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Two dimensional (2D) Photonic crystals (PhCs) based cross waveguide structure (CWs) consisting of resonant cavity is investigated in this paper. Investigations are done using Two Dimensional Finite Difference Time Domain (2DFDTD) method. Transmission characteristics have been obtained for different radii of central rod placed at crossing point of two waveguides and number of regular rods surrounding central rod. Nonlinear behavior is also studied for different operating wavelengths.

Self-assembled opal crystals (bulk silica opals and PMMA thin opal films)have been studied by atomic force microscopy (AFM) and optical spec-troscopy. Reflectance and transmittance spectra (R(λ) and T (λ), respectively)as well as spectra of ellipsometric parameters Ψ(λ) and Δ(λ)demonstratepronounced changes with changing the angle of light incidence. Diameters ofspheres obtained from AFM-images correspond to those obtained from Braggfit to the diffraction resonance dispersions. The band of light losses detected byellipsometry at the spectral range of avoided band crossing of opal eigenmodeswas assigned to the energy exchange between these modes

Broadside radiation from Chern photonic topological insulators (PTIs) is studied in this work. The one-way dispersion of the topological edge mode is located in the fast wave region, making leaky-wave radiation possible. In this paper, design guidelines are presented and validated by full-wave simulations: the Berry curvature and the Chern number of photonic crystals are calculated to design a topological edge mode, then a leaky-wave antenna is proposed where a perturbation is utilized around the source location to eliminate open-stopband behavior and generate broadside radiation with high efficiency. It is demonstrated that leakage of the topological edge mode is capable of both frequency and bias scanning to generate a steerable beam across the broadside direction. Moreover, the mechanism behind the immunity of PTIs to defects is also investigated in detail. Although topological edge waves can bypass PEC-slab defects ideally, the phase change along the defect affects the radiation pattern. The switch between sum-difference beams by tuning the scale of the PEC-slab is direct evidence to verify our analysis. To sum up, the open-stopband behavior is overcome to realize broadside radiation, and the conditional robustness of PTIs in terms of antennas is clarified.

Since thin-film silicon solar cells have limited optical absorption, we explore the effect of a nanostructured back reflector to recycle the unabsorbed light. As a back reflector we investigate a 3D photonic band gap crystal made from silicon that is readily integrated with the thin films. We numerically obtain the optical properties by solving the 3D time-harmonic Maxwell equations using the finite-element method, and model silicon with experimentally determined optical constants. The absorption enhancement relevant for photovoltaics is obtained by weighting the absorption spectra with the AM 1.5 standard solar spectrum. We study thin films either thicker ($L_{Si} = 2400$ nm) or much thinner ($L_{Si} = 80$ nm) than the wavelength of light. At $L_{Si} = 2400$ nm, the 3D photonic band gap crystal enhances the spectrally averaged ($\lambda = 680$ nm to $880$ nm) silicon absorption by $2.22$x (s-pol.) to $2.45$x (p-pol.), which exceeds the enhancement of a perfect metal back reflector ($1.47$ to $1.56$x). The absorption is enhanced by the (i) broadband angle and polarization-independent reflectivity in the 3D photonic band gap, and (ii) the excitation of many guided modes in the film by the crystal's surface diffraction leading to enhanced path lengths. At $L_{Si} = 80$ nm, the photonic crystal back reflector yields a striking average absorption enhancement of $9.15$x, much more than $0.83$x for a perfect metal, which is due to a remarkable guided mode confined within the combined thickness of the thin film and the photonic crystal's Bragg attenuation length. The broad bandwidth of the 3D photonic band gap leads to the back reflector's Bragg attenuation length being much shorter than the silicon absorption length. Consequently, light is confined inside the thin film and the absorption enhancements are not due to the additional thickness of the photonic crystal back reflector., Comment: 23 pages, 15 figures

In this letter, a 180° ring-shaped hybrid based on the photonic crystal structure (PCS) is presented. The ring hybrid is designed for the operation wavelength of 1550 nm. Initially, a 180° hybrid is a design based on conventional microwave procedures. Different wave behavior inside the structure in THz and microwave frequency band has caused the wave propagation in this structure to change especially in terms of phase. By analyzing the field distribution within a structure, the rod arrangement is modified. In proposed structure, the phase difference between the output ports is greatly improved (about 90°). Also, by reducing the leakage and improving the matching, the output power of the ports tends to half power. Moreover, 32 nm wavelength shift is improved. The proposed structure’s reflectance value is less than 20 dB at the desired wavelength. The power splitting ratio between the two output ports is improved up to −3.7 dB and the power of the isolated port is less than −20 dB. This work has been analyzed using the FDTD method.

We have theoretically investigated the reflectance spectrums of the U-shape nanohole symmetry and asymmetric structure. It is shown that light can be perfectly confined in the photonic crystal slab at a given incident angle. Also, we studied the influence of U-shape nanohole size on reflectance spectrum and Q-factor of both at-Γ bound states in the continuum (BIC) and off-Γ BIC with the nanohole shape in symmetrical and asymmetrical cases. For a U-shape nanohole symmetry structure, it is shown that at-Γ BIC is dependent on the nanohole size. The Q-factor of the nanoholes structure at off-Γ BIC can reach the order of 106. The obtained results provide useful guidelines for practical implementations of biosensing, perfect filters and waveguides.

Based on the insights into the phenomenon of bound states in the continuum, a novel approach utilizing the momentum-space polarization morphologies of periodic structures to generate vortex beams (VBs) has been proposed. Such periodic structures modulate beams in a nonlocal way and require no precise alignment. However, the efficiency of such an approach has not been analyzed in detail, and the efficiency in previous realizations is far from optimized. Here, we analyze the factors affecting the efficiency of nonlocal VB generation. We show that the maximal efficiency cannot exceed 25% if the periodic structure carries only singlet resonances. To go beyond this limit, we propose two approaches to improve efficiency. We theoretically analyze the mechanisms and verify the approaches by full-wave simulations. Both of the approaches serve to improve the generation efficiency by several folds.

Chip-scale integrated light sources are a crucial component in a broad range of photonics applications. III-V semiconductor nanowire emitters have gained attention as a fascinating approach due to their superior material properties, extremely compact size, and capability to grow directly on lattice-mismatched substrates including silicon. However, their practical applications are still in the early stages due to the difficulties in achieving high-performance nanowire emitters and integrating nanowire emitters with photonic platforms. In this dissertation, we demonstrate III-V nanowire-based lasers monolithically integrated on silicon-on-insulator (SOI) platforms, which can be potentially employed for chip-scale optical communications and photonic integrated circuits. For this, selective-area epitaxy of InGaAs nanowires on 3D structured SOI platforms is developed by catalyst-free metal-organic chemical vapor deposition. Nanowires are precisely positioned on 3D structures, including waveguides and gratings, with nearly 100 % nanowire growth yield and wide bandgap tuning ranges. Next, nanowire array-based bottom-up photonic crystal cavities are demonstrated on SOI substrates. InGaAs/InGaP core/shell nanowire arrays form 1D and 2D photonic crystal cavities on SOI layers, and single-mode room-temperature lasing from these bottom-up cavities is achieved by optically pumping the nanowire arrays. We also show that the nanowire array lasers are effectively coupled with SOI waveguides, which is achieved by integrating bottom-up nanowires on pre-patterned SOI platforms. The lasing wavelengths of nanowire array lasers are in the ranges of 1,100–1,440 nm, which covers telecommunication wavelengths, all operating at room temperature. It is also shown that arrays of proposed lasers with individually tunable wavelengths can be integrated on a single chip by lithographically tuning the cavity geometries. In summary, the III-V nanowire lasers on silicon demonstrated in this dissertation represent a new platform for ultracompact and energy-efficient light sources for silicon photonics and unambiguously point the way toward practical and functional nanowire lasers.

Photonic band gap structure for the system of alternated layers filled with metamaterial and vacuum is studied. We assume that the metamaterial is the dispersive medium. We also assume that the permittivity and permeability have the identical expression. We use a single Lorentz term to describe them. For certain frequency interval, the metamaterial has the negative refractive index and behaves like a NIM. For other frequencies, it has the positive refractive index and behaves like a PIM. We compare the NIM case with the PIM case.

We developed a thermo-optically controlled nonmechanical optical beam scanner using a Si photonic crystal slow-light waveguide with a diffraction grating to achieve on-chip light detection and ranging (LIDAR). This Letter applies pre-emphasis signals to the thermo-optic control, and the cutoff frequency increases to 500 kHz. Observing the beam scanning in the space-time domain showed that the turn-on and turn-off times of the scanner for a rectangular drive voltage were 10 µs and reduced to 2.7 µs when the pre-emphasis signals were optimized. This new, to the best of our knowledge, result enables a frame rate of 29 fps for 12,800 resolution points in LIDAR.

This work presents the design and fabrication of a novel uniplanar microstrip patch antenna that is simultaneously dual-band and dual-polarized. By embedding a carefully designed metamaterial-based electromagnetic bandgap structure (MTM-EBG) into the edges of a conventional square patch, operation with orthogonal linear polarizations at both 3.6 and 5.8 GHz is achieved. The design is fully printed, compact, low-profile, and pin-fed using a shielded microstrip configuration, and it is 17% smaller than a conventional square patch at the lower operating frequency. The presented antenna shows a reflection coefficient better than −16 dB at each frequency and over 24 dB of port-to-port isolation. Radiation patterns are patch-like in both operating bands, with broadside gains of 6.4 and 5.3 dBi at the lower and higher operating frequencies, respectively. The antenna is fabricated using conventional PCB manufacturing methods, and measurement results are in very good agreement with simulations.

This day and age, blood pressure (BP) is one of the serious cardiovascular diseases. For the continuous monitoring of BP, a small, light weight and cuff less device is needed. A new photonic crystal based optical pressure sensor is designed for observing of blood pressure. Concept of developing photonic pressure sensor is based on surface sensing principle, when an exterior tension is applied on the outer face of sensor, it is spread evenly in the form of strain and vary the geometrical parameters of sensor hence the resonance wavelength is shifted and is sensed by the optical sensor. The sensor is designed through a 2D-ordered triangular lattice structure. To obtain very high-quality factor and good light confinement, quadruple hole resonant cavities with four scattering rods are introduced into the linear waveguide. The designed sensor can monitor pressure from 0 kPa or 0 mmHg to 50 kPa or 375 mmHg and its operating ranges lies between the optical C and S band. It has very high quality factor 1721, high sensitivity 25 µm/KPa and low minimum detectable pressure 3.98e-7 nN. Over all, the proposed approach provides a new sensing system for the human blood pressure monitoring which have high selectivity, low cost, light weight and easy to use. The band gap of the PCs structure has been computed by plane wave expansion (PWE) method. The transmitted power and resonant wavelength are calculated with the help of finite difference time domain (FDTD) algorithm.

In the present era due to miniaturization and integration of optoelectronic devices, it becomes important to design ultra-compact optical devices suitable for photonic integrated circuits (PICs). In this paper, new structure of a 2D photonic crystal-based Y-junction power splitter for TE polarization is proposed (wavelength of 1430 nm and size 10 × 10 µm2). Air holes are etched in the silicon substrate to form a hexagonal lattice structure for the Y- junction splitter. The optimization of the splitter is done by structural tuning at the bends and junction region. The structure is simulated by finite difference time domain (FDTD) and plane wave expansion (PWE) methods, which gives the normalized distribution of power and range of photonic bandgap (PBG), respectively. The simulated results confirm that a high transmission efficiency of 97.29% is achieved for night vision applications in the mid IR range. Moreover, the ultra-compact splitter is highly suitable for photonic integrated circuits.

In this article, the magnetized plasma in 1-D ternary periodic photonic crystals is utilized as a kind of single negative material whose real part of permittivity is negative. Some discrete resonant peaks with high transmittance can be observed in the transmission band due to the evanescent wave coupling between plasma layers and dielectric layers. The nonreciprocal effect can be achieved by injecting counter-propagating TM waves into the proposed structure whose time-reversal symmetry and space-reversal symmetry are broken. The transmission band of nonreciprocal evanescent waves can be modulated dynamically due to the tuning of the period number, the plasma frequency, the plasma cyclotron frequency, the filling factor of plasma, and the incident angle. The simulation results indicate that the proposed structure can achieve 100% transmission and strong nonreciprocity, which can supply multichannel unidirectional filters with theoretical references.

Surface waves such as plasmon, exciton, or phonon polaritons as well as guided modes supported by various planar structures attract particular attention due to their capability of capturing and carrying the optical signals in two- and one-dimensional systems. An important characteristic of such waves is their dispersion $$\omega ({{k}_{x}},{{k}_{y}})$$ , which can be designed on demand by nanostructuring of planar layered systems to obtain photonic crystal slabs and metasurfaces. Engineering the dispersion of surface waves gives rise to such exciting optical effects as transition from positive to negative refraction or from elliptic to hyperbolic dispersion, self-collimation, and diffraction-free propagation of surface waves. Along with the real part of the wave vector responsible for the phase of a propagating surface wave, a crucially important parameter for the applications is its propagation length that is related to the intrinsic losses of the mode. We propose an experimental approach allowing for the extraction of the full complex dispersion of optical surface waves and guided modes. The method relies on angle-resolved attenuated total internal reflection spectroscopy. In such a setup, scanning the air gap between the sample and a solid immersion lens yields controllable tuning of the coupling between the surface waves and the free space. In the experiment, we identify the regime of critical coupling of light to waveguide modes of a planar silicon slab and use it to extract their intrinsic losses and thus the propagation lengths in a broad spectral range. Our approach is a powerful tool for studies of light and hybrid light-matter surface waves of various kinds and may find its applications in the development of on-chip optoelectronic and nanophotonic devices.

A thermosensitive poly(N-isopropylacrylamide) (PNIPAM) circular gel film containing single-crystalline colloidal crystals was prepared, and the circular edge was pinched with washers to restrain the in-plane shrinkage of the gel film. Upon heating, the film shrunk in the thickness direction selectively, resulting in a change in the crystal structure of colloids embedded in the anisotropic shrunken gel. This led to the manipulation of the optical stop-band wavelength of the colloidal photonic crystals with a higher thermosensitivity and over a wider range of wavelengths covering a wide margin on either side of the visible-light region. The present method for enhancement of the sensitivity is very simple, and the principle should also be applicable to the gel-immobilized colloidal crystals that respond to stimuli other than temperature changes. The present findings contribute to the progress of practical applications of gel-immobilized colloidal photonic crystals as tunable photonic crystals and biological ...

We have demonstrated an effective approach to fabricating ultrathin lensed photonic crystal fibers (PCFs) with long working distances. The analytic function of the maximum working distance of lensed PCF has been first revealed, agreeing well with the numerical solutions. Our specific lensed PCF can be experimentally optimized in terms of the collapsed PCF length and fiber tip curvature by use of a graphite filament furnace. A maximum collimating working distance up to 4.84 mm for a lensed PCF with the diameter of 125 μm is demonstrated, which is more than four times as long as previous lensed PCFs. The ultrawide working bandwidth over 770 nm is also demonstrated. The significantly enhanced features in terms of key performance parameters such as working distances and bandwidth will accelerate a variety of applications using such ultrathin lensed PCFs.

High power and narrow vertical divergence lasers for the 980 nm wavelength range based on the photonic crystal (PC) structure are investigated. The structure of the PC layers and the position of the quantum well (QW) are optimized through mode analysis, which to maximize the output power of the PC laser. A broad area (BA) laser with $300~\mu $ m width and 4 mm cavity length yields 41.8 W output with far-field divergence angles of 16.5° in lateral and 16.8° in vertical at full width at half maximum (FWHM) under continuous-wave (CW) 48 A operating current at 5 °C.

In this paper, Two Dimensional Photonic Crystal (2DPC) based 4*2 and 8*3 encoders are devised using Y shaped waveguides. The proposed encoder operates at 1550 nm. In this attempt, initially, 4*2 encoder is designed and its corresponding structural parameters, such as, refractive index of the rod, radius of the rod and lattice constant, are optimized in order to attain better functional parameters. The primary functional parameters of the encoders are normalized power, contrast ratio, response time and bit rate. The Finite Difference Time Domain (FDTD) method and Plane Wave Expansion (PWE) method are utilized to analyze the performance parameters and Photonic Band Gap (PBG) of the encoder, respectively. As the proposed encoder is performing well, it is applicable for high speed optical integrated circuits.

Propagation of terahertz (THz) waves in silicon waveguides is of special interest for THz applications such as optical integrated circuits. In this paper, a photonic crystal-based rib silicon waveguide with a specific structure is designed for the first time which can be utilized for applications in THz region (including wavelength range of 30-35 μm). The dispersion curve and effective index are simulated over 30–35 μm for different rib heights. In addition, the dispersion coefficients up to the third order as well as the nonlinear parameter are calculated at the center wavelength of 33 μm from which the pulse evolution along the waveguide is simulated via solving the nonlinear Schrodinger equation (NLSE). The split-step Fourier (SSF) method is used to numerically solve the NLSE and then the pulse spectra at the input and output of the waveguide are simulated and compared to each other. Also, the effect of different parameters including rib height, pulse width, chirp and peak power on the THz pulse propagation is investigated. The results show that for lengths less than 1 cm, the pulse propagates almost without distortion, while for longer lengths, the shape and spectrum of the pulse are changed.

Interferometric scattering microscopy is increasingly employed in biomedical research owing to its extraordinary capability of detecting nano-objects individually through their intrinsic elastic scattering. To significantly improve the signal-to-noise ratio without increasing illumination intensity, we developed photonic resonator interferometric scattering microscopy (PRISM) in which a dielectric photonic crystal (PC) resonator is utilized as the sample substrate. The scattered light is amplified by the PC through resonant near-field enhancement, which then interferes with the, Here, the authors present photonic resonator interferometric scattering microscopy, which utilises a dielectric photonic crystal as the sample substrate. The resonant near-field enhancement leads to improved signal to noise ratio without increasing illumination intensity.

Optical beam scanning is a widely utilized function in optical systems and a compact nonmechanical solid-state device has long been anticipated. Here, we have studied such a device consisting of photonic crystal slow-light waveguides and switch trees, fabricated by a Si photonics process, employing a bespoke prism lens for beam collimation. Further in this study, we particularly demonstrated the operation of the device only by the thermo-optic (TO) tuning of its components, at a fixed wavelength of light. A spot beam of ∼0.1° divergence, was scanned in two dimensions, in the angular range of 40° × 8.8° and average power consumption of < 0.7 W. Neglecting some disordered beams caused by the non-uniformity of the fabricated device, the estimated number of resolution points was 400 × 32 = 12,800, which required a significant effort in the device fabrication and calibration, utilizing optical-phased arrays, if the same performance was targeted.

In this study, a sensor based on the located defect mode resonance is proposed, which can be used to simultaneously measure changes in magnetic induction intensity, plasma density, refractive index, and incident light angle. Plasma is introduced as the defect into a one-dimensional periodic structure, exciting the located defect mode resonance. The sensitivity, linear range, and figure of merit of the sensor are investigated using the transfer matrix method. The increase in the number of cycles can be used to improve the quality factor and FOM. We also consider the influence of the loss tangent on the sensor to a certain extent. The one-dimensional layered structure is utilized, which has the merits of small volume and simple manufacture. In addition, compared with the traditional sensors design, which focuses on the improvement of performance parameters, our proposed sensor concentrates on the study of multiple physical quantities. Therefore, we hope that our work can have some application potential in the field of measurement.

In this paper, a magnetophotonic crystal for enhanced absorption peak of one-way absorber is studied, in which two defect layers are introduced. The effects of magneto-optics and Tamm plasma polaritons are investigated. The optical properties of the novel photonic crystal with different periodic layer thicknesses and structures are shown in the wavelength range of 0.6–1.0 μm. Considering the large third-order nonlinearity and field localization, graphene is combined with the defect layer. Results showed that graphene can improve the absorption capacity of the absorber by 50%. Moreover, the influence of the relative position between graphene layer and magneto-optical layers on the absorption is further studied, which had found that this relative position can tune the absorption peak of the one-way absorber. Furthermore, the effect of incidence angle and the contour of electrical fields are also studied. Compared with the existing unidirectional devices, the structure has the advantages of small size, high efficiency, wide bandwidth and easy photoelectric integration. This work provides a new method for controllable perfect one-way absorber design in infrared wavelength range.

Recent years have witnessed significant exploration in photonic crystal (PC)-supported optical devices owing their competence in incorporation of optoelectronic components and miniaturization. Various structures of these devices have been explored in the literature with the aim to improve the performance. This paper compares two loop ring-resonators (horizontal and vertical arrangements) with hexagonal and rectangular lattice structures. Paper reports the outperformance of two loop PC ring-resonator for wavelengths of 0.85 μm, 1.3 μm and 1.55 μm, respectively, for hexagonal lattice-based two loop ring-resonator having vertical arrangement at width of 30 with Q-factor that are 22,500, 26,000 and 38,700 due to effective confinement of light and out-of-plane loss and propagation loss.

In this article, a structure based on one-dimensional photonic crystals that can be used for both angle sensing and refractive index sensing is proposed, which is achieved by optical Tamm state. Under Bragg scattering, its features are investigated by the transfer matrix method. This sensing structure is based on a multi-frequency absorption structure, which can achieve an absorption rate higher than 0.9 for three to four frequency points at the same time. The studied results demonstrate that the absorption peaks of such an absorption structure can be changed from three to four by adjusting the number of periods and silver layer thickness. Absorption peaks can occur red and blue shifts employing tailoring the thickness of defect and the angle of the incident light. By altering the thickness of the defect and the number of periods, the interval between the absorption peaks can be dominated. They are all with high-quality factors and can be used to bring about a high absorption sensor for the refractive index or angle. When it acts as a refractive index sensor, the operating range can cover from 2 to 2.7, whose sensitivity and average figure of merit are 32.3 THz/RIU and 100. If the presented device is used as an angle sensor, those values will become 0.5 THz/degree and 1.2, and its measuring range is from 25° to 70°. It can be said that the emergence of this special sensing structure will be possible to have a broad application prospect in the field of measurement.

Herein, we demonstrate a cavity-enhanced hyperspectral refractometric imaging using an all-dielectric photonic crystal slab (PhCS). Our approach takes advantage of the synergy between two mechanisms, surface-enhanced fluorescence (SEF) and refractometric sensing, both based on high-Q resonances in proximity of bound states in the continuum (BICs). The enhanced local optical field of the first resonance amplifies of 2 orders of magnitude the SEF emission of a probe dye. Simultaneously, hyperspectral refractometric sensing, based on Fano interference between second mode and fluorescence emission, is used for mapping the spatially variant refractive index produced by the specimen on the PhCS. The spectral matching between first resonance and input laser is modulated by the specimen local refractive index, and thanks to the calibrated dependence with the spectral shift of the Fano resonance, the cavity tuning is used to achieve an enhanced correlative refractometric map with a resolution of 10-5 RIU within femtoliter-scale sampling volumes. This is experimentally applied also on live prostate cancer cells grown on the PhCS, reconstructing enhanced surface refractive index images at the single-cell level. This dual mechanism of quasi-BIC spatially variant gain tracked by quasi-BIC refractometric sensing provides a correlative imaging platform that can find application in many fields for monitoring physical and biochemical processes, such as molecular interactions, chemical reactions, or surface cell analysis.

We propose a hole-assisted solid core Bragg fiber (SCBF) with a high-index-contrast cladding for near-infrared broadband single-polarization transmission in this article. The circular symmetry of a common SCBF is broken by the introduced air holes in the solid core for increasing the modal birefringence and polarization-dependent loss (PDL). In the proposed single-polarization SCBF, the confinement of guided modes predominantly depends on the photonic bandgap effect from the high-index-contrast cladding, and simultaneously rests with the total internal reflection from the interface between the solid core and air holes. The numerical results show that both the enhanced modal birefringence and PDL are strongly related to the refractive index, size and locations of air holes. We demonstrate that the modal birefringence for the fundamental mode can be up to the order of 10−3, and the difference in confinement losses between both polarized fundamental modes is no less than an order of magnitude, which is sufficiently large to support single-polarization operation. Moreover, the single-polarization bandwidth with the transmission loss lower than 0.1 dB/m is as high as 277 nm and the critical bend radius is as low as 1 cm, indicating the excellent performances of high bandwidth and bending resistance in the hole-assisted single-polarization SCBF.

In this paper, a new photonic crystal-based full-adder for the summation of three bits has been proposed. For realizing this device, three input waveguides are connected to the main waveguide. An optical power splitter is placed at the end of this waveguide. Concerning the amount of optical intensity inside this waveguide, two nonlinear resonant cavities transmit the waves toward the correct ports. When the cavities do not drop the optical waves, the splitter guides them toward the output ports. The maximum delay time of the presented structure is around 0.5 ps and shows the fastest response among the reported works. This improvement is obtained due to using the resonant cavities. The time analysis results in a maximum working frequency of 2 THz. Also, designing the structure in 93 µm2 demonstrates that it is more compact than the previous works. The normalized low and high margins are obtained around 10% and 85%, respectively. So, the proposed device is capable of considering optical processing circuits.

A photonic crystal based MOEMS pressure sensor design is presented in this work. The key design element is a circular diaphragm made of silicon (Si), integrated with a hexagonal ring resonator in the middle. The novelty of the work is the arrangement of the holes in the Si diaphragm in triangular orientation and optimization of sensitivity for pressure sensing. The pressure is applied at the center of the diaphragm which resulted in deformation, stress, and strain. The minimum observable deformation is 1.0073 nm and is at 6.3 µPa. The corresponding change in the refractive index is calculated for the stress applied. The resonant wavelength obtained for without load is 1.598 µm. The shift in the resonant wavelength for different loads are observed and tabulated. The modeling tool used to extract the mechanical parameters is ANSYS multiphysics. For 2D modeling and simulation of the ring resonator structure, MEEP is used for the implementation of FDTD. The Q-factor observed is 12,245 and sensitivity reported as 316.15 nm/RIU respectively.

Proposed work consist of simple and micro size optical MEMS based displacement sensor for detection of muscle movement in human body. Optical MEMS based structure, analyzed with rods-in air and hole-in slab configuration of photonic crystal. Remarkable shift in wavelength is observed in RIA configuration with high quality factor of 3245 compare to holes in slab in the photonic sensing structure with Q factor 1456. Optical sensitivity of device with rods in air configuration is 350 nm/RIU is obtained and from the result, the distinctly visible shift in wavelength is found to be optimum for fabrication of projected device. Proposed work is applicable for the muscle movement of human body during medical diagnosis and for daily life activities.

In this letter, ultra-fast pulse compression capacity of a triangular corrugated photonic crystal (PhC) was investigated through the finite difference time domain method. The group velocity dispers...

Three simple planar endfire antenna designs, in which surface-wave guides (SWGs) and a high-impedance surface (HIS) are used, are presented in this communication. These antennas support dual, triple, and quad surface-wave resonances, and exhibit wideband performance and high-gain potential. The HIS with a wide bandgap is used to prevent the propagation of the supported surface waves along a desired direction, and thus the endfire radiation tilted to the other direction is generated. The eigenvalue is adopted to explain that only TE0-mode surface waves are excited, and the characteristic mode analysis is presented to illustrate resonances of the tree antennas and explain why there are more resonances when the truncated number of the SWG increases. These antennas are fabricated and measured, and measured results validate the wideband and stable-gain performance.

Light can exert forces on objects, promising to propel a meter-scale lightsail to near the speed of light. The key to address many challenges in such an ambition hinges on the nanostructuring of li...

Structural color materials, which generate colors through the interaction between light and nano-microstructures, have always been research hotspots in the fields of display, anticounterfeiting and stimuli-responsive materials. Structural colors based on scattering have received increasing attention due to their wider viewing angles than that originating from the specular reflection of photonic crystals. However, the wide scattering spectrum of an amorphous structure leads to lower purity and brightness of the appeared colors. Few researchers have focused on the scattering of ordered structures due to their strong reflection and diffraction in the visible regions. In this work, by building ordered films (OFs) using SiO2 spheres (refractive index n = 1.46) with a diameter of 300–500 nm, for the first time, sharp scattering spectra with narrow full width at half-maximum (FWHM, 24 nm) were generated. Importantly, under ambient light, brilliant colors covering the entire visible region can be observed, and a formula was proposed to calculate the scattering spectra of OFs. Moreover, rainbow structural color was realized under irradiation of the nonparallel light, and full-spectrum structural color patterns were fabricated using building blocks with a single particle size by a spraying method. Finally, a composite structure was constructed to explore possibilities in the field of flexible transparent displays.

The dispersion properties of metamaterials and photonic crystals (PhCs) lead to an intensive research in the development of cavity resonators for the confinement of electromagnetic (e-m) radiation. In this work, we investigate the formation of Fabry–Pérot (FP) modes associated with hyperbolic-like dispersion (HLD) regimes in two-dimensional dielectric PhCs. Conventionally, FP modes are formed using an optical etalon, in which electromagnetic (e-m) waves reflecting from a partially reflecting mirror separated by a distance can interfere constructively and form a resonating mode. The FP mode observed in dielectric PhCs is formed due to the interference of cylindrical wavefronts inside the PhC interface at HLD frequencies. The FP modes in PhCs are surface localized, in which maxima/minima of the electric field lies along the air–PhC interface as a standing wave pattern and decays in air medium. Projected bandstructure, Eigen Frequency Contours (EFC), phase and group index calculations are carried out to explain the formation of FP modes in PhCs under different coupling cases. By varying the PhC dimension, FP modes with different spatial profiles are witnessed and the role of source position in exciting specific mode is demonstrated. The observed FP modes in PhCs are compared with the FP mode in an ideal indefinite slab. Based on the FP resonance in PhCs, a sensing device capable of detecting a bending angle less than $$0.05^\circ$$0.05∘ is demonstrated numerically. The FP modes in PhCs are scalable to other parts of e-m spectra so that the bending angle sensing can be extendable to terahertz and optical domains.

Based on the finite-difference-time-domain method and the plane-wave method, we study the imaging performance of two-dimensional hexagonal-structure photonic-crystal flat panel lens. First, the plane wave expansion method is used to verify that the structure has a negative refraction effect. The equivalent refractive index is – 1 when the normalized frequency is 0.251. The finite-difference-timedomain method is used to study the imaging performance of the structure for the small circular target (radius 1/12 wavelength). The simulation result shows that the imaging resolution of the target is greatly improved by a photonic-crystal flat lens with hexagonal structure. Then the side length of square air hole is changed to study the influence on the imaging performance. We find that the imaging resolution is different for different side lengths. The general trend is that the imaging resolution gradually increases, when the side length of hole increases (from 0.1 a to 0.5 a). There is an optimum resolution when the side length is 0.5 a. The result shows that the imaging performance of the lens can be optimized by changing the side length of holes. It provides a theoretical basis for the practical application of the photonic-crystal flat lens.

The paper describes the development of passive, chipless tags for a novel indoor self-localization system operating at high mm-wave frequencies. One tag concept is based on the low-Q fundamental mode of dielectric resonators (DR) which exhibits peak scattering at its resonance frequency. As the radar cross-section (RCS) of DRs at mm-wave frequencies is far too low for the intended application, arrays of DRs and combinations with dielectric lens and corner reflectors are investigated to boost the RCS while keeping the scattering retro-directive over wide-angle incidence. Satisfactory results are demonstrated experimentally in W-band with metal corner reflectors combined with planar arrays of DRs; the tags produce a high RCS level over a moderately broad angular range and a wide frequency range where they exhibit a notch at the resonance frequency of the dielectric resonators. These designs suffer from low coding range of 3 to 6 bit, degradations of RCS in angular range, and a difficult separation of the tag response from strong clutter. Both the suppression of large clutter interference by using time gating of the tag response and a larger coding range are promised by a chipless tag concept based on multiple high-Q resonators in photonic crystal (PhC) technology. Experimental samples are characterized as transmission resonators and as retro-directive tags at the 230 GHz band. As a concept to boost the retro-directive RCS with a truly wide-angle response, the integration of PhC resonators with a Luneburg lens is discussed.

The structure of an optical add-drop filter (ADF) which depends on a very-compact ring resonator made from a photonic crystal has been presented in the paper. An adequate structure of a three channel wavelength de-multiplexer along with a finite difference time domain is demonstrated in the visibility area. A 3D triangular lattice photonic crystal with 1.735 nm air pores in a silicon nitride planar waveguide provides a constraint for the light which can be detected. The double resonator has been simulated on a three-dimension photonic crystal and for the simulation of results, MATLAB has been used. The resultant structure consisting of three drops wavelengths at λ1 = 1555 nm, λ2 = 1579 nm, and λ3 = 1595 nm approximately. The average spacing between the adjacent channels is around 20 nm and the FSR obtained from numerical simulation is about 179 GHz. The output wavelength carries normalized transmissions of 0.97 having an inner rod radius for inner core 800. In addition to this, the Alternating Least Square—Add-Drop Filter (ADF)—Finite Difference Time Domain method has been used to achieve three various outputs such as transmitted intensity, reflectivity fineness, and constant factor. In future aspects, the simulation results can be further used in the fields of networks to design more accurate and efficient photonic crystals based on de-multiplexing devices.

In this paper we present the analysis of soliton propagation in photonic crystal metamaterials. Current analysis considers the case of the complex refractive index for double negative (DNG) materia...

Dirac dispersion cones enable remarkable wave phenomena in electronics as well as electromagnetic systems. In this work, the authors experimentally demonstrate for the first time the Dirac leaky wave antennas (DLWAs) at millimetre-wave (mm-wave) frequencies. The demonstrated DLWAs are implemented in the substrate integrated waveguide technology, delivering unprecedented features at high frequencies such as radiation at, and continuous beam scanning through broadside, with ease of fabrication, making these designs well suited for mm-wave applications such as emerging fifth generation and Internet of Things, radar and imaging. It is shown that a planar Dirac photonic crystal can be realised composed of air columns inside a host SIW waveguide, exhibiting a closed bandgap and linear dispersion around broadside. Phase and attenuation constants are controlled to obtain directive beam and scanning in a wide range of angles (from −30° to 20°). The presented DLWAs have a wide impedance bandwidth around 28 GHz with high efficiency, and operate with peak gains of about 16 dBi with