Search

Radiation detection is being revolutionized by integrating photonic elements into scintillators. In this study, a scalable and cost‐effective method is proposed to achieve tuneable emission enhancement across the visible spectrum by colloidal self‐assembly of photonic crystals on scintillator surfaces. This concept is demonstrated for Eu3+/Tb3+‐doped Gd and Ta oxides. Widely available and affordable colloidal nanospheres of SiO2 or polymethyl methacrylate are self‐assembled on these scintillators. The size of the nanospheres is carefully optimized to match the desired emission lines of Eu3+/Tb3+. The result is homogeneous and closely‐packed structures with clear photonic bandgap in the visible range. Under X‐ray excitation, the scintillators covered with the photonic layers exhibit enhanced light extraction in the direction perpendicular to the surface, compared to isotropic emission in the bare scintillator. Such scintillation directionality, when optically matched with a proper detector, will result in higher efficiency of the overall detection system. Moreover, X‐ray imaging demonstrates an enhancement of 25% in system resolution of the scintillator supplemented with the photonic layer compared to unmodified scintillators. The proposed method is scintillator‐ and nanosphere‐agnostic, thus offering a promising versatile approach for directing the scintillation light toward a photodetector and increasing detection system performance, including high‐resolution imaging applications. [ABSTRACT FROM AUTHOR]

As one of the most stunning biological nanostructures, the single-diamond (SD) surface discovered in beetles and weevils exoskeletons possesses the widest complete photonic bandgap known to date and is renowned as the "holy grail" of photonic materials. However, the synthesis of SD is difficult due to its thermodynamical instability compared to the energetically favoured bicontinuous double diamond and other easily formed lattices; thus, the artificial fabrication of SD has long been a formidable challenge. Herein, we report a bottom-up approach to fabricate SD titania networks via a one-pot cooperative assembly scenario employing the diblock copolymer poly(ethylene oxide)-block-polystyrene as a soft template and titanium diisopropoxide bis(acetylacetonate) as an inorganic precursor in a mixed solvent, in which the SD scaffold was obtained by kinetically controlled nucleation and growth in the skeletal channels of the diamond minimal surface formed by the polymer matrix. Electron crystallography investigations revealed the formation of tetrahedrally connected SD frameworks with the space group Fd 3 m in a polycrystalline anatase form. A photonic bandgap calculation showed that the resulting SD structure has a wide and complete bandgap. This work solves the complex synthetic enigmas and offers a frontier in hyperbolic surfaces, biorelevant materials, next-generation optical devices, etc. [ABSTRACT FROM AUTHOR]

An optical photonic biosensor for the detection of microcystin (MC) has been developed using an aptamer-immobilized interpenetrating polymeric network (IPN aptamer) intertwined with solid-state cholesteric liquid crystals (CLC solid s). The IPN was constructed with a polyacrylic acid hydrogel (PAA). Aptamer immobilization enhances polarity while blocking hydrogen bonding between the carboxylic groups of PAA-IPN hydrogel, thereby increasing the swelling ratio of the PAA-IPN hydrogel. This leads to an expansion in the helical pitch of the corresponding IPN aptamer -CLC solid biosensor chip and results in a red-shift in the reflected color. Upon exposure to an aqueous MC solution, the IPN aptamer -CLC solid biosensor chip exhibits aptamer-mediated engulfment of MC, resulting in reduced polarity of the IPN aptamer complex and a consequential blue-shift in the biosensor chip color occurred. The wavelength shift of the IPN aptamer -CLC solid biosensor chip demonstrates a linear change with an increase in MC concentration from 3.8 to 150 nM, with a limit of detection of 0.88 nM. This novel optical biosensor is characterized by its low cost, simplicity, selectivity, and sensitivity, offering a promising strategy for designing similar toxin biosensors through the modification of biological receptors. [ABSTRACT FROM AUTHOR]

A one-dimensional magnetized InSb photonic crystals layered topology (PCLT) proposed in this paper can realize the functions of logic OR operation and magnetic field sensing. In the proposed PCLT, under the transverse magnetic polarization, the value and frequency of the absorption peak (AP) can be controlled by the external magnetic fields and has a high-quality factor (Q), thus OR logical operation can be achieved. Additionally, since InSb has a magneto-optical effect under magnetic fields, the parity of the structure of the PCLT which adds InSb as defect layers can be broken. Electromagnetic waves obtain nonreciprocity when propagating in opposite directions within the PCLT, which means that logical operation and magnetic field sensing based on AP can be obtained on the forward and backward scales. For the detection, on the forward scale, optimum performances of Q, sensitivity (S), the figure of merit, and detection limit are 62 372.09, 0.0169 (2 Ď€c / d) /T, 4225 Tâˆ'1, 1.2 Ă— 10âˆ'5 T, and for the backward detection, the corresponding values are 63 626.25, 0.0225 (2 Ď€c / d) /T, 5200 Tâˆ'1, 1 Ă— 10âˆ'5 T. The designed PCLT is innovative in multi-functional and multi-scale, having certain research value and prospects. [ABSTRACT FROM AUTHOR]

We propose an optical sensor based on the inverse opal (IOP) photonic structure infiltrated by a typical liquid crystalline material doped by the reactive compounds. Benefiting from the unique photonic property of the IOP structure, the composite sensor shows not only a typical textural change but also a responsive photonic band gap (PBG) upon the exposure to butylamine (BA) vapour, due to the reorientation of the liquid crystalline molecules induced by the chemical reaction between the dopant and the BA vapour. This approach simplifies the measurement process by capturing the PBG signal instead of the polarised optical texture, which does not require high cost or complex instruments and might be instructive for detecting other volatiles. [ABSTRACT FROM AUTHOR]

Holographic sensors are optical devices capable of tuning reflection wavelength, dependent upon nanostructured variations in refractive index. Computational modelling is utilized to simulate the recording and swelling characteristics of developed doubly photopolymerized (DP) holographic sensors. The holographic devices simplify fabrication processes, reduce financial costs, and improve biocompatibility. A holographic grating is achieved through in situ photopolymerization of a highly crosslinked polymer to produce nanostructured refractive index modulation. The unique swelling characteristics DP holographic sensors possess necessitate the development of system‐specific computational modelling. Hydrogel parameters, including film thickness, refractive index change, layer number, and external medium refractive index are examined for their effect on reflection spectra. Optimized computational models are utilized to study the effect of differential swelling rates of individual layer spacings on sensor response, indicating an idealized reduction in a swelling of 50% for the highly crosslinked region. A 2D photonic crystal geometry with additional periodicity is developed, to inform further sensor design opportunities. Optimized parameters for both 1D and 2D photonic structures will assist the further development of DP holographic sensors. [ABSTRACT FROM AUTHOR]

[Display omitted] A process to fabricate structures on inclined substrates has the potential to yield novel applications for colloidal-based structures. However, for conventional techniques, besides the coffee ring effect (CRE), anisotropic particle deposition along the inclination direction (IE) is expected to occur. We hypothesize that both effects can be inhibited by reducing the dispense volume during printing by direct writing. We combined an additive manufacturing technique, namely direct writing, with colloidal assembly (AMCA) for an automated and localized drop-cast of polystyrene and silica suspensions onto inclined surfaces. Herein, we investigated the influence of the substrate tilting angle and the dispense volume on the printing of colloids and the resulting structures' morphology. The results demonstrate that a reduction in the dispense volume hinders the CRE and IE for both particles' systems, even though the evaporation mode is different. For polystyrene, the droplets evaporated solely in stick-mode, enabling a "surface capturing effect", while for silica, droplets evaporated in mixed stick–slip mode and a "confinement effect" was observed, which improved uniformity of the deposition. These findings were used to generate a model of the critical droplet radius needed to print homogeneous colloidal-based structures onto inclined substrates. [ABSTRACT FROM AUTHOR]

In this work, the narrowband and broadband absorption characteristics of single layer graphene-based photonic structures are investigated. The optical features were determined utilizing the 4 × 4 transfer matrix method. The results indicate that the proposed design incorporating monolayer graphene achieves absorption rates exceeding 90% across a bandwidth of 1.8 THz. Additionally, the suggested photonic configuration has the potential to function as a triple-mode narrowband absorber through the alteration of layer positioning or the substitution of materials. The numerical relationships between the refractive indexes of materials A, B, and C have been formulated to facilitate broadband and narrowband absorption. The absorption characteristics of the proposed design have been significantly influenced by the Fermi-level of Graphene and the magnetic field. The results indicate that the absorption value of both broadband and narrowband absorbers can be dynamically adjusted by manipulating the Fermi-level of Graphene and magnetic field. The photonic configuration being proposed presents novel opportunities for the development of electrically and magnetically tunable narrowband and broadband absorbers. • The proposed design can offer both broadband and multi-mode narrowband absorption. • The triple-mode narrowband absorption with a value greater than 95% achieved. • The proposed novel design provided broadband absorption over a bandwidth of 1.8 THz. • Formulated numerical relations for broadband and multi-mode absorption. • The design enables dynamic absorption tuning via electrical and magnetic biassing. [ABSTRACT FROM AUTHOR]

We present the results of investigation of conditions leading to optimization of an optical recording medium based on photosensitive urethane–acrylate nanocomposites containing silicone oxide nanoparticles that is used for efficient recording of Bragg gratings by means of multiple-beam interference. It is demonstrated that the choice of most efficient monomers and their concentration in the nanocomposite depending on their structure and the rate of polymerization, followed by finding optimal intensity of recording radiation for given composition, allows regulating the conditions for component diffusion thereby optimizing their redistribution in the recording medium and formation of regions with different values of refractive index. The results of the study can be used for creation of complex 2D and 3D photonic structures based on purposeful modification of light-sensitive polymer nanocomposites exhibiting various properties (luminescent, nonlinear-optical, etc.) [ABSTRACT FROM AUTHOR]

Anodizing of valve metals under oscillating conditions is one of versatile and reproducible methods of the preparation of one-dimensional photonic crystals. Here, an effect of anodizing voltage profile on morphology and optical properties of anodic titanium oxide photonic crystals is investigated. Samples are obtained by cyclic anodizing of titanium in ethylene glycol based electrolyte using sine, triangle, and square wave voltage versus charge density modulation. The optimization of anodizing parameters allowed us to prepare anodic titanium oxide photonic crystals with reflectance within the photonic band gap of up to 85%. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Cost reduction and enhanced cooling performance are strongly demanded for daytime passive radiative cooling due to its attractive cooling strategy that does not require any energy input. Its potential application varies widely from air conditioning systems for buildings, photovoltaic cells, electronic device cooling and automobiles. However, recently proposed daytime passive radiative coolers are based on photonic structures which are high in cost. A relatively cheap metal oxide material, TiO 2 , which lowers the cost but is highly emissive in the mid-infrared range has been used, also improving the cooling performance of the photonic daytime passive radiative cooler. An optimized TiO 2 –SiO 2 alternating multi-layered photonic daytime radiative cooler with average emissivity of 0.84 within 8–13 μm while reflecting 94% of incident solar energy is developed. Its net cooling power is estimated to be 136.3 W/m2 at ambient air temperature of 27 °C which shows an improvement of 90 W/m2 compared to that of the HfO 2 -SiO 2 photonic radiative cooler. Last, a field test has been conducted in Hong Kong's subtropical climate (i.e. relative humidity = 60–70%) to investigate its feasibility, and with the help of solar shading, successfully demonstrated temperature reduction of 7.2 °C with a net cooling power of 14.3 W/m2 under direct sunlight. • An optimized TiO 2 –SiO 2 radiative cooler showed the emissivity (8–13 μm) of 0.84. • The radiative cooler was measured to absorb 58.5 W/m2 of solar irradiance. • The net cooling power of the radiative cooler was estimated to be 136.6 W/m2. • In Hong Kong's sub-tropical climate, the cooler remained 7.2 °C below the ambient. • The radiative cooler generated a net cooling power of 14.3 W/m2 during the daytime. [ABSTRACT FROM AUTHOR]

[Display omitted] • A confined assembly strategy is reported for polarized structural coloration. • DCP is adjusted by kinetic trapping multi-domain cholesteric mesophases. • The chiral photonic materials can be applied for information storage and encryption. Chiroptical materials with tunable circular polarization performances have gained wide interest because of promising applications in optical devices and information communication. However, limited by their intrinsic chirality, such materials suffer from serious deficiencies in dynamical manipulation on circularly polarized light (CPL). Here, we demonstrate a kinetic trapping approach to capture multi-domain cholesteric mesophases for polarization-dependent structural coloration. The resultant photonic structures depicted by limited solvent evaporation display light control from selective left-handed circularly polarized light reflection to dual reflection, as a result of forming highly tilted and distorted domains with a phase-retardation effect. Notably, a positive linear correlation is established between the circular polarization behavior and structural orientation regulated by the solvent evaporation. The tunable circular polarization structural colors enable the application of the photonic materials for complex encryption in terms of polychromatic coding arrays. The confined-anisotropic-fabrication method of photonic structures paves a foundation toward advanced functional materials with promising applications in light science and technology. [ABSTRACT FROM AUTHOR]

In this work, the design and the performance of a two dimensional photonic structure with hexagonal geometry is numerically investigated by plane wave expansion (PWE) method. The structure consists in a zinc oxide (ZnO) substrate patterned in a hexagonal configuration with periodic holes with different radius. The photonic crystals exhibited band gaps in the near infrared wavelength range. This kind of photonic structures can be used for a wide range of optoelectronic applications. [ABSTRACT FROM AUTHOR]

The evolution of the characteristics of one-dimensional phase diffraction structures during their optical induction by Bessel-like monochromatic beams in photorefractive samples of lithium niobate is studied experimentally. Both, one-dimensional (1D) and two-dimensional (2D) Bessel-like beams with different topology of 2D beam cross-sections are formed from Gaussian laser beams using the amplitude masks with rectangular and annular apertures. These almost diffraction-free light fields with wavelengths of 457 and 532 nm can change the refractive indices of photorefractive lithium niobate samples and form within them the nonlinear photonic diffraction structures. [ABSTRACT FROM AUTHOR]

Abstract RE 2 O 2 S:Yb3+ and RE 2 O 2 S:Yb3+,Ti,Mg2+ near-infrared persistent luminescence materials (RE3+: La, Gd, Y) were designed based on the efficient red-emitting RE 2 O 2 S:Eu3+,Ti,Mg2+, due to the similar ground state level positions between Eu3+ and Yb3+. The Y 2 O 2 S:Yb3+,Ti,Mg2+ showed the longest near-infrared (~983 nm) persistent luminescence time (~1 h) when excited at the charge transfer transition, demonstrating that Ti,Mg2+ co-doping enhances the persistent luminescence only for the Y 2 O 2 S host. The unprecedented relationship between Eu3+ and Yb3+ persistent luminescence opens a new path in the systematic design of efficient Yb3+-activated persistent luminescence materials e.g. Y 2 O 2 S:Yb3+,Ti,Mg2+, which present potential for photonic applications such as bioimaging probes. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract Nanocomposites based on urethane-acrylate monomers stabilized at high concentration of silica nanoparticles were fabricated and investigated with the aim to produce efficient volume Bragg grating elements. Their sensitivity in the green spectral region and high modulation depth of the refractive index in the optically recorded elements are determined by the redistribution of combined monomers and silica nanoparticles, by the property of initiators of polymerization as well as by the parameters of recording process. The developed materials and methods can be used for creation of versatile photonic elements, for manipulation of optical wavefronts or beam propagation, for optical sensing. Highlights • Light sensitive nanocomposites based on urethane-acrylate monomers were developed. • Sensitivity to green lasers, high modulation of the refractive index was realized. • Correlations between the composition, recording processes and parameters of gratings were established. • 1D, 2D, 3D holographic elements were recorded. [ABSTRACT FROM AUTHOR]

The potential of radiative cooling (RC) technology to passively and sustainably harvest cold energy has received a lot of interest. Since RC surface is installed outdoors for the long term and operates under time-varying environmental conditions, photonic structures constructing the RC surface need to be carefully designed based on proper theoretical modeling. However, a theoretical model for accumulated cooling performance that reflects environmental factors was scarcely developed for photonic structure design. This paper presents a more practical approach for estimating RC performance as an accumulated cold energy production (ACEP). ACEP stands for the time integration of cooling power, which is modeled to comprehensively account for a wide range of time-dependent environmental factors, including mostly neglected cloud coverage as well. The realistic performance of an RC surface at any location on Earth can be estimated without conducting any experiments. Utilizing the benefits of ACEP, photonic structures are separately optimized for 15 different locations with different climates. As a result, the universal optimum for all climates achieves 2 to 4 percent greater ACEP than the conventionally driven optimum. Based on the optimized results, we have developed a strategy for selecting radiative cooling structures based on regional climate conditions utilizing ACEP as a guiding metric. Furthermore, the impact of each environmental factor on RC performance is investigated by analyzing the ACEP components. • Realistic model for climate-dependent radiative cooling performance is introduced. • Representative radiative cooling structures are optimized for each climatic region. • A single 4-layered optimum demonstrates robust operation across diverse climates. • We have developed a cooling structure selection strategy for specific climates. • We comprehensively analyze the impact of climatic factors on cooling performance. [ABSTRACT FROM AUTHOR]

Device modeling of CH 3 NH 3 PbI 3 based controllable photonic structure and plasmonic nanoparticles perovskite solar cells (PSC) was performed. In recent years, light trapping (LT) and plasmonic structures in PSCs have been developed and attracted widespread attention and encouraged researchers to develop and test many architectures in this area. Also, using controllable photonic structures and plasmonic nanoparticles in PSCs significantly affect the power conversion efficiency (PCE). LT by photonic structure and also the interaction of incident light with plasmonic nanoparticles (NPs) is considered as a hopeful way to enhance the PCE of PSCs in this simulation. For accurate calculation and also considering all parameters on PSC, the present simulation is done using the finite element method (FEM). The simulation results showed that using a photonic structure significantly affects the photovoltaic result of the PSC, and the PCE reached from 15.62 % for the planar structure to 16.17 % for the photonic structure. Here, we concentrate on a significant aspect of nanostructures that minimizes light loss by optimizing and managing light to achieve high PCE for the PSC. Then we used plasmonic NPs at the top of the electron layer transfer (ETL), active layer, and hole transfer layer (HTL), and the best position to achieve the highest PCE was the top of HTL. Moreover, an additional layer as a complimentary layer (CH 3 NH 3 SnI 3) was used to maximize efficiency with values of short circuit current (J sc) 27.81 (mA/cm2), open circuit voltage (V oc) 0.949 (V), fill factor (FF) 81.77 % and PCE 21.85 %. Using these combined techniques opens horizons of improvement for the PCE of PSC. [Display omitted] • Light absorption increase using plasmonic nanoparticles (PNPs) was investigated. • Using the light trap (LT) mechanism increases active layer absorption over planar structure. • Performance of the proposed PSC is highly dependent on the position and location of PNPs. • Placing Au PNPs in the double active layer increased PCE to 21.85 %. [ABSTRACT FROM AUTHOR]

Optical filter based locking system using photonic structure is explored in this research. Here, photonic structure is envisaged by the apt periodic combination of silicon and air. The proposed photonic structure interface with hardware implementation to realize the optical fiber based locking system. This paper emphasizes on both simulation outcomes which is investigated through reflectance characteristics and hardware implementation using Arduino board to display the lock/ unlock status. Finally, this work divulges that different type of locking system may be designed with varying the input parameters of photonic structures. [ABSTRACT FROM AUTHOR]

Photonic nanostructures are now widely investigated as light trapping textures to achieve significant absorption in thin film solar cells. In this paper, we quickly designed a high efficiency photonic structure for thin film silicon solar cells. Based on the coupled mode theory, we compared classic lattice photonic structures and demonstrated triangular lattice structure exhibits better light trapping performance. Through analysis of short circuit current density, unit cells with heart-pentagon polygon arrangement were verified to offer superior absorption in entire silicon absorption spectrum. Finally, the comparisons with other reported textures validated our design. [ABSTRACT FROM AUTHOR]

The small wavelength utilizable range used for determining the optimum performance of photovoltaic and rectenna devices, compared to the broad band spectrum of solar or other heat sources, limits the energy conversion efficiency of such technologies. A selective emitter, with an emissivity profile that matches the receiver's characteristic bandwidth, can be used to improve the overall efficiency of such energy harvesting devices. This paper compares simulated and experimental results of the design and fabrication of a selective emitter that can be used in the 8–12 µm frequency range. The matrix transform method is used to calculate the radiative properties of one dimensional metal-dielectric photonic structures. By using genetic algorithm as a powerful optimization tool, the simulated design characteristics of such structure are adjusted to minimize the mean square deviation of the actual spectral emissivity from the target emissivity profile. Specifically, this paper presents and compares results of the simulated design and fabrication of selective emitters composed of alternating layers of Al 2 O 3 -SiO 2 or Al 2 O 3 -SiC on an aluminum substrate. The output radiation of these selective emitters could be used as the input radiation to high efficiency rectenna devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • High-quality optical filters were produced by sinusoidal pulse anodisation. • Porous anodic alumina (PAA) exhibits an ordered pore structure and high reflectance. • Photonic stop-band in sinusoidal-profiled (PAA) shifts deeper into infrared region. • Polarisation dependence optical features of photonic-stop band were found in PAA. • Pulse anodising between self-ordering regimes enhances porosity contrast. Porous anodic alumina (PAA) holds promise for the realisation of high-quality optical filters with first-order photonic stop-bands (PSB λ1) located in the infrared spectral region, thereby expanding the possibility of its application in photonics and light-based industries. High-temperature (30 °C) sinusoidal pulse anodisation (SPA) of aluminium was applied to fabricate PAA with PSB λ1 in the range of 800–2500 nm. The systematic increase in the anodisation period (t p) and amplitude (A) caused a significant change in the optical properties of the PAAs, which were monitored by both transmittance and reflectance measurements. A switch from gradient-index to step-index optical filters was observed when A and t p were increased from the lowest (5 V and 100 s, respectively) to the highest (15 V and 300 s, respectively) values. The switch was ascribed to the transition between different self-ordering regimes. The finest filtering properties (PSB λ1 reflectance close to 100 %) were achieved when the SPA proceeded between diffusion and kinetic regimes, providing a better porosity/refractive index contrast within the periodic structure. The analysis under polarised light confirmed both the excellent filtering properties of the PAAs and the asymmetrical light reflectance produced through the robust and cost-effective SPA process. [ABSTRACT FROM AUTHOR]

A photonic crystal can be used for controlling light propagation by defining a photonic stop band that is decided by both the periodic structure and material. In this study, the photonic structure in butterfly wing was inversely replicated with germanium dioxide through a facile liquid phase deposition process. Precise replicas of both micro-tile array and dispersed micro-cubes were produced by adjusting the depositing conditions. This work provides the possibility that the abundant photonic crystals in nature can be further enriched by combining the merits of both artificial tailoring and constituents. [ABSTRACT FROM AUTHOR]

The planar orientation of Nematic Liquid crystal (NLC) molecules on the surface of (111) plane of silica photonic structure has been investigated. Nano voids of silica photonic crystal has been obtained by vertical deposition technique on indium tin oxide-coated substrate. NLC was infiltrated into the channels of voids in the photonic structures. Optical texture studies under with and without electric field were applied to investigate the NLC orientation. It is observed that NLC molecules in the nano voids of silica photonic structure exhibit an excellent planar alignment. This obtained hybrid composite structure on infiltration of NLC will be a promising candidate for electro optic applications. [ABSTRACT FROM PUBLISHER]

Abstract: In this study, a novel method of an array of square columns with high aspect ratio (about 10) on quartz and a pattern of complex multi-layered woodpiles on slide glass are firstly fabricated by femtosecond laser inner modification with hydrofluoric acid (HF) etching. The three-dimension (3D) patterns composted with embedded gratings are scribed by femtosecond laser focused inside the bulk materials with the central wavelength of 517nm, the repetition rate of 100kHz, the pulse width of 350fs and the power of 100mW. For the quartz glass, a high aspect ratio (about 10) structure of squared column array with the width of 10μm and the height of 100μm is formed from a grid pattern etched by 15wt% HF for 15min and 5wt% HF for 90min. For the slide glass, a 3D piled-octahedron structure with the feature size of 10μm is developed from a multi-layer woodpile pattern etched by 5wt% HF for 2h. Moreover, the optical band structures of both 3D structures are calculated by the plane wave expansion method. And then, the defect effect of light propagation with sample paths on square and piled-octahedron structures are designed to verify the optical characteristics by finite difference time domain (FDTD) simulation in this study. [Copyright &y& Elsevier]

Abstract: The reflection band characteristics of rugate porous silicon (PS) and the effect of an etching time for the formation of rugate photonic structure were investigated. The reflection band of rugate PS shifted to shorter wavelength by about 30nm as the etching time increased. The effect of frequency for the formation of rugate PS was investigated. The reflection band characteristics of 17 rugate PS samples according to the frequency change were investigated. All parameters but etching frequency were fixed. The values of Ai , B, and t were 11.55 and 63.05mA and 1000s, respectively. The frequencies, ki , varied from 0.22 to 0.38Hz. and the effect of a frequency for the reflection band characteristics of rugate PS were investigated. Rugate PS exhibited a linear dependence between the reflection wavelengths and the etching frequencies. [Copyright &y& Elsevier]

Abstract: We present a light emitting diode with a two-dimensional photonic crystal structure prepared by interference lithography at the light emitting diode surface. The emission maximum is at 850nm. The two-dimensional photonic crystal structure enhanced the light extraction efficiency by a factor of 1.39. The photonic crystal light emitting diode surface morphology was analyzed by atomic force microscopy. The enhanced extraction efficiency of the photonic crystal diode was documented from L(I) dependencies and was confirmed by near-field studies. [Copyright &y& Elsevier]

Abstract: Optical properties of the spinal cuticle taken from the species of Lucilia sericata are studied by the reflectance measurements and their structural properties by scanning electron microscopy. The multilayer structure of the cuticle has been confirmed from the scanning electron micrographs. The temperature sensitivity of the multilayer structure is documented by the modification of optical properties in a heating process. The heating process and the local heating using the focused laser beam causes the local changes of the optical properties what is finally demonstrated by the structural color shift of the reflected spectra. [Copyright &y& Elsevier]

Abstract: In this work, we report on the fabrication and characterization of surface microstructures in lithium niobate thin films and single crystal by using KrF excimer laser ablation technique at 248nm with 6ns pulse width. Ablation is carried out through a mask projection set-up. Various experimental conditions are used in order to evaluate the potential of laser direct writing for photonic waveguides fabrication in lithium niobate. The surface morphology of the processed structures was studied by optical and atomic force microscopy. Laser processing mechanism is investigated by using micro-Raman spectroscopy. [Copyright &y& Elsevier]

It is demonstrated that an isotropic left-handed medium can be constructed as a photonic structure consisting of two dielectric materials, one with positive and another with negative dielectric permittivities ϵ. Electromagnetic waves supported by this structure are the surface waves localized at the dielectric interfaces. These surface waves can be either surface phonon polaritons or surface plasmons. Two examples of negative ϵ materials are used: silicon carbide and free-electron gas. [Copyright &y& Elsevier]

We investigated emission properties of photonic structures with InAs/InGaAlAs/InP quantum dashes grown by molecular beam epitaxy on a distributed Bragg reflector. In high-spatial-resolution photoluminescence experiment, well-resolved sharp spectral lines are observed and single-photon emission is detected in the third telecommunication window characterized by very low multiphoton events probabilities. The photoluminescence spectra measured on simple photonic structures in the form of cylindrical mesas reveal significant intensity enhancement by a factor of 4 when compared to a planar sample. These results are supported by simulations of the electromagnetic field distribution, which show emission extraction efficiencies even above 18% for optimized designs. When combined with relatively simple and undemanding fabrication approach, it makes this kind of structures competitive with the existing solutions in that spectral range and prospective in the context of efficient and practical single-photon sources for fiber-based quantum networks applications. [ABSTRACT FROM AUTHOR]

UV–Vis reflectance spectroscopy, combined with field emission scanning electron microscope (FE-SEM), was used to comparatively characterize nacre areas with milky-white and pink-violet coloration from the same Hyriopsis cumingii shell. Although the mean thicknesses of the aragonite platelets in the nacre from the pink-violet area were similar, the reflection spectra obtained from different locations within this area were not uniform. This indicated that the vivid color appearing on the inner surface of the shell was not completely derived from the one-dimensional photonic structure. We proposed that the absorption peak in the ultraviolet region was associated with carotenoids. The strength of the absorption peak increased with carotenoid concentration. The inner surface of the shell was not flat, leading to obvious frequency shifting in the reflection peak of the violet region. More importantly, our findings suggested that the vivid color of the inner surface of the shell was caused by the combined effects of organic pigment and one-dimensional photonic band. This present study advances our understanding of coloration mechanisms. Furthermore, we expect that our work may provide basis for further studies of pearl culture or quality grading and might inform further investigations of the design and synthesis of advanced functional materials for optical, biomedical, and mechanical applications. • The vivid colors appear only on the inner local area of the inside surface of the Hyriopsis Cumingii shell. • It is proposed that the colors on the inner surface of the shell are caused by carotenoids and one-dimensional photonic band. ,Furthermore, the organic pigment is attributed to the carotenoids in nacre. • The morphologies of the aragonite platelets are very clear in the nacre nearby the milky-color surface. • The reflectance spectroscopy is the predominant tool used to evaluate the quality grade of pearl. [ABSTRACT FROM AUTHOR]

• Optical glucose biosensor with glucose oxidase was developed with a photonic interpenetrating polymer networks (IPN) structure. • Photonic IPN was prepared with solidified cholesteric liquid crystal (CLCsolid) and intertwined poly(2-dimethylaminoethyl methacrylate). • Glucose oxidase's reaction with glucose redshifted the reflected color of the photonic IPN with high sensitivity and selectivity. • The developed glucose biosensor allowed naked-eye detection without any sophisticated analytical instruments. A patterned photonic array of dots with a photonic interpenetrating polymer network (IPN) structure consisting of intertwined photonic solid-state cholesteric liquid crystals (CLC solid) and cationic polyelectrolyte networks was utilized for glucose detection. The photonic CLC solid network was prepared using a reactive mesogen mixture (RMM 727, Merck) doped with the chiral dopant CB15 1 1 (S)-4-cyano-4´-(2-methylbutyl)biphenyl (CB15) , followed by ultraviolet (UV) curing and chiral dopant extraction. The networked cationic polyelectrolyte was prepared by infiltrating a monomer mixture of DMAEMA 2 2 2-dimethylaminoethyl methacrylate (DMAEMA) and acrylic acid (AA) (85:15 mol%) and a crosslinker of TPGDA 3 3 Tripropylene glycol diacrylate (TPGDA) into the extracted space of the CLC solid network, UV curing under a photomask, washing the unreacted monomers outside the dots, and immobilizing the glucose oxidase (GOx) at the AA units via a coupling reaction with EDC 4 4 N-(3-dimethylaminopropyl)-N-ethylcarbodiimide (EDC). The prepared patterned photonic dots display a clear pH response in terms of a redshift with decreasing pH because the intertwined poly(DMAEMA) (PDMAEMA) is a typical weak cationic polyelectrolyte which protonates and expands at pH values below its pK b. Thus, the enzymatic reaction of GOx with glucose causes a decrease in pH, expansion of the PDMAEMA, and a redshift of the reflected photonic color. The optimized photonic optical sensor shows a linear range of 0.7–12 mM with a detection limit of 0.021 mM, superior selectivity, and excellent spike test results with real blood serum. The developed photonic IPN sensor is attractive because it is cost-effective, battery-free, and allows easy naked-eye optical detection without the need for sophisticated analytical instrumentation. [ABSTRACT FROM AUTHOR]

The intrinsic effects of the microstructures on the responsive properties of photonic crystals were experimentally investigated by coupling polyacrylamide on three kinds of biotemplates based on butterfly wings. The conclusion is supported by the simulation results of FDTD, which paves a new avenue to design the responsive PCs with a diversity of structures from nature and controllable responsive properties. • Humidity responsive PCs were fabricated by using PAAm as the water absorbing agent and natural photonic structured butterflies as templates. • Using the finite-different time-domain (FDTD) method to reveal the mechanism of the influence of structures on responsive properties. • Papilio paris butterflies could have higher sensitivity to refractive index changes than the Morpho butterflies. Nature provides abundant photonic structures which give a great inspiration on the synthesis of stimuli-responsive photonic crystals (PCs) with unique structures. However, the intrinsic effects of microstructures on the responsive properties of the hierarchical PCs are still not clear. Herein, the relationship between the photonic structures and the responsive properties is investigated by choosing three natural photonic structures replicated from templates, Morpho Menelaus and Morpho peleides both with a 1D tree-like hierarchical structure while having eight and four layers, respectively and Papilio paris , with an eight layered 1D concave structure. Humidity responsive PCs were prepared by in-situ polymerizing polyacrylamide (PAAm) onto the surface of the butterfly wing scales. The 1D concave (Papilio paris) structured PCs exhibited a higher humidity sensitivity: a wavelength redshift of 92 nm when the relative humidity rose from 11 to 97 %, as compared with the Morpho menelaus PCs, which have about 70 nm redshift for the same rise of the relative humidity. The eight layer 1D tree-like structured Morpho menelaus PCs had a higher reflectance intensity. The results were also supported by a finite-difference time-domain (FDTD) simulation. This work paves a new avenue to design responsive PCs with a diversity of structures from nature and controllable responsive properties. [ABSTRACT FROM AUTHOR]

Optical modes of a multilayered photonic structure with the twisted nematic liquid crystal as a defect layer have been investigated. The electroconvective flow in the nematic makes a spatially periodic structure in the form of abnormal rolls. Non-adiabatic propagation of polarized light in the defect layer causes unique features of the optical modes corresponding to the ordinary o -waves. The decay of these modes has been demonstrated with increasing voltage due to the effect of cross-polarization diffraction loss. The modes short-wave shift resulting from the contribution of the non-adiabatic geometric phase to the total phase delay of the wave during a round-trip propagation through the photonic structure has been found both experimentally and numerically. • Multilayered photonic structure with convective rolls in nematic layer was studied. • Electrically induced abnormal rolls effect on defect modes in photonic bandgap. • Increasing control voltage causes monotonic decay of defect modes. • Violation of adiabatic propagation of light leads to short-wave shift of the o -modes. [ABSTRACT FROM AUTHOR]

Both vertebrates and invertebrates commonly exploit photonic structures adjacent to their photoreceptors for visual benefits. For example, use of a reflecting structure (tapetum) behind the retina increases photon capture, enhancing vision in dim light [ 1–5 ]. Colored filters positioned lateral or distal to a photoreceptive unit may also be used to tune spectral sensitivity by selective transmission of wavelengths not absorbed or scattered by the filters [ 6–8 ]. Here we describe a new category of biological optical filter that acts simultaneously as both a transmissive spectral filter and narrowband reflector. Discovered in the larval eyes of only one family of mantis shrimp (stomatopod) crustaceans (Nannosquillidae), each crystalline structure bisects the photoreceptive rhabdom into two tiers and contains an ordered array of membrane-bound vesicles with sub-wavelength diameters of 153 ± 5 nm. Axial illumination of the intrarhabdomal structural reflector (ISR) in vivo produces a narrow band of yellow reflectance (mean peak reflectivity, 572 ± 18 nm). The ISR is similar to several synthetic devices, such as bandgap filters, laser mirrors, and (in particular) fiber Bragg gratings used in optical sensors for a wide range of industries. To our knowledge, the stomatopod larval ISR is the first example of a naturally occurring analog to these human-made devices. Considering what is known about these animals' visual ecology, we propose that these reflecting filters may help improve the detection of pelagic bioluminescence in shallow water at night. • Reflective filters in mantis shrimp larvae simultaneously reflect and transmit light • Reflecting filters are predicted to aid in detecting bioluminescent targets • Only one mantis shrimp family possesses these unusual filters • The filters are a natural analog of synthetic fiber Bragg gratings Feller et al. report how one family of mantis shrimp larvae uses visual filtering structures to selectively reflect and transmit light within photoreceptors. These reflective filters likely enhance bioluminescence detection underwater at night and are similar to human-made optical devices such as fiber Bragg gratings or band gap filters. [ABSTRACT FROM AUTHOR]