2D Photonic Crystal Structures Research Articles

A machine learning-based biomedical sensor with help of 2D photonic crystal structure

A machine learning-based biomedical sensor with help of 2D photonic crystal structure

Bio‐Inspired Camouflage Skin with Photonic Crystal Structure and Size‐Confinement Effect

AbstractCamouflage skin holds immense potential for a variety of advanced applications, such as artificial intelligence, soft robotics, and flexible/wearable electronics. Currently, most existing materials for constructing camouflage skin are mainly based on inorganic materials with an inverse opal scaffold, which significantly limits their further development because of the poor mechanical properties and environmental instability. Inspired by rana slvaticas, a new type of camouflage skin based on one‐dimentional (1D) photonic crystal (PC) gel is designed and synthesized, which combines the advantages of 1D PC structures with 3D flexible gels in a single skin device. Taking advantage of the unique structures, the resulting camouflage skins demonstrated attractive properties, including excellent mechanical performance, self‐adaptive camouflage capabilities, and long‐term stability in ambient conditions. Specifically, the camouflage skin can quickly recognize and match the background by modulating the optical signals of external stimuli. The synergistic effect of the glycerol, the dodecyl glycerol itaconate (DGI), and the nano‐space structures altogether contribute to the outstanding long‐term environmental stability of the camouflage skin. Overall, by combining the bio‐inspired concept and molecular engineering strategy, camouflage skin based on PC gels is synthesized, which greatly enriched the application and development in the smart skins field.

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

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

Genetic Optimization of the Y-Shaped Photonic Crystal NOT Logic Gate

The present paper is devoted to the actual problem of photonic crystal (PhC) logic gate design. The development of components for photonic digital computing systems will provide opportunities for high-efficient information processing. The use of 2D photonic crystals is one of the most promising approaches to designing interference logic gates. Photonic crystal band gap and use of lattice defects are giving opportunities for flexible control of waveguiding light. Interference logic gates of NOT, OR, AND, and XOR types based on the Y-shaped structure are well known. However, known realizations have limited energy efficiency. Earlier, a method for minimizing energy losses at the PhC waveguide bending based on genetic optimization of the PhC waveguide topology was proposed and investigated. In this paper, the genetic algorithm for optimization of the PhC interference logic gate of the NOT type was used. Optimization of the Y-shaped topology allowed for an increase in the energy efficiency of the logic gate to 95%. A description of the developed numerical procedure as well as computer simulation results are presented. The developed procedure includes the possibility of taking into account the limitations of the technology to be used for the realization of a designed 2D PhC structure.

Near-perfect wide-band absorbers based onone-dimensional photonic crystal structures in1-20 THz frequencies.

This paper investigates the absorption behavior of one-dimensional (1D) photonic crystal (PhC) structures in the 1-20THz region. The structures are analyzed by the transfer matrix method to achieve accurate results quickly with ordinary simulation facilities. The simulation results indicate a strong dependence of the absorber performance on the thickness and material of the PhC layers, as well as the frequency and angle of incident light. The combination of silica and titanium (Ti) materials as dielectric and metal layers presents a great choice for broadband high-absorption applications so that this structure can absorb, on average, more than 80% of the normal incident radiation in the studied frequency range. Additionally, this absorber has the lowest dependence on incident light with the angle varying from 0° to 80° compared to identical absorbers with silver, aluminum, gold, chromium, nickel, and tungsten metals. The excellent absorption feature of the Ti-based absorber compared to the other absorbers is attributed to the lower permittivity of Ti (in both real and imaginary parts) in comparison with the other metals. In addition to owning simple and fabrication-friendly structures, 1D PhCs can pave the way to achieve various absorption spectra proportional to the needs of photonics, communications, and aerospace applications.

Amplification of near field radiation at surfaces of pure dielectric domain with anti-reflection films and photonic crystal structures

With chemical stability under high temperatures, dielectric materials can be idealized thermal emitters for different energy applications. However, dielectric materials do not support surface waves at near-infrared ranges for longer-distance thermal photon tunneling, which limits their applications in near-field thermal radiation. It is demonstrated in this study that thermal field amplification at near-infrared wavelengths at dielectric surfaces could be achieved through asymmetric Fabry–Perot resonance with anti-reflection coatings or 1D photonic crystal type structures. ⩾100 nm near-infrared thermal photon tunneling can be achieved when these thin film structures are added to the emitter and the collector surfaces. Among these two thin film structures, 1D photonic crystal type periodic structures constructed with the same high refractive index material as the emitter/collector material allow near-field thermal photon tunneling at large parallel wavenumbers. Moreover, the field amplification can be increased by adding more 1D photonic crystal layers to achieve even longer distances near field thermal photon tunneling.

Computational study of 2D photonic crystal based biosensor for SARS-COV-2 detection

A computational study to design a 2D-photonic crystal (PC) structure with a fluorescence-based biosensor has been demonstrated for the detection of the severe acute respiratory syndrome corona virus 2 (SARS-COV-2) virus in the lungs. The proposed sensor can detect the different concentrations of the virus without any pretreatment of the sample. The virus detection is performed by measuring the mid-gap wavelength from the dispersion diagram and a redshift in the mid-gap wavelength has been observed as the concentration of virus increases in the lung tissue. The plane wave expansion method is used to determine the dispersion diagram of the proposed PC. The interaction of incident light with the proposed PC-based biosensor has been analyzed to evaluate the shift in the mid-gap wavelength. A maximum sensitivity of about 1459.3 nm/RIU is obtained for r/a = 0.45 with a mid-gap wavelength shift of 145.93 nm at = 1.49 concentration of SARS-COV-2. Moreover, a very small detection time has been observed with the proposed device as compared to conventional methods. This study provides a simple process to detect the presence of a virus within a short period and could be helpful in the development of a direct and easy-to-use portable detection kit in the future.

Monolithically integrated photonic crystal surface emitters on silicon with a vortex beam by using bound states in the continuum.

Optical resonant cavities with high quality factor (Q-factor) are widely used in science and technology for their capabilities of strong confinement of light and enhanced light-matter interaction. The 2D photonic crystal structure with bound states in the continuum (BICs) is a novel concept for resonators with ultra-compact device size, which can be used to generate surface emitting vortex beams based on symmetry-protected BICs at the Γ point. Here, to the best of our knowledge, we demonstrate the first photonic crystal surface emitter with a vortex beam by using BICs monolithically grown on CMOS-compatible silicon substrate. The fabricated quantum-dot BICs-based surface emitter operates at 1.3 µm under room temperature (RT) with a low continuous wave (CW) optically pumped condition. We also reveal the BIC's amplified spontaneous emission with the property of a polarization vortex beam, which is promising to provide a novel degree of freedom in classical and quantum realms.

Study on the transmission characteristics and band structure of 2D and 3D plasma photonic crystals.

In this paper, 2D and 3D plasma photonic crystals (PPCs) were constructed using argon-mercury glow discharge tubes. Firstly, the collisional radiative model (CRM) was established for the glow discharge process, the average electron density of plasma in the discharge tube was calculated, and the average electron density was experimentally diagnosed by microwave diagnosis. By comparing the calculated and experimental results, the variation range of the average electron density in the tube was given. Secondly, according to the analysis results of the average electron density, a layered model of the discharge tube was established, and the transmission characteristics of the 2D and 3D PPC were calculated and measured. Finally, to analyze the cause of the photonic bandgap (PBG) in the transmission spectra, the band structures of 2D and 3D PPC were calculated using the plane wave expansion (PWE) method and the symplectic finite difference time domain (SFDTD) method. The results show that: the layered model is a valid discharge tube model; for 2D PPC, the formation of Localized Surface Plasmons (LSPs) under TE polarization is the main cause of PBG generation, and the number of LSP bandgap increases as the electron density rises; The existence of cutoff bandgap under TM polarization is due to the cutoff effect of plasma on electromagnetic waves. For 3D PPC, both cutoff bandgap and LSP bandgap exist in the transmission spectra, and the cutoff bandgap is shifted to lower frequencies due to the presence of Fano mode. The results of the study can be used as a reference for communication, microwave device fabrication, and military target stealth.

Design and investigation of 1D photonic crystal based structures for BIPV cell colorization by sol-gel dipping technology

The growth of the building integrated photovoltaic (BIPV) sector is limited by the apparent lack of ways to create the visual impact of the building at acceptable cost efficiency rates in the current PV market. Thus, in this research digital simulations were combined with experimental studies to design and optimize novel 1D photonic crystal structures acceptable to expand and improve the color palette of PV panels. It was proved that the 3-layered system with TiO2/SiO2/TiO2 was both efficient and sufficient for this purpose. Advanced light filtering was implemented experimentally on 5x5 size glass plates with a potentially cheap and simple sol–gel dipping technique with annealing only at 110 °C. The applicability of the proposed technology was validated by manufacturing the PV mini panels that showed 2–3 higher brightness in CIE color space compared to the panels made using commercial solar cells. Experimentally obtained efficiencies were: 18.75% (REF, black), 17.28% (light blue), 17.13% (greenish), 16.52% (yellowish), which is in the range to the commercial colored cells, but could be higher if better cells were used. The technology reliability and scalability were evaluated from analysis of the sensitivity of the 1D photonic crystal parameters to the optical properties of the colored device. The tolerable deviations from the color related numbers are approximately +/- 0.05 for the refractive index spectrum and less than approximately +/- 2% for the thickness. Therefore, the proposed coloring method should be a perspective solution for BIPV, but careful attention should be taken for the technological process optimization.

An angle-compensating colorimetric strain sensor with wide working range and its fabrication method

The visual response is one of the most intuitive principles of sensors. Therefore, emission and change of the colors are widely studied for development of chemical, thermal and mechanical sensors. And it is still a challenging issue to fabricate them with a simple working mechanism, high sensitivity, good reliability, and a cost-effective fabrication process. In this study, we propose a mechanical strain sensor, which has 2D photonic crystal structures in nanoscale on stretchable polydimethylsiloxane (PDMS) substrate. Due to the periodic nanostructures, the surface of the sensor produces structural colors. And when it is stretched, the periodicity of the nanostructures changes, which results in the shift of the colors. Multiple nanostructures with different periodicities are integrated on the sensor in order to extend the working range up to 150% with high sensitivity. In addition, reusable and robust molds, which are fabricated by self-assembly of nanoparticles, are used for multiple replications of sensor substrates. Thus, the fabrication process of this study is believed to be potential for possible industrial manufacturing. This study is expected to contribute to strain sensors in the future for the applications of health care, infrastructure monitoring, soft robotics, and wearable devices.

The impact of magnetized cold plasma and its various properties in sensing applications

These analyses present a novel magnetized cold plasma-based 1D photonic crystal structure for detecting the refractive index of various bio-analytes. The proposed structure is designed with two photonic crystals composed of an alternating layer of right-hand polarization and left-hand polarization of the magnetized cold plasma material with a central defect layer. Transmittance characteristics of the structure are studied by employing the well-known transfer matrix method. Various geometrical parameters such as electron density, external magnetic field, thickness of odd and even layers of the multilayers, thickness of the sample layer, and incident angle are judiciously optimized to attain the best sensitivity, figure of merit, quality factor, signal-to-noise ratio, detection range and limit of detection. Finally, a maximum sensitivity of 25 GHz/RIU is accomplished with the optimized value of structure parameters, which can be considered as a noteworthy sensing performance.

Performance analysis of all optical 2 × 1 multiplexer in 2D photonic crystal structure

Abstract In optical processing systems, multiplexer is used to design optical devices such as arithmetic logic unit (ALU) and shift register (SR). Through this paper, we investigate the application of nonlinear photonic crystal ring resonator (PhCRR) based on nonlinear Kerr effect for realizing an all optical 2 × 1 multiplexer. The structure consists of two PhCRRs and five optical waveguides using hexagonal lattice silicon (Si) rods with a background of air. Performance of all optical 2 × 1 multiplexer is replicated with the help of finite difference time domain (FDTD) procedure at a wavelength of 1571 nm, and simulations presented an ultra-compact optical structure with ultra-fast switching speed.

A new one-dimensional photonic crystal magnetic sensor based on magnetic fluid film with excellent sensing ability and figure of merit

A magnetic sensor based on a one-dimensional (1D) photonic crystal was proposed. The transmission characteristics of the 1D photonic crystal magnetic sensor were analyzed using the theory of rigorous coupled wave analysis (RCWA). The variation pattern of magnetic fluid films refractive index with magnetic field and the effect of structural parameters on sensitivity and figure of merit (FOM) were investigated. Based on the wavelength interrogation method, the resonance wavelength is red-shifted with the change of the magnetic field for certain structural parameters. The results show that the structure has a highly linear response within the external magnetic field variation range from 30 Oe to 90 Oe, and its sensitivity and FOM can reach 0.817 nm/Oe and 17.439 Oe−1. Due to the advantages of 1D photonic crystal structure has harp peak, highly linear response, and low transmission loss. The structure has a large potential for applications in complex environments and real-time monitoring.

An Ultra-Sensitive 1D Photonic Crystal BioNEMS Platform for Label Free Detection of Biomolecules

In this paper, we present a novel optical BioNEMS (Biological-Nano-Electro-Mechanical Systems) sensor based on a 1D photonic crystal (PhC) structure in order to develop a label free biosensing platform. The proposed biosensor consists of a BioNEMS cantilever as the tunable defect of the PhC detection part. This optical sensing system is a finite air hole photonic crystal with a nano air gap in the center of the structure so that the NEMS movable part can be freely displaced. Biomolecular interactions induce a surface stress on the functionalized surface of the movable structure. As a consequence, a nanomechanical bending occurs in the NEMS cantilever because of the released energy of binding events. This can change the defect of the proposed PhC which causes shifts in the transmitted wavelength for various concentrations of biomarkers. By analyzing the proposed device using numerical and analytical approaches, the functional characteristics of the present BioNEMS sensor are obtained as follows: optical sensitivity of 13452 nm/RIU, FOM of 7912 RIU <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> , mechanical sensitivity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4.6~\mu \text{m}$ </tex-math></inline-formula> /Nm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> and resonant frequency of 33.3 kHz. According to the results, this ultra-high sensitive sensor can be a promising choice to realize efficient label-free biosensors for early diagnoses of diseases in Point-of-Care Testing (POCT).

Theoretical Model for a Highly Sensitive Near Infrared Biosensor Based on Bloch Surface Wave with Dirac Semimetal.

In this work, we present a theoretical model of a near-infrared sensitive refractive index biosensor based on the truncate 1D photonic crystal (1D PC) structure with Dirac semimetal. This highly sensitive near-infrared biosensor originates from the sharp reflectance peak caused by the excitation of Bloch surface wave (BSW) at the interface between the Dirac semimetal and 1D PC. The sensitivity of the biosensor model is sensitive to the Fermi energy of Dirac semimetal, the thickness of the truncate layer and the refractive index of the sensing medium. By optimizing the structural parameters, the maximum refractive index sensitivity of the biosensor model can surpass 17.4 × 103/RIU, which achieves a certain competitiveness compared to conventional surface plasmon resonance (SPR) or BSW sensors. Considering that bulk materials are easier to handle than two-dimensional materials in manufacturing facilities, we judge that 3D Dirac semimetal and its related devices will provide a strong competitor and alternative to graphene-based devices.

(INVITED) Tungsten oxide films by radio-frequency magnetron sputtering for near-infrared photonics

Tungsten oxide WO3-x is a transition metal oxide and a wide bandgap semiconductor, with a wide range of possible optical and photonic applications. In dependence on the fabrication techniques different stoichiometric ratios (x) and crystalline phases are obtained, which end up with an overall polymorph and extremely versatile material, characterized by tailorable dielectric properties. In particular, WO3-x thin film deposition by Radio-Frequency (RF) sputtering techniques provides a precise control of thickness, composition and nanostructure. In this work we introduce and discuss a specific process of deposition, that is magnetron RF-sputtering as a suitable way to grow WO3-x thin films with selected properties. Possibility of integrating WO3-x thin film on to one-dimensional (1D) photonic crystal structures is also explored. Films are transparent in the near and short-wavelength infrared optical spectral range. Their quality is assessed by morphological, structural and compositional characterizations. Dielectric properties are characterized by optical spectroscopy and ellipsometry, the latter also evaluates the degree of optical anisotropy of thin films in their crystalline phase. An 1D photonics bandgap structure is designed, formed by a SiO2–TiO2 multilayer and capped with a 450 nm-thick transparent WO3-x film, so that surface confinement and local enhancement of the optical field at 1416 nm in the topmost WO3-x layer is obtained.

Nano-imprinted anisotropic structural color graphene films for cardiomyocytes dynamic displaying

Cellular mechanics plays an important role in physiological processes such as cell growth, differentiation, apoptosis and gene expression. Herein, we present a nano-imprinted structural color graphene film with anisotropic microgroove and two-dimensional (2D) photonic crystal structures for cardiomyocytes dynamic displaying. The anisotropic structural color graphene film was generated by a “sandwich” mold in one step with the assistance of two designed templates. Because of the microgroove structure and biocompatibility of the film, the cardiomyocytes could be induced into a highly ordered arrangement with recoverable autonomous beating. Meanwhile, the opposite surface of the film was imparted with defect-free 2D photonic crystal structures, giving it a vivid structural color and photonic band gap (PBG). We demonstrated that the flexible film would undergo synchronous volume or shape changes with the cardiomyocytes’ elongation and contraction during the beating process, showing cyclic changes of the structural color, which in turn could be converted into force. In addition, by integrating this anisotropic structural color graphene film with microfluidic channels, a novel and accurate heart-on-a-chip platform was established for real-time cell monitoring and drug screening. These characteristics of the present anisotropic structural color graphene films make them extremely valuable in the field of biomedicine.

Fabrication of robust and reusable mold with nanostructures and its application to anti-counterfeiting surfaces based on structural colors

In this study, we report a method to fabricate molds and flexible stamps with 2D photonic crystal structures. This includes self-assembly of polystyrene particles into monolayer, oxygen reactive ion etching, thin film (chromium (Cr)) deposition, and polydimethylsiloxane replication. By tuning the thickness of Cr layer, reusable master molds with nano bumps or nano concaves could be prepared selectively. We showed that the replicated flexible stamps out of these molds exhibited structural colors. Characteristics of the colors depended on viewing angle, brightness of background and light source. And the colors even faded out when the background is white or when the stamp was bent. By using this feature, possible strategies for anti-counterfeiting applications have been suggested in this study. Since the molds are reusable and the fabrication method is simple and cost-effective, this study is expected to contribute to nano devices for industries in future.

Realization of 3D reflectors by using metal-air and semiconductor-air based photonic structures at three communication windows

This study is based on analysis of 3D photonic crystal structure (PCS) for realization of photonic reflector pertaining to suitable optical communication wavelengths of 850, 1310 and 1550 nm. The said photonic reflector application is envisaged separately by two 3D PCSs, which comprise semiconductor (germanium) and metal (iron) based circular rods respectively, arranged on a square lattice having air as the background material. The plane wave expansion (PWE) technique is employed to investigate the photonic band gap (PBG) vis-à-vis all the aforementioned wavelengths. PBG is meticulously controlled by suitably selected various structure parameters, such as lattice spacing, diameter of the circular rods and nature of their material. Simulation outcomes explored that semiconductor based PCS reflects wavelengths of 850, 1310 and 1550 nm, when selecting the diameter of the circular rods as 282, 608 and 771 nm, respectively, whereas metal based PCS reflects the aforementioned wavelengths for diameters of the circular rods close to 335, 1070 and 871 nm, respectively. Further, we assayed the variation in reflected wavelength with respect to different diameters of circular rods for both proposed structures. Thus, the proposed optical reflectors can find a wide range of applications vis-à-vis three communication windows.