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Design and analysis of multi-hexagonal reversible encoder using photonic crystals
摘要： In this paper, a 4 × 2 reversible encoder with hexagonal lattice has been designed using two-dimensional photonic crystals with non-linear refractive index. In order to demonstrate the working of the encoder, we have used the multi-hexagonal shaped structure arranged in parallel with appropriate inclination to get the desired output. During its functionality as an encoder, more than 98% of the power is coupled at the output port to obtain logic 1 and less than 17.2% of the power is coupled for obtaining logic 0. In addition, during its functionality as a reversible encoder, the logic 1 and logic 0 correspond to 97.5% and 15.1%, respectively. The proposed encoder provides an improved contrast ratio of 12.18? dB and 11.5?dB for logical states of 01 and 10, respectively.
关键词： Photonic integrated circuits,Optical reversible encoder,Photonic crystal,Photonic band gap
更新于2025-09-23 15:21:21
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Thermal darkening of one-dimensional photonic crystal containing tellurium suboxide
摘要： The purpose of this study is to experimentally and theoretically evaluate the optical properties of a one-dimensional photonic crystal (PC) with a defect layer before and after an annealing procedure. A sputtering technique with high index (TeOx) and low index (SiO2) materials was used to fabricate the 1D PC with a defect layer. The chemical and structural analysis of a single layer TeOx thin film was evaluated by X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), and X-Ray Diffraction (XRD). The optical constant of the single layer was also determined based on the envelope method from transmittance spectra measured by ultraviolet visible near-infrared spectrophotometry (UV-VIS-NIR). The measured reflectance spectra of the 1D PC were compared with the results simulated using the transfer matrix method (TMM) before and after the annealing procedure. A photonic bandgap (PBG) appears within the desired, near-infrared (NIR), region. The defect mode in the 1D PC was observed at λ = 1455 nm within the PBG of λ = 1235–1723 nm (Δλ = 488 nm). The reflectance spectra overall shifted toward longer wavelength due to thermal darkening effect resulting from the thermally induced optical property changes.
关键词： Photonic band gap,One-dimensional photonic crystals,Tellurium suboxide,Thermal darkening,Defect layer
更新于2025-09-23 15:21:01
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The Optical Properties of Metamaterial-Superconductor Photonic Band Gap With/Without Defect Layer
摘要： In the present work, we have investigated theoretically the optical properties of a new one-dimensional defected photonic crystal structure (1DDPC). The structure is composed of alternating layers of metamaterial (double-negative material) and high Tc superconductor material called Hg1223 defected with a dielectric material (SiO2) at the center of the structure. The transmittance spectra of the proposed structure are obtained by using the transfer matrix method (TMM). We noticed that multiple transmittance peaks within the photonic band gap (PBG) as the thickness of defect layer increases. The tunable filtering feature is obtained by varying the thicknesses of metamaterial and superconductor layer. In addition, the defect peak is red shifted as well as photonic band gap tuned to low-frequency region. Our structure is sensitive to the variation of the angle incidence. Also, defect mode shown to be blue shifted as the angle of incidence increases. The tunable filtering properties are very useful in the optoelectronic applications.
关键词： Metamaterial,Photonic band gap,TMM,Superconductor
更新于2025-09-23 15:21:01
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Optical resonance near the edge of a photonic band gap (PBG): turning the effects of a PBG on/off using a resonant driving field
摘要： We studied the effects of a coherent monochromatic resonant laser field driving the transition of a two-level atom embedded in a photonic band gap (PBG) material on the emission dynamics of the atom. When the transition frequency of the atom lies outside a PBG and sufficiently far from the band edge that the emission dynamics of the atom is not normally affected by the gap, the dynamic stark splitting of the upper level of the atom into two dressed states by a sufficiently strong resonant driving field can bring the lower dressed state close enough to the band edge or even inside the gap so as to be affected by the gap, providing a switchable means of extending the novel effects of atom–photon interaction near the edge of a PBG for atomic transitions outside the gap and far from the band edge. The net effect is as if a sufficiently strong resonant field driving a transition of an atom embedded in a PBG actively shifts the PBG close enough to the transition so that the gap affects the emission dynamics associated with the transition.
关键词： Photonic band gap,dynamic Stark splitting,optical resonance
更新于2025-09-19 17:15:36
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Electrically Tunable Liquid-Crystala??Polymer Composite Laser with Symmetric Sandwich Structure
摘要： This study investigates and develops for the first time an electrically tunable liquid-crystal?polymer composite laser with a symmetric sandwich structure. This structure includes two identical polymer-stablized cholesteric liquid-crystal (PSCLC) layers, and a dye-doped nematic LC (DDNLC) layer is sandwiched between them. The PSCLC and DDNLC layers act as distributed Bragg reflectors and half-wave plate with a gain medium, respectively. The entire cell behaves as an optical cavity, where the resonant modes occur at the maxima of the cell’s transmission spectrum. Through the competition among the resonant modes by considering the gain and loss, the resonant mode with the lowest lasing threshold can be sieved out for lasing occurrence. When the same voltage is applied to the two PSCLC layers, the pitch gradients are simultaneously formed through the two layers because of the electrically induced ion-concentration gradients. When the voltage increases, the pitch gradients increase, thereby leading to the expansion of the cell photonic band gap (PBG) and blue shift of the lasing wavelength. The sandwich cell PBG can expand from 55 nm to over 170 nm, and the tuning range of the lasing wavelength is as high as 70 nm, which is the widest ever achieved in LC-related sandwich systems. The proposed configuration of the sandwich sample presents new insights into tunable LC PBG and laser devices, thereby providing potential applications in the form of sensors, medical imaging, displays and lighting, among others.
关键词： distributed Bragg reflectors,electrically tunable,dye-doped nematic LC,photonic band gap,liquid-crystal?polymer composite laser,optical cavity,symmetric sandwich structure,half-wave plate,lasing wavelength,polymer-stablized cholesteric liquid-crystal
更新于2025-09-19 17:13:59
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Absorption Enhancement of a Thin Silicon Film with a 3D Photonic Band Gap Crystal Back Reflector
摘要： Currently, the efficiency of thin silicon film solar cells is constrained by a limited intrinsic absorption of silicon. The efficiency could be significantly increased by using a highly efficient back reflector that sends unabsorbed light back into the solar cell [1]. As an interesting candidate for a back reflector, we study here a thin 3D photonic band gap crystal [2, 3] that forbids light within the band gap for all directions and for all polarizations. We consider a dispersive complex refractive index obtained from experiments [4]. We find by extensive finite-element computations of the 3D time-harmonic Maxwell equations that even a very thin silicon 3D photonic band gap crystal slab reflects broadband visible light omnidirectionally for all polarizations. Our results show a nearly 2.6 times enhanced angle- and polarization-averaged absorption between 680 nm and 890 nm compared to a 2400 nm thin silicon film. We observe that a 3D inverse woodpile photonic crystal enhances the absorption of a thin silicon film by (i) behaving as a perfect reflector exhibiting nearly 100% reflectivity in the stop bands, and by (ii) generating guided resonant modes at many discrete wavelengths (as illustrated in Figs. 1(a, b)). We find that the absorption is enhanced by positioning an inverse woodpile back reflector at the back side of a thin silicon film, which will keep the length of the solar cell unchanged and also reduce the mass of the thin film solar cell. For a very thin sub-wavelength absorbing layer with a photonic crystal back reflector, as shown in Fig. 1(c), we identify two physical mechanisms that cause the large enhancement at discrete wavelengths: (i) a guided resonance due to the Bragg attenuation length of the photonic crystal [5] and (ii) confinement due to the effective surface defect on the photonic crystal.
关键词： back reflector,thin silicon film,absorption enhancement,3D photonic band gap crystal,solar cells
更新于2025-09-16 10:30:52
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Magneto-Optical Isolator Based on Ultra-Wideband Photonic Crystals Waveguide for 5G Communication System
摘要： This paper presents a novel magneto-optical isolator based on an ultra-wideband and high efficiency photonic crystals (PCs) waveguide and gyromagnetic ferrites. The three-dimensional numerical simulation finds that the photonic crystals waveguide’s (PCW) transmission efficiency rises with its height and width. The corresponding experiments are performed by using a triangular lattice Al2O3 dielectric posts array in 5G millimeter wave band. The measured transmission efficiency is up to 90.78% for the optimal PCs waveguide structure, which has ultra-wide operating bandwidth from 23.45 to 31.25 GHz. The magneto-optical isolator is designed by inserting two rectangular gyromagnetic ferrites into the PCs waveguide. Due to the contrast between the effective permeability of the left and right circular polarization waves passing through the magnetized ferrite sheets, the ferromagnetic resonance absorption of the forward and reverse waves is different. By using finite element method, the isolation is optimized to be 49.49 dB for the isolator and its relative bandwidth reaches 8.85%. The high isolation, broadband, and easy integration indicate that our designed magneto-optical isolator has significant advantage in 5G communication systems.
关键词： photonic crystals waveguides,magneto-photonic isolator,wideband,5G communication,photonic band gap
更新于2025-09-12 10:27:22
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All-Optical Ultra-Fast Graphene-Photonic Crystal Switch
摘要： In this paper, an all-optical photonic crystal-based switch containing a graphene resonant ring has been presented. The structure has been composed of 15 × 15 silicon rods for a fundamental lattice. Then, a resonant ring including 9 thick silicon rods and 24 graphene-SiO2 rods was placed between two waveguides. The thick rods with a radius of 0.41a in the form of a 3 × 3 lattice were placed at the center of the ring. Graphene-SiO2 rods with a radius of 0.2a were assumed around the thick rods. These rods were made of the graphene monolayers which were separated by SiO2 disks. The size of the structure was about 70 μm2 that was more compact than other works. Furthermore, the rise and fall times were obtained by 0.3 ps and 0.4 ps, respectively, which were less than other reports. Besides, the amount of the contrast ratio (the di?erence between the margin values for logics 1 and 0) for the proposed structure was calculated by about 82%. The correct switching operation, compactness, and ultra-fast response, as well as the high contrast ratio, make the presented switch for optical integrated circuits.
关键词： optical switch,photonic crystal,graphene,photonic band gap,kerr e?ect
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Optical Resonances in a 3D Superlattice of Photonic Band Gap Cavities
摘要： The confinement of light in three dimensions (3D) is an active research topic in Nanophotonics, since it allows for ultimate control over photons [1]. A powerful tool to this end is a 3D photonic band gap crystal with a tailored defect that acts as a cavity or even a waveguide [2]. When a one-dimensional array of cavities is coupled, an intricate waveguiding system appears, known as a CROW (coupled resonator optical waveguide) [3]. Remarkably, 3D superlattices of coupled cavities that resonate inside a 3D band gap have not been studied to date. Recently, theoretical work has predicted the occurrence of “Cartesian light”, wherein light propagates by hopping only in high symmetry directions in space [4]. This represents the optical analog of the Anderson model for spins or electrons that is relevant for neuromorphic computing and may lead to intricate lasing [5]. To experimentally study the propagation of light in a 3D superlattice of band gap cavities, we have fabricated 3D nanostructures from silicon by reactive ion etching (see Fig. 1). The photonic crystal has the cubic diamond-like inverse woodpile structure that is composed of two perpendicular sets of pores (in the X and Z directions) [6] and that reveals a broad 3D photonic band gap. By intentionally making two proximal perpendicular pores smaller, light is confined at their intersection, thus forming a cavity [7]. By fabricating two arrays of defect pores (see Fig. 1) we realize a 3D cavity superlattice. The challenge we address here is to experimentally identify resonances in this complex system. We measure reflectivity of the crystals with a large aperture (NA = 0.85) for both s and p-polarizations. With our setup we also record lateral scattered light, i.e., light that is input in the Z-direction, scattered, and detected in the X-direction. In presence of the intentional defects, we observe troughs in the stop band in reflectivity. The corresponding lateral scattering spectrum shows peaks in the stopband at the same frequencies as the reflectivity troughs, see Fig. 2. To distinguish cavity resonances from random speckle, we record several spectra at different locations on the crystal. Peaks reproducing at the same frequencies are attributed to light scattered from the cavity resonances. The appearance of the scattering peaks strongly depends on polarization in conformity with numerical calculations [7]. We now extend the numerical work to the range of pore sizes probed experimentally.
关键词： nanophotonics,Cartesian light,3D photonic band gap,cavity superlattice,coupled resonator optical waveguide
更新于2025-09-12 10:27:22
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[IEEE 2019 21st International Conference on Transparent Optical Networks (ICTON) - Angers, France (2019.7.9-2019.7.13)] 2019 21st International Conference on Transparent Optical Networks (ICTON) - Simulations of LED Patterned with IP-DIP Woodpile Structure
摘要： In this paper, we present simulations of three-dimensional (3D) photonic crystal structure (PhC) in IP-Dip polymer. We investigated woodpile structure and LED patterned by woodpile structure by various simulation methods. Structure was designed by the computer aided design (CAD) and optical properties were simulated by finite-difference time-domain (FDTD) and rigorous coupled-wave analyses (RCWA) simulation methods. We are focused on diffraction of optical radiation by woodpile structure and possibility of influencing extraction ratio and radiation patterns of LED with patterned woodpile structure. There is improving a significant percentage of transmittance of the radiation. It results in the influence of the radiation from the LED and it has positive impact on the LED parameters.
关键词： photonic crystal,simulations,3D woodpile structure,light extraction,photonic band gap,radiation pattern
更新于2025-09-11 14:15:04