Change Of Incident Angle Research Articles

A miniaturized transmission/absorption integrated frequency selection surface with ultra‐wide absorption band

In this paper, a miniaturized integrated frequency selective surface (FSS) is proposed. It is composed of two parts: the band-stop FSS and band-pass FSS. Through introducing six capacitors between the hexagonal gap of band-pass FSS, a miniaturized dimension of 0.07λ0 × 0.07λ0 × 0.036λ0 (λ0 is the wavelength of the transmission band in free space) is achieved. As a result, the presented FSS effectively avoids grating lobes and remains stable when the incident angle changes. In addition, by coupling between the band-stop and band-pass FSSs, the ultra-wide-band absorption is realized. The results show that the insertion loss at 2.2 GHz is only 0.6 dB and the bandwidth with the absorptivity larger than 90% is 12.6 GHz (6.8–19.4 GHz). Besides, the integrated FSS has good polarization and angular stability.

Gas sensing applications using magnetized cold plasma multilayers

In this paper, we theoretically propose a novel magnetic field-dependent sensor using omnidirectional magnetized cold plasma photonic crystal in one dimension for TE polarization. The structure consists of asymmetric two periodic arrays from magnetized cold plasma and sample cavity layer. Between the periodic arrays, a sample cavity is sandwiched between two quartz layers. The methodology of the proposed detector depends on the appearance of a sensitive defect mode. The results clear that the defect mode frequency depends significantly on the refractive index of the sample, and it is extremely sensitive to incident angle changes, applied magnetic field, the number density of electrons, and sample layer thickness. The optimized proposed sensor has high sensitivity of 15.14 GHz/RIU, quality-factor of 527.32, and figure of merit of 1066.20 RIU−1, where RIU means refractive index unit. So, the proposed sensor can aid in solving many challenges in chemical and environmental applications.

MATLAB Simulation-Based Theoretical Study for Detection of a Wide Range of Pathogens Using 1D Defective Photonic Structure

The present 1D photonic biosensor is composed of two sub-PhCs of alternate layers made of GaP and SiO2. The period number of each PhC has been fixed to 3. Both these PhCs are joined together through a cavity region of air in which different analytes are to be filled one by one under the scope of this study. The theoretical findings of this work have been formulated with the help of the well-known transfer matrix method. Moreover, all the computations pertaining to this work have been carried out with the help of MATLAB software. The effect of change in cavity thickness and angle of incidence corresponding to a TE wave on the transmittance of the structure (AB)ND(AB)N has been studied theoretically which in turn determines the performance of the proposed biosensor. Various parameters, such as sensitivity (S), signal to noise ratio (SNR), figure of merit (FOM), resolution (RS), detection limit (LOD), quality factor (Q) and dynamic range (DR) have been theoretically calculated to evaluate the performance of the proposed design in true sense. The sensitivity of this structure varies between the highest and lowest values of 337.3626 nm/RIU and 333.0882 nm/RIU corresponding to water samples containing Pseudomonas aeruginosa cells and Bacillus anthracia cells, respectively, under normal incidence condition with a cavity thickness of 2.0 µm. The resolution (in nm) and LOD (in RIU) values of the proposed design are small enough and are significant for our structure. This study may also be helpful for distinguishing various microbiological samples under investigation and find suitable applications for discriminating bacterial cells from spores.

A high-efficiency wideband tunable polarization conversion metasurface assisted by the localized surface plasmon resonances

Combined with the Dirac semimetals (DSMs), which is a new type of material and also called as 3D graphene, a tunable wideband terahertz polarization conversion metasurface based on an anisotropic configuration is studied, in which the DSMs wire array is beneficial to the regulation of Fermi energy. The results show that the metasurface can realize wideband and highly efficient polarization conversion, and has the property of half wave plate at the resonant modes. This characteristics are derived from the excitation of Localized Surface Plasmon Resonances (LSPRs) and the anisotropy of structure itself. When the incident angle changes in the range of 0°~40°, the high efficiency of wideband polarization conversion can be maintained. When it is greater than 40°, the wideband polarization conversion gradually changes to the dual-band or the multi-band conversion. Furthermore, it is found that in the process of increasing the Fermi energy of AlCuFe from 65 meV to 140 meV, the polarization conversion ratio can be maintained at a high level, and the conversion performance changes from single-band conversion to wideband conversion, and then to wideband conversion with wider band and single-band conversion with narrower band. At the same time, by discussing the metasurface combined with the different DSMs, it is concluded that the better the metallic property of DSMs is, the better the wideband polarization conversion performance of the corresponding metasurface is. At last, the numerical results are verified by the Multiple Interference Theory (MIT) based on the Fabry-Pérot-like resonance cavity.

Pressure coefficient analysis for a setback building

The design of tall buildings is heavily influenced by wind flow characteristics which pose a greater challenge to designers, engineers, and architects. For understanding the wind loads and their effects on the building Computational Fluid Dynamics (CFD) tools are widely used. This paper focuses on the Coefficient of pressure along the circumference at two different elevations for a 7.5% setback provided from all sides at two different elevations using the k- ε model. For the validation of this study, the analysis is first done over a rectangular calibrated model with the same height and base area as that of the setback model and the results of the pressure coefficient are compared with the Indian standard code IS 875 (Part 3): 2015. Variation of Cpe along circumference is observed with a change in wind incident angle from 0 ° to 90 ° for an interval of 30°.

Pressure coefficient analysis for a setback building

The design of tall buildings is heavily influenced by wind flow characteristics which pose a greater challenge to designers, engineers, and architects. For understanding the wind loads and their effects on the building Computational Fluid Dynamics (CFD) tools are widely used. This paper focuses on the Coefficient of pressure along the circumference at two different elevations for a 7.5% setback provided from all sides at two different elevations using the k- ε model. For the validation of this study, the analysis is first done over a rectangular calibrated model with the same height and base area as that of the setback model and the results of the pressure coefficient are compared with the Indian standard code IS 875 (Part 3): 2015. Variation of Cpe along circumference is observed with a change in wind incident angle from 0 ° to 90 ° for an interval of 30°.

Numerical simulation of single-event effects in fully-depleted silicon-on-insulator HfO<sub>2</sub>-based ferroelectric field-effect transistor memory cell

Ferroelectric field-effect transistor (FeFET) memory is currently a popular non-volatile memory. It has many advantages such as nonvolatility, better scalability, energy-efficient switching with non-destructive read-out and anti-radiation. To promote the application of FeFET in radiation environments, the single-event transient effect in HfO<sub>2</sub>-based fully-depleted silicon-on-insulator (FDSOI) FeFET memory cell is studied by technology computer aided design (TCAD) numerical simulation. The effects of different incident positions and angles of heavy ions and the drain bias voltage on the characteristics of the memory cell are analyzed. The results show that the corresponding polarization state in the HfO<sub>2</sub> ferroelectric layer will not reverse regardless of the change for the incident position of heavy ions, but the transient change of the output voltage for the memory cell will be affected. The most sensitive area is close to the drain-body junction area. Moreover, with the decrease of the ion incidence angle, the peak of output voltage for the memory cell increases. And the effect of the incident angle change is more obvious when reading data is “0” rather than “1”. The peak of output voltage for the memory cell is modulated by the drain bias voltage, and the modulation effect is more obvious when reading data is “1” rather than “0”. The above findings provide theoretical basis and guidance for the anti-single event design of the FDSOI FeFET memory cell.

Multiangle Patterned Photonic Films Based on CdS and SiO2 Nanoparticles for Bar Code Applications

This paper proposes a patterned material composed of two types of photonic crystals based on CdS and SiO2 nanoparticles. We combined the photonic crystals with poly(ethylene glycol) diacrylate (PEGDA) by nanoparticle self-assembly and UV curing and successfully formed a material containing the different photonic crystals. The material prepared contains two kinds of photonic crystals with different refractive indices, CdS and SiO2 nanoparticles, and due to the large difference in refractive indices of the two materials, the reflection wavelengths of the photonic crystals composed of the two materials also have disparities when the incident angle changes. Macroscopically, the structural colors of the two photonic crystals change with the change in incident angle. In response to this phenomenon, we designed a variety of applications based on a multiangle patterned photonic crystal film to achieve a variety of information storage functions by changing the incident angle and, through the angle change, to achieve lipstick logo, mobile phone bar code, and antipeeping keyboard applications.

Detection of Reproductive Hormones in Females by Using 1D Photonic Crystal-Based Simple Reconfigurable Biosensing Design

In this manuscript, we have explored the photonic biosensing application of the 1D photonic crystal (PhC) (AB)NCDC(AB)N, which is capable of detecting reproductive progesterone and estradiol hormones of different concentration levels in blood samples of females. The proposed structure is composed of an air cavity surrounded by two buffer layers of material MgF2, which is sandwiched between two identical 1D sub PhCs (AB)N. Both sub PhCs are made up of alternate layers of materials, SiO2 and Si, of period 5. MATLAB software has been used to obtain transmission characteristics of the structure corresponding TE wave, only with the help of the transfer matrix method. The mainstay of this research is focused on the dependence of the intensity and position of the defect mode inside the photonic bandgap with respect to reproductive hormone concentrations in blood samples, change in the thickness of the cavity region and change in angle of incidence corresponding to TE wave only. The proposed design shows high sensitivity of 98.92 nm/nmol/L and 96.58 nm/nmol/L when the cavity of a thickness of 340 nm is loaded with progesterone and estradiol hormones of concentrations of 80 nmol/L and 11 nmol/L, respectively, at an incident angle of 20°. Apart from sensitivity, other parameters such as quality factor and figure of merit have also been computed to gain deep insight about the sensing capabilities of the proposed design. These findings may pave the path for the design and development of various sensing devices capable of detecting gynecological problems pertaining to reproductive hormones in females. Thus, the simple design and excellent performance makes our design most efficient and suitable for sensing applications in industrial and biomedical fields.

2D seismic response of shallow sandy basins subjected to obliquely incident waves

Under the effects of the near-field earthquakes, the change in the incident angle of the incoming wave changes the symmetric response of basins to asymmetric. This paper investigates the 2D response of shallow trapezoidal sandy basins to incident plane SV waves. To attain this goal, a trapezoidal basin with 100 m depth, as the representative of shallow sedimentary basins, with an inclined bedrock angle of 10° was selected. These values fall inside of the ranges of the shallow basin depth and bedrock angle of several real basins. To make the results useful in engineering affairs, three different sand types belonging to the different class of soils, with respect to the soil classification codes, were selected. The constructed models were subjected to the collection of 24 earthquakes with different PGA's of 0.1, 0.2, 0.3 and 0.4 g using a fully nonlinear method. The results showed that the change in the incident angle of the motions not only affects the response at two basin edges but also influences the response of the central part. Among different sandy basins, the behavior of the basin with medium dense sand is less affected by the change in the wave incident angle. For basin with loose sand, while greater maximum spectral amplifications happen at the backward direction of the basin, the forward direction is less affected by the change in the wave incident angle. A different pattern was seen for basin with dense sand. Greater maximum spectral amplifications were seen at the forward direction of the basin. Regarding the effect of motion incident angle on the amplification frequency of shallow basins, it was seen that in case of the obliquely incident waves the spectral amplification curves of the points close to the edges have more than one (generally two) maximum points. Besides, unlike the vertical incident wave case that the SAF curves tend to almost one curve at the distant points from edges, no convergence among the SAF curves of the surface points was seen for the obliquely incident wave condition.

Design of assembly‐type frequency selective surface structure using Lego‐type blocks

AbstractA frequency selective surface (FSS) structure was designed using Lego blocks, which can be stacked or assembled to produce various structures. The unit structure of the designed frequency selection surface structure is a patch‐type cross‐dipole and a dipole structure that can be easily fabricated using Lego‐type blocks among the basic structures. Since the unit structure is designed using Lego‐type dielectric blocks and metal blocks, the structure can be easily changed and the resonance frequency can be easily reconfigured. The designed unit structure was fabricated using actual Lego‐type blocks of 4 mm × 4 mm × 5 mm, and the transmission coefficient of the fabricated FSS structure using the free space measurement method was measured. When the measurement result according to the change of polarization and incident angle was compared with the simulation result, the error of the resonance frequency was 1.2% and 0.64% at the maximum for each structure, confirming that the measurement result is relatively similar to the simulation result.

Multi-Band Polarization Insensitive Ultra-Thin THz Metamaterial Absorber for Imaging and EMI Shielding Applications

this article, a multi-band polarization-insensitive metamaterial absorber is designed for THz imaging and EMI shielding. A unique oval-shaped structure with three circular ring-shaped resonators is proposed with a unit cell dimension of36×36×19.6μm3. The absorbance of the proposed multiband MMA is 98.57%, 90%and 99.85% at 5.58, 7.98-8.84, 11.45THz frequency respectively. Return loss is nearly the same for the changing incident and polarization angle. Therefore, this metamaterial absorber with a wide range of polarization insensitivity is found and it is also suitable for quantum RADAR Imaging, energy harvesting, and optoelectronic devices.

Optical Brewster Metasurfaces Exhibiting Ultrabroadband Reflectionless Absorption and Extreme Angular Asymmetry

Ultrabroadband reflectionless absorption of light is in great demand for many applications. This study proposes a type of nonresonant, impedance-matched optical metasurface that exhibits ultrabroadband reflectionless absorption, based on the anomalous Brewster effect. Extremely asymmetric behavior---a transition from perfect transparency to perfect absorption---appears when the sign of the angle of incidence changes, due to the coexistence of the traditional and anomalous Brewster effects. Such high-efficiency metasurfaces may find application in optoelectronic and thermal devices such as photovoltaics, photodetectors, and thermal emitters.

Expanding of Excimer Laser Photoablation’s Functionality in Ophthalmology

One of the significant weaknesses of excimer laser-based vision correction devices is the difficulty of achieving a required change in the refractive properties of the cornea to sharply focus the image on the retina with distance from the working area (ablation zone) center to the periphery due to a change in the laser beam incidence angle. The study is aimed at improving the quality of laser action on the eye cornea by introducing an optical corrective system into the existing excimer laser vision correction equipment, ensuring the coincidence of the direction of the laser beam incidence on the corneal surface with the normal.It has been shown that the greater the reflection coefficient, the lower the absorbed energy, and the shallower the laser radiation penetration and ablation depths, which reduces the laser action opportunities and quality. When using excimer laser vision correction devices, it has been proposed to change the angle of the laser beam incidence on the cornea with a distance from the working area (ablation zone) center to the periphery during the surgery by introducing an optical corrective system based on a lightweight controllable and movable mirror, which allows achieving the coincidence of the direction of the laser beam incidence on the corneal surface with the normal.The studies have shown that the coincidence of the laser beam incidence on the corneal surface at any point with the normal when using a priori data on the specifics of the patient's eye allows expanding the functional opportunities of excimer laser photoablation, i. e., expand the ablation zone by 30 % and eliminate the possibility of errors caused by the human factor. The technique proposed can be used for excimer laser vision correction according to PRK, LASIK, Femto-LASIK, and other methods. To implement this approach, a patented excimer laser vision correction unit has been proposed with a PCcontrolled optical shaping system comprising galvo motor platforms and galvo mirrors installed on them.

Resonance tuning for dynamic Huygens metasurfaces

Metasurfaces with dynamic optical performance have the potential to enable a broad range of applications. We computationally investigate the potential of dielectric Huygens metasurfaces, supporting both electric and magnetic dipole resonances, as a candidate platform for dynamic tuning. The asymmetric response of the two dipole resonances to changes in geometric and material parameters, and the potential for separate control of amplitude and phase, is analyzed. A review of dynamic materials, and their promise and limitations for use in dynamic Huygens metasurfaces, is discussed. Vanadium dioxide ( V O 2 ) is recognized as a singularly interesting material, due to its variable refractive index and optical absorption in response to several stimuli. Transmitted phase modulation of ± π is computationally demonstrated as a function of decaying resonance utilizing only the first 5% of the insulator-metal transition, corresponding to a temperature change of < 10 ∘ C . As another case study utilizing asymmetric resonance tuning in response to changing incidence angle, phase modulation ( 2 π range for reflected light and > --> 1.5 π for transmitted light) and amplitude modulation (from R = 1 to T = 1 ) are demonstrated using a simple silicon metasurface with varying incident angle within a range of ∼ 15 ∘ on two axes. A promising implementation within a micro-electromechanical system (MEMS)-based spatial light modulator, similar to conventional digital micromirror devices, is discussed.

Aluminium-Based Plasmonic Sensors in Ultraviolet.

We theoretically investigate the surface plasmon polaritons (SPPs) generated on an Al film covered by an Al2O3 layer in the context of their application as refractive index sensors. The calculated reflection spectra indicate SPP resonance excited by ultraviolet light, which was affected by the thickness of both the metal and the oxide layers on the surface. With optimized geometry, the system can work as a tunable sensor with a wide UV wavelength range 150–300 nm. We report a quality factor of up to 10 and a figure of merit on the order of 9, and these are comparable to the performance of more complicated UV plasmonic nanostructures and allow for the detection of a change of the refraction index. The sensor can operate on the basis of either the incidence angle or wavelength changes. The effect of oxide surface roughness is also investigated with an emphasis on amplitude-based refraction index sensing.

Polarization-insensitive broadband absorption enhancement with few-layer MoS2 film

A polarization-insensitive broadband absorber with few-layer molybdenum disulfide (MoS2) films is designed. The proposed absorber is composed of a dielectric antireflective coating and an ultrathin MoS2 film deposited on a metal square resonator array backed with a metallic mirror. It is shown that the polarization-insensitive absorption enhancement in the ultrathin MoS2 film is realized in the visible region for normally incident light. The distributions of electric field intensity at several resonant wavelengths are investigated to intuitively disclose the physical origin of such phenomenon. Moreover, the optical performances, i.e. the absorption spectra versus the change of incident angle for both polarizations, the angular sensitivity of the integrated absorption and the short-circuit current density, are simulated and examined, all of which outperforms the referenced planar structure. It is believed that the conclusions provide a promising way to design and fabricate ultrathin MoS2 solar cells and other novel optoelectronic devices.

Ultra wide-angle and broad-band metamaterial absorber based on magneto-electric dipole structure

An ultra wide-angle and broad-band magneto-electric dipole like metamaterial absorber (MEDMA) was proposed. The trapezoidal resistance films on the top layer and the upright resistance films in the middle are both equivalent to electric dipoles. The metal back plate together with the resistance films on the top layer are equivalent to magnetic dipoles. The radiation characteristics of magnetic dipole and electric dipole determine that the composite structure can achieve low back radiation effect and equal E-plane and H-plane patterns. According to reciprocity principle, the composite structure will also have a better absorption performance when it is used as an absorber. Simulation results show that the absorption of the MEDMA is more than 90% under TM polarized waves of 3.4–8.0 GHz as the incident angle changes from 0° to 80°. For TE polarized waves of 3.2–9.0 GHz, the absorption with the incident angles of 0°–50° is more than 80%. The absorption performance for each part of the MEDMA was analyzed by the surface current distributions, and the impedance matching characteristics was demonstrated by Smith chart. This work may provide a technical way in stealth research.

Extraction and control of permittivity of hyperbolic metamaterials with optical nonlocality.

Metal nanorod arrays exhibit hyperbolic dispersion and optical nonlocality under certain conditions. Therefore, their optical behaviors can hardly be expressed by incident-angle-independent effective permittivity. Here we extract effective permittivity of silver nanorod arrays with diameters of 4 nm, 12 nm, and 20 nm by polarized transmission method in the visible range. The incident angles are chosen from 20° to 60° to study the influence of optical nonlocality on permittivity. We demonstrate how the diameter of the nanorods can control the effective permittivity beyond the effective medium theory. The results suggest that the effective permittivity gradually loses its accuracy as the diameter increases due to the optical nonlocality. Our experiment verifies that ultrathin nanorod arrays can resist the fluctuations caused by changes in incident angle. We also extract k-dependent effective permittivity of nanorods with larger diameters.

E. Coli detection using surface plasmon resonance

The high sensitivity of chalcogenide surface plasmon resonance (SPR) structures with chalcogenide films is fructified to elaborate the salinity sensor for the seawater. A four layers configuration was taken into consideration, comprising a BK7 prism, a gold thin film, a chalcogenide As2S3 film and the ambient medium, which is the β-Galactosidase solution. The transfer matrix formalism was used in our study to determine the reflectances characterizing the plasmonic structure. The two polarization modes (TE and TM) were taken into consideration, in order to determine the best configuration that allows an optimal sensitivity. The structure used as optical sensor has a high sensitivity. A 0.05 % change in concentration causes an 18-arc seconds change in plasmonic resonance incident angle and it can be resolved.