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A refractive index from negative to positive of graphene plasmonic crystal at the Dirac-like cone in mid-infrared region
摘要： In this work, two-dimensional plasmonic crystals composed of graphene nanodisks where the chemical potential varies in triangular symmetry are proposed. A special band structure of Dirac-like cone is obtained at the center of Brillouin zone in mid-infrared region. A refractive index of the plasmons from negative to positive is calculated by the method of eigen-fields averaging. Also, the isotropic distribution of the negative/positive effective permeability and permittivity is numerically demonstrated. In addition, the significant propagation characteristics including the reverse Snell’s law effect, deep-sub-wavelength focusing and negative Goos-H?nchen shifts are numerical simulated. The proposed structure may find broad applications in the fields of on-chip plasmonic interconnect, high density plasmonic integrated circuit techniques and nano-imaging in the future.
关键词： Plasmonic crystals,Graphene plasmon,Dirac-like cone,Negative refractive index
更新于2025-09-16 10:30:52
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Optimized Sensitivity Analysis of Phase Modulated Optical Fiber Sensor
摘要： the Influence of different oxide overlayers on performance of phase modulated optical fiber sensor coated with graphene is reported. The simulation model is constructed according to the the transmission matrix theory. In this work, we improve the phase sensitivity of the sensor by adding different oxides coatings include magnesium oxide (MgO), aluminum oxide (Al2O3), lutetium oxide (Lu2O3), scandium oxide (Sc2O3) and tellurium dioxide (TeO2) on the surface of monolayer graphene. The phase sensitivity of the sensor is optimized by the type and thickness of oxide coating. The phase sensitivity of the sensor with 35 nm TeO2 coating on the surface of monolayer graphene achieved 1.3467× 105deg/RIU.
关键词： phase modulated,refractive index,optical fiber sensor,D-type optic fiber,oxide
更新于2025-09-16 10:30:52
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Investigation of characteristics of waveguide channels system formed in PDLC with inhomogeneity of the amplitude-phase distribution of forming field
摘要： This work presents the results of modeling the influence of amplitude, phase and amplitude-phase heterogeneities of the forming field on the spatial distribution of the refractive index profile and, accordingly, the mode composition of radiation capable of propagating in waveguides formed by the holographic method in the photopolymer-liquid crystalline compositions. The spatial distribution of the refractive index is found by solving the system of kinetic equations. The mode composition of the radiation is determined by solving the dispersion equation for TE-modes.
关键词： holographic method,refractive index,waveguide channels,PDLC,mode composition
更新于2025-09-16 10:30:52
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Novel S-Bend Resonator Based on a Multi-Mode Waveguide with Mode Discrimination for a Refractive Index Sensor
摘要： In this paper, a multi-mode waveguide-based optical resonator is proposed for an integrated optical refractive index sensor. Conventional optical resonators have been studied for single-mode waveguide-based resonators to enhance the performance, but mass production is limited owing to the high fabrication costs of nano-scale structures. To overcome this problem, we designed an S-bend resonator based on a micro-scale multi-mode waveguide. In general, multi-mode waveguides cannot be utilized as optical resonators, because of a performance degradation resulting from modal dispersion and an output transmission with multi-peaks. Therefore, we exploited the mode discrimination phenomenon using the bending loss, and the resulting S-bend resonator yielded an output transmission without multi-peaks. This phenomenon is utilized to remove higher-order modes e?ciently using the di?erence in the e?ective refractive index between the higher-order and fundamental modes. As a result, the resonator achieved a Q-factor and sensitivity of 2.3 × 103 and 52 nm/RIU, respectively, using the variational ?nite-di?erence time-domain method. These results show that the multi-mode waveguide-based S-bend resonator with a wide line width can be utilized as a refractive index sensor.
关键词： multi-mode waveguide,integrated optical sensor,mode discrimination,refractive index sensor,S-bend resonator
更新于2025-09-16 10:30:52
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Plasmonic effects in the enclosed and opened metallodielectric bowtie nanostructures
摘要： Plasmonic effects in the enclosed and opened metallodielectric nanostructures, composed of a periodically bowtie-shape metal nanoparticles (MNPs), are numerically investigated and compared. The spreading range of resonance wavelength for the opened system is larger than that of the enclosed one due to more surface plasmon resonance (SPR) and hollow plasmon resonance (HPR) effects occurred in metallodielectric bowtie nanostructures. Numerical results exhibit that the sensitivity of the opened system could reach as high as 1056.60 nm/RIU. For the thinner shell thickness, it can fully support the high-energy mode with electric field concentration extended into the more dielectric core regions in the opened system, thereby provides higher sensitivity to local refractive index (RI) varies. In addition, the open hollow is accessible to the surrounding medium, and this makes it attractive for RI sensor and filtering applications. The highly sensitive optical performances give us a qualitative idea of the optical properties of SPR and HPR modes in the opened metallodielectric bowtie nanostructure system that can be as a promising candidate for analyzing the real nanocomposites and producing the nanomaterials with novel properties.
关键词： Hollow plasmon resonance,Surface plasmon resonance,Metallodielectric nanostructures,Refractive index sensor,Plasmonic effects
更新于2025-09-16 10:30:52
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Study of optical and structural properties of sputtered aluminum nitride films with controlled oxygen content to fabricate Distributed Bragg Reflectors for ultraviolet A
摘要： Aluminum nitride (AlN) films with controlled oxygen content were deposited on silicon substrates, and optical properties studied with dependency on film morphology. Combinations of argon (Ar) and nitrogen (N2) gases were used in RF magnetron sputtering of an AlN target. The resulting refractive index ranging from 1.6 to 2.0 at 400 nm was tuned by controlling the sputter gas flow rate ratio of Ar and N2. The resulting refractive index is associated with density and aluminum nitride content of the thin films. Distributed Bragg Reflectors (DBRs) optimized for ultraviolet-A reflectivity were fabricated with pairs of alternating AlN thin films using an explicit combination of low-n and high-n to further investigate the thin film optical properties. The effect of structural transformation in the DBR stack on the progress of optical properties was studied. The DBRs exhibit a negligible extinction coefficient, utilizing precise control of oxygen incorporation with one sputtering target.
关键词： Optical properties,Materials interface,Aluminum oxynitride,Aluminum nitride,AlN,Refractive index,DBR,Magnetron sputtering
更新于2025-09-16 10:30:52
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Oblique-Angle Deposited SiO <sub/>2</sub> /Al Omnidirectional Reflector for Enhancing the Performance of AlGaN-Based Ultraviolet Light-Emitting Diode
摘要： We report the improvement of the performance of AlGaN-based ultraviolet (UV)-light-emitting diodes (LEDs) using oblique-angle deposited SiO2-based omnidirectional reflectors (ODRs). The electron-beam (e-beam) deposition at angles of 60° and 80° resulted in the formation of porous SiO2 films. The refractive index (n) varied from 1.49 to 1.25 at 365 nm with changing angle from 0 to 80°. Simulation based on the transfer matrix method showed that the porous SiO2 (n = 1.25)/Al ODR gave the normal incidence reflectance of 95.4% at 365 nm, whereas the conventional SiO2 (n = 1.49)/Al and ITO/Al reflectors have the normal incidence reflectance of 93.8% and 79%, respectively. The UV-LED with different reflectors had a forward voltage in the range of 3.40–3.51 V at 20 mA. The UV-LEDs with porous SiO2/Al ODRs (40% mesh ohmic area) yielded 21% higher light output at 100 mA and 24% relative external quantum efficiency (EQE) at 6 mA compared with the one with a reference ITO/Al reflector. The plan-view emission images showed that the SiO2/Al ODR UV-LED displayed better current spreading than the reference one with the ITO/Al reflector experiencing current crowding near the p-pad.
关键词： refractive index,SiO2-based omnidirectional reflectors,AlGaN-based ultraviolet light-emitting diodes,external quantum efficiency,oblique-angle deposition
更新于2025-09-16 10:30:52
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Double-Track Waveguides inside Calcium Fluoride Crystals
摘要： Calcium Fluoride (CaF2) was selected owing to its cubic symmetry and excellent luminescence properties as a crystal of interest, and ultrafast laser inscription of in-bulk double-track waveguides was realized. The guiding properties of these waveguides in relation to the writing energy of the femtosecond pulse are presented. The modified double-track waveguides have been studied by systematic developments of beam propagation experiments and numerical simulations. Furthermore, an adapted model and concepts were engaged for the quantitative and qualitative characterization of the waveguides, particularly for the transmission loss measurements and the three-dimensional refractive index mappings of the modified zones. Additionally, polarization-dependent guiding was investigated.
关键词： Calcium Fluoride,quantitative phase imaging,waveguides,femtosecond lasers,cubic crystal,micro-processing,double-track,photonic device,direct laser writing (DLW),refractive index change
更新于2025-09-16 10:30:52
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High Refractive Index Inverse Vulcanized Polymers for Organic Photonic Crystals
摘要： Photonic technologies are nowadays dominated by highly performing inorganic structures that are commonly fabricated via lithography or epitaxial growths. Unfortunately, the fabrication of these systems is costly, time consuming, and does not allow for the growth of large photonic structures. All-polymer photonic crystals could overcome this limitation thanks to easy solubility and melt processing. On the other hand, macromolecules often do not offer a dielectric contrast large enough to approach the performances of their inorganic counterparts. In this work, we demonstrate a new approach to achieve high dielectric contrast distributed Bragg reflectors with a photonic band gap that is tunable in a very broad spectral region. A highly transparent medium was developed through a blend of a commercial polymer with a high refractive index inverse vulcanized polymer that is rich in sulfur, where the large polarizability of the S–S bond provides refractive index values that are unconceivable with common non-conjugated polymers. This approach paves the way to the recycling of sulfur byproducts for new high added-value nano-structures.
关键词： distributed Bragg reflectors,inverse vulcanization,refractive index,polymer photonic crystals
更新于2025-09-16 10:30:52
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Design and Characterization of Surface Relief Grating on Etched Multimode Optical Fiber For Refractive Index Sensing
摘要： We report a simple and compact optical fiber sensor based on surface relief gratings in conventional graded-index multimode optical fiber (GIMMF) for refractive index sensing. Bragg gratings on MMF are less explored compared to its single mode counterpart, even though the MMF platform possesses several advantages such as robustness, enhanced light-matter interaction and easy light coupling. In this work, surface relief gratings are directly written on one side of the cladding etched MMF core surface by using focused ion beam milling (FIB). A detailed theoretical analysis of the structure and sensing principle is analysed. The device performance as a refractive index sensor has been investigated experimentally by immersing the device in different concentration of NaCl solution. Experimental results show a sensitivity of 70 nm/RIU for a refractive index range of 1.333 to 1.345. The device is easy to fabricate with high repeatability and low cost, compactness in design and competent to be used in harsh environmental conditions. The surface grating on etched MMF provides a better interaction between the sensing region and the environment which makes it a potential candidate for various chemical and biological sensing applications.
关键词： optical fiber sensor,refractive index sensor,Multimode optical fiber grating,optical fiber micro-machining
更新于2025-09-16 10:30:52