM AUTHOR]

A continuous melt-process has been used to prepare multilayered polymeric films forming one-dimensional photonic crystals for which the band gap shape and position can be easily tuned to the desired design. In combination with organic fluorescent dyes, dye-doped photonic crystal distributed feed-back lasers, as well as distributed Bragg lasers formed by sandwiching a dye-doped active layer between two photonic crystal films, have been fabricated. These lasers have demonstrated low threshold and high efficiency. This fabrication method is amenable to roll-to-roll mass production at low cost and can be easily tailored to produce other multilayer-based polymeric optical and optoelectronic devices. [ABSTRACT FROM AUTHOR]

The transmission properties of a periodic structure consisting of alternating metal layers and air layers are studied by numeric methods. The metal layers are the epsilon-negative (ENG) materials. The interaction of the evanescent waves in metal layers and propagation waves in air layers forms some special transmission bands. Given proper structure parameters, one transmission frequency only allows one incident direction in the low frequency range. This structure can simultaneously achieve frequency filtering and direction filtering. [ABSTRACT FROM AUTHOR]

The spectral control is widely incorporated with the thermophotovoltaic (TPV) technology to improve the optical-electric conversion efficiency of the whole system. In order to match with GaSb photovoltaic cell, an 8-layer one-dimensional photonic crystals (PC) filter structure was designed as quarter-wave periodic structure by selecting silicon (Si) and silicon dioxide (SiO2) as candidate materials. The multilayer Si/SiO2 structure was developed for the matching filter to simultaneously realize the optimal matching with the spectral distribution of the high temperature emitter and the quantum efficiency of GaSb cell. The physical vapor deposition (PVD) method was used to fabricate the optical filter and the normal incidence optical property of the filter was measured within the spectral range from 0.7 to 3.3 μm. These experimental data were used to predict the spectral control performance in a TPV system. Finally, temperature performance experiments were carried out to establish its withstanding performance in high temperature environment. [ABSTRACT FROM AUTHOR]

This paper presents a loss reduction mechanism for coupled cavity waveguides (CCWs) relying on 1-D photonic crystals microcavities. The mechanism is based on structural modification in the vicinity of the cavity defects. With appropriate modifications, the tangential wavenumber components of the leaky guided modes, which can couple to cladding modes, can be decreased, resulting in the reduction of propagation losses due to diffraction. We numerically demonstrate the usefulness of this mechanism through the design of low loss CCWs. The diffraction losses in the CCWs, where air holes adjacent to the defects are changed in size, decrease dramatically compared with CCWs with air holes of constant size. This loss reduction mechanism can be applied even to the CCWs with an increased number of intercavity air holes, while the group velocity can be further decreased. [ABSTRACT FROM PUBLISHER]

Abstract: The propagation of light waves in one-dimensional photonic crystals (1DPCs) composed of alternating layers of two kinds of single-negative materials is investigated theoretically. The phase velocity is negative when the frequency of the light wave is smaller than the certain critical frequency , while the Poynting vector is always positive. At normal incidence, such 1DPCs may act as equivalent left-handed materials. At the inclined incidence, the effective wave vectors inside such 1DPCs do refract negatively, while the effective energy flows do not refract negatively. Therefore, at the inclined incidence, the 1DPCs are not equivalent to the left-handed materials. [Copyright &y& Elsevier]

Recent photonic device structures, including distributed Bragg reflectors (DBRs), one-dimensional (1-D) or two-dimensional (2-D) photonic crystals, and surface plasmon devices, often require nanoscale lithography techniques for their device fabrication. Focused ion beam (FIB) etching has been used as a nanolithographic tool for the creation of these nanostructures. We report the use of FIB etching as a lithographic tool that enables sub-100-nm resolution. The FIB patterning of nanoscale holes on an epitaxially grown GaAs layer is characterized. To eliminate redeposition of sputtered materials during FIB patterning, we have developed a process using a dielectric mask and subsequent dry etching. This approach creates patterns with vertical and smooth sidewalls. A thin titanium layer can be deposited on the dielectric layer to avoid surface charging effects during the FIB process. This FIB nanopatterning technique can be applied to fabricate optoelectronic devices, and we show examples of 1-D gratings in optical fibers for sensing applications, photonic crystal vertical cavity lasers, and photonic crystal defect lasers. [ABSTRACT FROM PUBLISHER]