Field In Waveguide Research Articles

Analysis of the Influence of Long-Wavelength Surface Waves on the Formation of the Wind-Wave-Scattered Acoustic Field in Oceanic Waveguides

The paper considers the interference structure during underwater pulsed sounding in the ocean associated with acoustic field diffraction by wind waves. When calculating the matrix of waveguide modes scattered by an agitated surface in oceanic waveguides, a two-scale surface wave model was used, in which the acoustic field is scattered by a resonance harmonic of waves, the phase velocity of which is modulated by larger waves. It is shown that when wind waves are undeveloped, i.e., the wave spectrum is nonisotropic and described by the JONSWAP model, the frequency matched filter response during observations of surface reverberations becomes asymmetric along the frequency axis and depends on the wind direction.

Numerical optimization design for waveguide bends with low-loss and wide-bandwidth in two-dimensional photonic crystal slabs

In this paper, we demonstrate some optimization designs for waveguide bends in two-dimensional photonic crystal slabs based on the effective index approximation. Four different types of waveguide bends with low-loss and wide-bandwidth are designed, which involve 60°, Z-shaped, Y-shaped and 120° waveguide bends in the two-dimensional triangular lattice photonic crystals. In all numerical experiments, the electromagnetic fields in the photonic crystal slab waveguides are solved by the finite element method in COMSOL software. Several strategies are applied to design slab waveguide bends with low-loss and wide-bandwidth, for example, adding some elliptical air-holes near the corner or adjusting the radii of some air-holes. For four optimized structures, the transmission efficiencies at 1550 nm are all more than 92%. As we show, this is achieved over a −0.915 dB bandwidth of more than 65 nm in all waveguide bends. The numerical results indicate that the design scheme we applied to optimize waveguide bends in photonic crystal slabs is simple and efficient, which can provide some useful guidance for further three-dimensional design.

Characterisation of spectroscopic and magneto-optical faraday rotation in Mn2+- doped CdS quantum dots in a silicate glass

We demonstrate the control of CdS and Mn2+-doped-CdS Q-dots in a silicate glass for magneto-optical applications. The microstructural properties of Q-dot glasses were investigated by X-Ray diffraction (XRD), Field Emission Transmission Electron Microscopy (FETEM) and the optical properties by UV–Visible–NIR and Photoluminescence (PL) spectroscopic techniques, respectively. The FETEM of the CdS QD–glass heat treated at 600oC reveals that the size of CdS and Mn2+-doped CdS Q-dots are in the range of 4-5 nm and 5-6 nm, respectively. The observed size distributions of Q-dots were in reasonable agreement with the data, derived from X-ray line broadening and estimated average Bohr radii using the UV–visible absorption data. Photoluminescence characteristics were investigated at room temperature by exciting the CdS and Mn2+-doped-CdS Q-dot glasses with a 420 nm excitation source, which yielded broad emission spectra in the visible and near-IR range (450-800 nm). We observed a red shift in the emission peak with increase in the Q-dot size, controlled by heat treatment temperature range (550-600oC). The room-temperature magneto-optical Faraday rotation measurements on Q-dots glasses were carried out using magnetic field strength up to 360 mT, and observed an increase in the value of Verdet constant, from 6.2 to 12.0°/T-cm, when comparing undoped CdS-Q-dot glass with Mn2+-doped CdS glass. The demonstration of enhanced Verdet constant in Q-dot silicate glasses with sub-Tesla field paves the path for engineering range magneto-optical devices for photonics, spintronics and sensors applications, in which the polarization of photons may be controlled with low-intensity magnetic field in optical waveguides.

Using the Belinfante momentum to retrieve the polarization state of light inside waveguides

Current day high speed optical communication systems employ photonic circuits using platforms such as silicon photonics. In these systems, the polarization state of light drifts due to effects such as polarization mode dispersion and nonlinear phenomena generated by photonic circuit building blocks. As the complexity, the number, and the variety of these building blocks grows, the demand increases for an in-situ polarization determination strategy. Here, we show that the transfer of the Belinfante momentum to particles in the evanescent field of waveguides depends in a non-trivial way on the polarization state of light within that waveguide. Surprisingly, we find that the maxima and minima of the lateral force are not produced with circularly polarized light, corresponding to the north and south poles of the Poincaré sphere. Instead, the maxima are shifted along the great circle of the sphere due to the phase differences between the scattered TE and TM components of light. This effect allows for an unambiguous reconstruction of the local polarization state of light inside a waveguide. Importantly, this technique depends on interaction with only the evanescent tails of the fields, allowing for a minimally invasive method to probe the polarization within a photonic chip.

Near-field imaging of inhomogeneities in a stratified ocean waveguide

In this work, we have derived the general representation of the scattered field in the three-layered ocean waveguide. Moreover, a generalized direct sampling method which does not rely on the equivalent condition of density, and a novel MUSIC method as an alternative approach, have been proposed for the reconstructions of penetrable obstacles in the stratified ocean waveguide. In practice, the methods are capable of recovering the scatterers of different shapes and locations, robust against noise, computationally fairly cheap and easy to carry out. We can consider them as simple and fast algorithms to supply satisfactory initial positions for the application of any existing more refined and precise but computationally more demanding techniques to achieve accurate reconstructions of physical features of objects.

Matched Field Processing in Phase Space

The traditional method of matched field processing is based on comparing the complex amplitudes of the measured and calculated sound fields in an underwater waveguide. Because of the high sensitivity of the wave field to variations in environmental parameters, the use of this approach requires accurate knowledge of the ocean-acoustic environment. In this paper, it is shown that under conditions of uncertain environment, instead of comparing the depth dependencies of complex field amplitudes, it is advisable to compare their field amplitude distributions in the phase plane “grazing angle-depth.” Such distributions are calculated using the coherent state expansion borrowed from quantum mechanics. Due to the absence of multipath in the phase space, the amplitudes of the coherent states are less sensitive to variations in the environmental parameters than the total wave field. This makes it possible to construct the similarity coefficients of measured and calculated fields that almost “do not notice” the differences of the compared fields caused by weak sound-speed variations, and “react” only to differences caused by strong changes in the sound-speed field and/or source position.

Tailoring of the self-assembled structures and optical waveguide behaviour of arylaminofluorenone derivatives

In this work, the fluorenone molecule was symmetrically difunctionalised in the 3,6-positions with four different arylamine moieties. Using slow evaporation, the four fluorenone derivatives (FO1-4) exhibit good ability to arrange into microstructures in the solid state. The electronic and steric effects of arylamine substituents influence both optical features and aggregation processes, as evidenced by photophysical and XRD characterization. SEM investigations have shown that the four FO1-4 derivatives arrange in four different microstructures. More specifically, the self-assembled 1D microribbon – shaped structure of FO1 exhibited an excellent optical loss coefficient (α) as low as 0.006 dBμm−1, suggesting a potential use of these materials in the field of optical waveguide.

Controlled interconversion of quantized spin wave modes via local magnetic fields

In the emerging field of magnonics, spin waves are considered for information processing and transmission at high frequencies. Towards this end, the manipulation of propagating spin waves in nanostructured waveguides for novel functionality has recently been attracting increasing focus of research. Excitations with uniform magnetic fields in such waveguides favors symmetric spin wave modes with odd quantization numbers. Interference between multiple odd spin wave modes leads to a periodic self-focusing effect of the propagating spin waves. Here we demonstrate, how antisymmetric spin wave modes with even quantization numbers can be induced by local magnetic fields in a well-controlled fashion. The resulting interference patterns are discussed within an analytical model and experimentally demonstrated using microfocused Brillouin light scattering ({\mu}-BLS).

Sense of Surface Plasmon Polarization Waveguide of Graphene

The honey structure of graphene is used in telecommunications, flexible displays, photonic devices, batteries, and electronic devices, where it achieves high heat dissipation efficiency. In order to obtain the high performances in the field of waveguide and sensor, we proposed a tunable plasmonic waveguide sensor based on periodic grating. The proposed device not only has the outstanding waveguide performance in gain threshold and propagation loss, which can reach 0.00745 dB/nm and 501 cm−1, respectively, but also the temperature sensitivity can achieve 0.28 nm/°C. The performances of waveguide and sensor can be tuned by changing the electronic characteristics of graphene, the structural parameters, and temperature, which indicate that the proposed device has considerable potential in ultra-speed plasma sensor devices, photonic integrated circuits, and tunable optical devices.

(INVITED) Methods for determining the refractive indices and thermo-optic coefficients of chalcogenide glasses at MIR wavelengths

Chalcogenide glasses have attracted much attention for the realization of photonic components owing to their outstanding optical properties in the mid-infrared (MIR) region. However, relatively few refractive index dispersion data are presently available for these glasses at MIR wavelengths. This paper presents a mini review of methods we have both used and developed to determine the refractive indices and thermo-optic coefficients of chalcogenide glasses at MIR wavelengths, and is supported by new results. The mini review should be useful to both new and established researchers in the chalcogenide glass field and fields of MIR optics, fiber-optics and waveguides. Three groups of methods are distinguished: (1) spectroscopic ellipsometry, (2) prism-based methods, and (3) methods using Fourier transform infrared (FTIR) transmission data. The mini review is supported by a brief discussion of refractive index models.

Design of the high-efficiency transmission-type polarization converter based on substrate-integrated waveguide (SIW) technology

In this paper, the design of a three-layer linear polarization converter based on substrate-integrated waveguide (SIW) technology is demonstrated. The transmission-type polarization converter with dual frequency polarization conversion characteristics is realized by a square-slot sandwiched by two layers of off-center dipole-slot resonator, and its asymmetric transmission (AT) property can be obtained by rotating the upper and the lower dipole-slot resonator to form an interlaced layout. An excellent polarization conversion ratio (PCR) can be realized by integrating the traditional transmission-type polarization converter with an SIW, and its physical mechanism can be explicated by guided wave field theory. Experimental results are presented and compared with the simulation results, and they demonstrated that ultra-high PCRs of the presented polarization converter are 0.87 and 0.99 for the measurement at the working frequency of 7.34 GHz and the simulation at the working frequency of 7.6 GHz, respectively. The designed polarization converter has greatly expanded the application field of SIW technology.

One-soliton shaping and inelastic collision between double solitons in the fifth-order variable-coefficient Sawada–Kotera equation

The main concern of the present article is to study the fifth-order variable-coefficient Sawada–Kotera (VcSK) equation which describes the motion of long waves in shallow water under the gravity. A single- and double-soliton rational solutions for this model are formally retrieved through the generalized unified method. For a single-soliton wave, the velocity, the amplitude and the shape of the wave cannot be affected by variable coefficients. There is an inelastic collision (the collision that makes change in amplitude of the soliton waves and shifts in their trajectories) between the double-soliton waves due to the time-varying field in a graded-index waveguide. It hoped that the established solutions can be used to enrich the dynamic behaviors of the VcSK equation.

Electric Field and Dispersion Characteristic Calculations of Glass Tube Waveguides Filled with Biological Substances

This study presents calculation of dispersion characteristics in the frequency range 1–100 GHz as well as electric field distributions in an open cylindrical waveguide with a central channel. The waveguide is made of glass material. The channel can be either empty or filled with blood plasma or blood cells. We investigated two kinds of electromagnetic (ЕМ) waves, the “tube” and “core” modes, each having a different structure of their electric fields. In the current study, the analysis focused on the fundamental and the first higher hybrid magnetic and electric “tube” modes. The fundamental “tube” mode that propagates in the waveguide filled with blood plasma is characterized by a very small loss at frequencies above 65 GHz. Meanwhile, the first higher mode suffers from strong attenuation in the same frequency range. This calls for finding ways to improve the waveguide’s broad-bandwidth. Our approach involves determining the dependence of this parameter on the inner radius of the waveguide. Extremes of the waveguide’s broad-bandwidth are observed at certain values of its inner radius. When the waveguide is filled with blood plasma or blood cells, the electric fields of the magnetic “tube” mode concentrate around the channel, and the electric field intensity decreases with the propagation of this mode along the waveguide, i.e., with increase of coordinate z. If the channel is filled with blood cells, the electric field of the hybrid magnetic “core” mode is concentrated in the center of the waveguide. This mode is characterized by a large attenuation h”, which reaches 500 m−1 at 30 GHz.

Methods for including uncertainty in modeling and simulation of acoustic propagation in ocean waveguides

Two main classes of uncertainty are associated with modeling and simulation of acoustic fields in ocean waveguides. These classes, generally known as aleatory and epistemic uncertainties, represent opposite ends of a spectrum of possible types of imperfect knowledge concerning the system. Aleatory uncertainty can be interpreted physically as natural ocean variability which is typically characterized by probability density functions, provided sufficient information is available to justify their specification. On the other hand, epistemic uncertainty is associated with incomplete scientific knowledge concerning some aspect(s) of the system under analysis. While epistemic uncertainty can be reduced by the inclusion of additional information, e.g., data refinements, acquisition of additional data or more realistic modeling of the system, aleatory uncertainty cannot be eliminated or reduced because it is judged by the modeler to be inherent in the structure of the system. Both types of uncertainty are discussed, with an emphasis on the aleatory contribution based on stochastic basis expansions. Tradeoffs with Monte-Carlo and Bayesian methods are also considered. When density functions are not available, weaker inferential estimates based on epistemic approaches are appropriate and a hybrid aleatory-epistemic framework is outlined for treating these situations. [Work supported by the Office of Naval Research.]

Gyroton with the Corrugated Resonator

A new type of high-power electronic device—a gyroton with a corrugated resonator—is described and investigated. Spatial bunching of the electron beam does not occur in this device, however, highly efficient electron beam power conversion into the rotating electromagnetic field power is possible. The rectilinear electron beam deviates from the axis by the slow TM11 wave, then it gives up longitudinal energy to the same wave with more than 78% efficiency, and an output power up to 30 MW. The developed mathematical model of the interaction of the relativistic electron beam with an irregular circular waveguide and resonator fields presented in this article can be used to calculate and optimize the processes occurring in various microwave electronic devices, such as gyrotrons, gyrotons, TWT, Gyro-TWT, and BWT.

Simulation and analysis on low-frequency scattering characteristics of the finite cylindrical shell in shallow water

Low-frequency acoustic scatterings from a finite cylindrical shell are numerically analyzed by FEM. The simulation results show that the acoustic-scattering field in waveguide has lots of frequency-related sidelobes, while no sidelobes exist in free space at low frequencies. The simulation also indicates that the module value in waveguide can be almost 20 dB larger than that in free space at low frequency, which is caused by the ocean boundaries. We also demonstrate that when the incident wave direction is normal to the target at low frequency, the target strength will be maximum and the distribution of the acoustic-scattering field is axisymmetric about the incident waving direction. Meanwhile, the acoustic-scattering field is also related to the impedance of the seabed, and the change of the impedance makes just a little contribution to the scattering field. Finally, the influence of different target locations is analyzed, including the targets near the sea surface, seabed and the middle region of the ocean waveguide, respectively. From simulation results, it is evident that the distribution of the acoustic-scattering field at low frequency has a little difference, which is smaller than 0.5 dB with various target locations, and the change is frequency and boundary-related.

MODELING OF THE ELECTROMAGNETIC FIELD OF A RECTANGULAR WAVEGUIDE WITH SIDE HOLES

MODELING OF THE ELECTROMAGNETIC FIELD OF A RECTANGULAR WAVEGUIDE WITH SIDE HOLES

Ultracompact Optical Hybrid Based on Standing Wave Integrated With Graphene-Based Photodetector for Coherent Detection

In this paper, we propose a novel scheme to integrate an optical hybrid based on standing wave with graphene photodetector (GPD). Different from optical hybrids ba-sed on multimode interference (MMI) couplers, the proposed optical hybrid can be miniaturized by constructing a standing wave field in a silicon strip waveguide. The waveguide-integrated GPD with symmetric electrodes is adopted as an ultrafast self-differential photodetector (SDPD), instead of conventional balanced-photodetectors (BPDs) based on p-i-n photodiodes in a coherent receiver. By placing two sysmmetric interdigitated electrodes of the SDPD at nodes and antinodes of the standing wave, it is convenient to realize the integration of the proposed optical hybrid with the graphene-based SDPD, which can effectively reduce the complexity of a coherent receiver and meet the future demand for wide bandwidth. The finite-difference time-domain method was used to calculate optical absorption for demonstrating operation feasibility. Finally, device bandwidth and effective responsivity have been discussed. In theory, our scheme would provide a feasible way to realize a high-speed compact coherent receiver.

All-Optical NOT Gate Based on Nanoring Silver-Air Plasmonic Waveguide

In this work, all-optical plasmonic NOT logic gate was proposed by using metal-insulator-metal (MIM) plasmonic waveguides design. This logic gate is numerically analyzed by COMSOL Multiphysics 5.3a. Recently, plasmonics have attracted more attention due to its huge applications in all optical signal processing. Due to it’s highly localization to metallic surfaces, surface plasmon (SP) may have many applications in sub wavelength to guide the optical signal in waveguides to overcome the diffraction limit which considered a big problem in conventional optics. The proposed design of MIM structure is consist of a dielectric waveguides plus metallic claddings, which guide the incident light strongly in the insulator region. Strong localization and relatively simple fabrication make the MIM waveguides the potential key design of Nano-scale all optical devices. Our design consists of symmetric ring structures with straight waveguides which based on MIM structure. All-optical logic gate (NOT gate) behavior is achieved from utilizing the interface between straight waveguides and ring structure waveguides. By switching the activation of the control port, the propagation of the outgoing field in the output waveguide will be changed. As the simulation results show, the proposed structure could operate as an all-optical NOT logic gate. This gate would be a potential component in many applications of all-optical signals processing.

Recent Advances of the Polymer Micro/Nanofiber Fluorescence Waveguide.

Subwavelength optical micro/nanofibers have several advantages, such as compact optical wave field and large specific surface area, which make them widely used as basic building blocks in the field of micro-nano optical waveguide and photonic devices. Among them, polymer micro/nanofibers are among the first choices for constructing micro-nano photonic components and miniaturized integrated optical paths, as they have good mechanical properties and tunable photonic properties. At the same time, the structures of polymer chains, aggregated structures, and artificial microstructures all have unique effects on photons. These waveguided micro/nanofibers can be made up of not only luminescent conjugated polymers, but also nonluminous matrix polymers doped with luminescent dyes (organic and inorganic luminescent particles, etc.) due to the outstanding compatibility of polymers. This paper summarizes the recent progress of the light-propagated mechanism, novel design, controllable fabrication, optical modulation, high performance, and wide applications of the polymer micro/nanofiber fluorescence waveguide. The focus is on the methods for simplifying the preparation process and modulating the waveguided photon parameters. In addition, developing new polymer materials for optical transmission and improving transmission efficiency is discussed in detail. It is proposed that the multifunctional heterojunctions based on the arrangement and combination of polymer-waveguided micro/nanofibers would be an important trend toward the construction of more novel and complex photonic devices. It is of great significance to study and optimize the optical waveguide and photonic components of polymer micro/nanofibers for the development of intelligent optical chips and miniaturized integrated optical circuits.