Segmented Waveguide Research Articles

Ultra-broadband multimode fiber-to-chip edge coupler based on periodically segmented waveguides.

Mode-division multiplexing (MDM) technology demonstrates a bright outlook for enhancing the capacity of chip-scale or fiber-based optical communication. Nevertheless, the fiber-to-chip MDM optical interconnects are hindered by the considerable mode mismatch and inter-modal cross talk between the few-mode fiber (FMF) and on-chip few-mode waveguide (FMW). In this Letter, a new, to the best of our knowledge, multimode coupling solution based on periodically segmented waveguides for the MDM system is proposed, which achieves efficient conversion between LP01, LP11a, and LP11b modes in FMF and E11, E21, and E12 modes in FMW with low refractive index difference. The simulation results show that the coupling loss is less than 0.41, 0.27, and 0.90 dB for the three modes, over the wavelength range of 1100-1800 nm. The fabricated device based on a polymer platform shows low fiber-to-chip coupling losses of less than 1.8, 1.7, and 3.0 dB, respectively, over a 130 nm wavelength. The presented scheme provides a competitive solution for realizing the ultra-efficient integration of prospective fiber-chip optical interconnections and communications.

Steering sound propagation with Zeno barriers in acoustic waveguide arrays

In quantum systems, a counterintuitive phenomenon known as quantum Zeno dynamics is usually exploited to tailor and protect the coherent evolution of quantum states by the back action of quantum measurements and strong couplings. Here, with the quantum-classical analogy, we report that the acoustic Zeno dynamics can be reproduced in acoustic waveguide arrays by setting segmented waveguides. We experimentally demonstrate that the segmented waveguide acts as an acoustic barrier to tailor the whole Hilbert space into different subspaces by separating the communication between waveguides. By arranging the acoustic Zeno barriers, we can control the sound transport in waveguide arrays into the target output ports, such as the Zeno dynamics, analog-quantum walk, and analog-quantum logic gates. In this context, we highlight that the Zeno barrier can be a versatile tool to arbitrarily control and guide the sound transport in waveguide arrays, which can provide an alternative choice for acoustic metamaterials and metasurfaces without cumbersome and complicated structure design. The acoustic Zeno barrier may provide a versatile approach to manipulate acoustic wave propagation for designing advanced on-chip integrated sound devices.

An Erbium‐Doped Waveguide Amplifier on Thin Film Lithium Niobate with an Output Power Exceeding 100 mW

AbstractA high‐power thin film lithium niobate (TFLN) erbium‐doped waveguide amplifier (EDWA) is demonstrated with a maximum on‐chip output power of 113 mW and a gain of 16 dB. The on‐chip integrated EDWA is composed of large mode area (LMA) waveguide structures with a total length of 7 cm and a footprint of 1 × 1 cm2. Segmented LMA waveguides are connected with waveguide tapers to achieve on‐chip mode conversion, which maintains single‐mode propagation all over the EDWA even at the waveguide bends. The design leads to a significant increase in the amplified signal power by orders of magnitude and will open an avenue for applications such as on‐chip high‐power lasers and amplifier systems.

Electrically interfaced Brillouin-active waveguide for microwave photonic measurements

New strategies for converting signals between optical and microwave domains could play a pivotal role in advancing both classical and quantum technologies. Traditional approaches to optical-to-microwave transduction typically perturb or destroy the information encoded on intensity of the light field, eliminating the possibility for further processing or distribution of these signals. In this paper, we introduce an optical-to-microwave conversion method that allows for both detection and spectral analysis of microwave photonic signals without degradation of their information content. This functionality is demonstrated using an optomechanical waveguide integrated with a piezoelectric transducer. Efficient electromechanical and optomechanical coupling within this system permits bidirectional optical-to-microwave conversion with a quantum efficiency of up to −54.16 dB. Leveraging the preservation of the optical field envelope in intramodal Brillouin scattering, we demonstrate a multi-channel microwave photonic filter by transmitting an optical signal through a series of electro-optomechanical waveguide segments, each with distinct resonance frequencies. Such electro-optomechanical systems could offer flexible strategies for remote sensing, channelization, and spectrum analysis in microwave photonics.

Transverse Inscription of Silicon Waveguides by Picosecond Laser Pulses

AbstractIn this work, picosecond laser inscription of segmented waveguides in crystalline silicon based on a deterministic single‐pulse modification process is demonstrated. Pulses of 43 ps duration at 1.55 wavelength are used to transversely inscribe periodic structures with a pulse‐to‐pulse pitch of ≈2 . Infrared shadowgraphy images and Raman spectroscopy measurements indicate that the modifications exhibit a spherical shape. Characterization of waveguide performance at 1.55 for various pulse energies and periods is carried out. Direct comparison with numerical simulations confirms the presence of graded index waveguides, encompassing a micrometer core size and a maximum refractive index change of . This short‐pulse inscription approach can pave the way for 3D integrated photonic devices in the bulk of silicon.

Splitter-Based Sensors Realized via POFs Coupled by a Micro-Trench Filled with a Molecularly Imprinted Polymer

An optical–chemical sensor based on two modified plastic optical fibers (POFs) and a molecularly imprinted polymer (MIP) is realized and tested for the detection of 2-furaldehyde (2-FAL). The 2-FAL measurement is a scientific topic of great interest in different application fields, such as human health and life status monitoring in power transformers. The proposed sensor is realized by using two POFs as segmented waveguides (SW) coupled through a micro-trench milled between the fibers and then filled with a specific MIP for the 2-FAL detection. The experimental results show that the developed intensity-based sensor system is highly selective and sensitive to 2-FAL detection in aqueous solutions, with a limit of detection of about 0.04 mg L−1. The proposed sensing approach is simple and low-cost, and it shows performance comparable to that of plasmonic MIP-based sensors present in the literature for 2-FAL detection.

Defect mode properties of an acoustic structure made up of periodic expansion chambers containing defects

Noise pollution is an environmental menace in agricultural, industrial, commercial, and residential facilities of all countries around the globe particularly developing countries. This paper examines noise reduction of an acoustic band gap structure made from expansion chambers. The interface response predictions of the transmission loss are presented and compared with the experiment, and the boundary element method (BEM) data obtained from the literature showing good agreement at low frequencies. A wider band gap with and stronger muffling effects at a lower frequencies is shown, which depends on the geometry of the expansion chamber and the periodicity. Furthermore, the periodicity is broken by the introduction of defects to analyse the narrow frequency transmission bands within the band gaps. In this work, the defect is artificially produced and controlled by the length and/or the cross-section of the central waveguide segment. The influence of dimension parameters on the wave suppression band gaps is analyzed. We show that the defect mode transmission moves within band gaps. It location can be controlled by the dimension of the defective expansion chamber. The closest to the middle of the band gap, the narrowest becomes. The results presented in this work can help to guide the achievement of broader acoustic band gaps in waveguide systems.

Singular optical propagation properties of two types of one-dimensional anti- PT -symmetric periodic ring optical waveguide networks

Two types of one-dimensional (1D) anti- PT -symmetric periodic ring optical waveguide networks, consisting of gain and loss materials, are constructed. The singular optical propagation properties of these networks are investigated. The results show that the system composed of gain materials exhibits characteristics of ultra-strong transmission and bidirectional reflection. Conversely, the system composed of loss materials demonstrates equal transmittance and reflectance at some frequencies. In both the systems, a new type of total reflection phenomenon is observed. When the imaginary part of the refractive indices of waveguide segments is smaller than 10−5, the system shows bidirectional transparency with the transmittance tending to be 1 and reflectivity to be smaller than 10−8 at some bands. When the refractive indices of the waveguide segments are real, the system will be bidirectional transparent at the full band. These findings may deepen the understanding of anti- PT -symmetric optical systems and optical waveguide networks, and possess potential applications in efficient optical energy storage, ultra-sensitive optical filters, ultra-sensitive all-optical switches, integrated optical chips, stealth physics, and so on.

Silicon Subwavelength Grating Slot Waveguide based Optical Sensor for Label Free Detection of Fluoride Ion in Water

Recently, Subwavelength Grating Waveguides (SWG WG) attract a lot of attention for sensing applications because it offers better sensitivity than conventional WGs. The sensitivity of SWG WG is greatly improved due to the interaction between the analyte and guiding mode in the SWG segments. In this study, a highly sensitive sensor based on a silicon SWG slot waveguide (SWGSW) is proposed for detecting low-concentration fluoride contaminations in water. The gap called as “slot” between the silicon slab along with cladding and the spaces between the segmented silicon rail waveguide is filled with fluoride ion-contaminated water samples as analyte for strong light–matter interaction between guiding modes of the SWG structure, resulting in greater sensitivity of the proposed sensor. The sensitivity of the proposed structure is estimated by numerical simulations as S = 615.38 nm/RIU which is comparable to the existing reported optical sensor structures based on optical waveguide and optical fibre with a smaller footprint. Additionally, the effect of variation of geometrical parameters on the transmission resonances of the proposed structure is also analyzed for the optimization of a SWG WG structure. The obtained results will be helpful to realize and design highly sensitive sensors based on the SOI platform.

Engineering of Zeno Dynamics in Integrated Photonics

Frequent observations to a quantum system modify its coherent evolution through the Zeno effect and Zeno dynamics. Generally, the measurement process destroys the evolution environment of the monitored system, making repeated observations remain a challenge. Here, using the quantum analogy experiments, we realize and engineer the Zeno effect and Zeno dynamics in optical waveguide arrays, where the optical modes correspond to distinct quantum states, and the temporal evolution is mapped into the spatial propagation. We propose a new, extensible experimental strategy for realizing an optical analog of stroboscopic measurements, which are performed by the build-in, on-demand segmented waveguide portions. The weak-to-strong stroboscopic measurements are realized, where the monitored system undergoes a transition from free evolution to optical Zeno freezing. Setting the measurements in the strong regime, the optical Zeno effect and optical Zeno dynamics are successfully generated, and their relationship is demonstrated in optics. We then propose a novel quantum Zeno slicing approach, which allows us to dynamically engineer the Hilbert space of the monitored system. This generic approach is verified by generating a series of Zeno subspaces with different measurement projectors, based on the quantum-optical analogy. The complexity of light dynamics is largely increased, providing full control of the propagation via steering Zeno dynamics. Our results pave the way for manipulation of quantum states by harnessing Zeno dynamics in integrated photonics.

Power monitoring in a feedforward photonic network using two output detectors

Abstract Programmable feedforward photonic meshes of Mach–Zehnder interferometers are computational optical circuits that have many classical and quantum computing applications including machine learning, sensing, and telecommunications. Such devices can form the basis of energy-efficient photonic neural networks, which solve complex tasks using photonics-accelerated matrix multiplication on a chip, and which may require calibration and training mechanisms. Such training can benefit from internal optical power monitoring and physical gradient measurement for optimizing controllable phase shifts to maximize some task merit function. Here, we design and experimentally verify a new architecture capable of power monitoring any waveguide segment in a feedforward photonic circuit. Our scheme is experimentally realized by modulating phase shifters in a 6 × 6 triangular mesh silicon photonic chip, which can non-invasively (i.e., without any internal “power taps”) resolve optical powers in a 3 × 3 triangular mesh based on response measurements in only two output detectors. We measure roughly 3% average error over 1000 trials in the presence of systematic manufacturing and environmental drift errors and verify scalability of our procedure to more modes via simulation.

ПОЛЯРИЗАТОР НА СЕКТОРНОМУ ХВИЛЕВОДІ, ЧАСТКОВО ЗАПОВНЕНОМУ ДІЕЛЕКТРИКОМ

In the article a polarizer based on a sector waveguide partially filled by dielectric is studied. The design of a polarizer based on a sector waveguide with smaller dimensions of the dielectric plate and a better coefficient of the standing wave rectangular waveguide - polarizer on sector waveguide - rectangular waveguide junction compared with rectangular waveguide-polarizer based on a circular waveguide -rectangular waveguide junction has been developed. The diagrams of the articulateon of the waveguide segments of the antenna-feeder path on rectangular waveguides with a polarizer on a sector waveguide and with a polarizer on a circular waveguide are shown. Formulas for the propagation constant of a sector waveguide partially filled with a dielectric and the effective permittivity of a sector waveguide are given. The dependences of the relative permittivities of a waveguide with a sector dielectric plate parallel and perpendicular to the plane of polarization of the incident wave on the average thickness of the sector dielectric plate are presented. The paper analyzes a sector waveguide partially filled with a dielectric, which has휃=휋/3 и 훷=휋/6. In this case, the scalar eigenfunction of the sector waveguide for the quasi-퐻ଷଵ wave is used. The corresponding dependences of the change in the differential phase shift in the considered wave range on the average thickness of the sector plate are presented. At small thicknesses of the phasing plates the decrease in the polarizer broadband is due to an increase in the phase shift in the long-wavelength part of the range and at large thicknesses in the short-wavelength one. By choosing the permittivity of the material, it is possible to increase the broadband of the polarizer at the expense of some increase in the length of the plate. The dependence of the standing wave coefficient of the junction rectangular waveguide - polarizer - rectangular waveguide on the value 휆/휆଴. The standing wave coefficient for the junction of rectangular waveguide - polarizer on a sector waveguide - rectangular waveguide is 3...5 % less than for a junction of rectangular waveguide - polarizer on a circular waveguide - rectangular waveguide. A polarizer based on a sector waveguide with a dielectric plate has an advantage over a polarizer based on a circular waveguide with a dielectric plate when building antenna-feeder paths on rectangular waveguides. This advantage consists in achieving a lower value of the standing wave coefficient on the waveguide section of the path with a polarizer and a shorter length of the dielectric plate – 1,25휆଴.

SWITCH-FILTER ON A RECTANGULAR WAVEGUIDE PARTIALLY FILLED BY DIELECTRIC

At article investigates a broadband switch for microwave technology, antenna-feeder paths of which are implemented on a rectangular waveguide partially filled by dielectric. Modern means of communication of the microwave range can operate for transmission through two independent antenna channels, each of which includes its own microwave transmitter. It is also provided the operation of one microwave transmitter for two antennas. The transmission of high-power signals requires the implementation devices based on rectangular waveguide partially filled by dielectric for such antenna-feeder paths. The active element is an open nonlinear structure included in a dielectric plate which located in a rectangular waveguide. The electrodynamic problem is solved by the method of eigenfunctions. In this article, the transfer coefficient T11 and plotted the graphs of the dependence of the electrical length of the waveguide segment with the open nonlinear structure on the value of the reactive conductivity of the inductive loop at fixed reactive conductivity of the open nonlinear structure is determine. The results of this article can be used in the development of broadband switches for mobile digital combined troposcatter-radio relay stations with space-diversity transmission, antenna-feeder paths of which are implemented on the rectangular waveguide partially filled by dielectric. The article developed a filter on waveguide tees partially filled by dielectric. A design based on an H-tee on a rectangular waveguide partially filled by dielectric is proposed. The equivalent circuit of the H-tee is based on the equivalent circuit in the longitudinal slot in the narrow wall of the waveguide. Such a gap interrupts the lines of the transverse surface current of the main quasi-H10 wave of a rectangular waveguide partially filled by dielectric. Numerical results are obtained for transformation ratios.

Total absorption and coherent perfect absorption in metal-dielectric-metal resonators integrated into a slab waveguide.

We propose and investigate integrated metal-dielectric-metal (MDM) resonators operating with semi-guided waves (guided modes of dielectric slab waveguides). The MDM resonators are constituted by two metal strips "buried" in the waveguide core layer and separated by a dielectric waveguide segment. We theoretically prove and numerically demonstrate that by a proper choice of the mode incidence geometry, the widths of the metal strips, and the distance between them, it is possible to achieve either total absorption of the incident wave or coherent perfect absorption (in the case of symmetric incidence of two modes on the structure). The proposed planar MDM resonators may find application as absorbers or filters in integrated optical circuits.

PRECISE Photonic Hybrid Electromagnetic Solver

PRECISE, Photonic hybRid EleCtromagnetIc SolvEr, is a Matlab-based library to model large and complex photonic integrated circuits. Each circuit is modularly described in terms of waveguide segments connected through multi-port nodes. Linear, nonlinear, and dynamical phenomena are simulated by solving the system of differential equations describing the effect to be considered. By exploiting the steady-state approximation of the electromagnetic field within each node device, the library can handle large and complex circuits even on desktop PCs. We show that the steady-state assumption is fulfilled in a broad number of applications and we compare its accuracy with an analytical model (coupled mode theory) and experimental results. PRECISE is highly modular and easily extensible to handle equations different from those already implemented and is, thus, a flexible tool to model the increasingly complex photonic circuits.

Особливості проєктування поздовжньо-співвісних хвилеводно-мікросмужкових з’єднувачів

The authors justify the use of combined longitudinal-coaxial connectors — waveguide-coaxial or waveguide-microstrip type — in new modern antenna-feeder microwave paths. Using the example of a basic coaxial waveguide-coaxial connector based on a section of a regular rectangular waveguide, the study considers the process of converting an electromagnetic wave of a regular waveguide of the main waveguide type H10 into a transverse electromagnetic wave of a coaxial line with a wave resistance (impedance) Z0 = 50 Ohm. Such a connector allows implementing good electrical parameters — matching (standing wave ratio, SWR) and linear losses — but its design is difficult to configure and cannot be reliably reproduced. However, the basic operation principles of this connector make it possible to use it as a prototype when creating modern coaxial waveguide-coaxial or waveguide-microstrip connectors. One example of such a modern connector is the sealed longitudinal-coaxial waveguide-microstrip connector based on a segment of H-shaped waveguide, shorted by an end wall on one end. Correcting the reactive component of both inductive and capacitive nature will allow achieving the required parameters of the wave impedance of the connector. With this in mind, the author has built an inductive-capacitive system consisting of a matching element in the form of a staggered fin and a corrective element in the form of a rectangular parallelepiped. To ensure the air tightness of the connector design, the segment of the coaxial line was replaced by a sealed coaxial insert, which is a serial electronic component. Particular attention was paid to the layout and design of this sealed waveguide-microstrip connector, as well as to the calculation of the overall dimensions of its elements. The article proposes an original technique for measuring the main parameters of both waveguide-coaxial and waveguide-microstrip connectors. The author forms a mathematical model of combined type connectors based on the scattering wave matrix and presents the parameters of real hermetically sealed longitudinally coaxial waveguide-microstrip connectors based on waveguide segments of various standard sizes and measured at various frequencies.

Modelling of Ring-Shaped Compound Ultrasonic Waveguides by Means of Finite Elements Method

The paper describes a technique for modelling and optimization of ring-shaped compound ultrasonic waveguides consisting of two sequentially joined segments of different materials by means of finite elements method. The possibility of using such waveguides for amplifying vibrations in amplitude has been justified in the paper. The advantage of the developed technique consists in possibility of its realization by means of standard engineering software, particularly COMSOL Multiphysics. The correctness and efficiency of the technique is proved by comparing the numerical data with the simulation results by means of transfer matrix method using equations of vibration of Euler – Bernoulli and Timoshenko type. It is shown that in compound ring-shaped waveguides two kinds of vibration modes are possible – variable-sign and constant-sign, moreover only constant-sign modes are of practical interest for amplification of vibration amplitude. Recommendations for selection of optimal geometric parameters of the waveguides are given, particularly it is shown that for ensuring maximum vibration amplification factor it is necessary to choose central angles of the waveguide segments with account for calculated dependence between amplification factor and angle, characterized by presence of several local maxima of the amplification factor. It is noted that the high accuracy of the existing semi-analytical methods for calculating and designing ring-shaped waveguides is achieved using methods based on the application of Timoshenko-type equations of vibration.

Slow Light Rainbow Trapping in a Uniformly Magnetized Gyromagnetic Photonic Crystal Waveguide

We present a hybrid gyromagnetic photonic crystal (GPC) waveguide composed of different GPC waveguide segments possessing various cylinder radii and waveguide widths but biased by a uniform external magnetic field. We demonstrate in frequency and time domains that based on the strong coupling of two counter-propagating topologically protected one-way edge states, the intriguing slow light rainbow trapping (SLRT) of electromagnetic (EM) waves can be achieved, that is, EM waves of different frequencies can be slowed down and trapped at different positions without cross talk and overlap. More importantly, due to the existence of one-way edge states, external EM waves can be non-reciprocally coupled to the SLRT waveguide channel, although the incident position of the EM wave is far away from the waveguide channel. Besides, the frequency range of the slow light states can also be easily regulated by tuning the intensity of an external magnetic field, which is very beneficial to solve the contradiction between slow light and broad bandwidth. Our results can be applied to the design of high-performance photonic devices, such as an optical buffer, optical switch, and optical filter.

Design of an Efficient Fabry-Perot Biosensor Using High-Contrast Slanted Grating Couplers on a Dual-Core Single-Mode Optical Fiber Tip

A novel and efficient Fabry-Perot biosensor on the tip of a dual-core single-mode optical fiber is proposed. The incident light emerges from one of the cores and is coupled to the second core via high-contrast silicon nitride slanted grating couplers (SGCs), separated by a silicon nitride waveguide segment disposed along the fiber tip. The challenges in designing high-contrast SGCs of very short length were overcome using an efficient analytical design approach augmented by simulations in 2D, resulting in grating designs that produce core-to-core coupling efficiencies of up to 29%. The waveguide segment separating the SGCs acts as a Fabry-Perot sensing cavity producing narrow Fabry-Perot fringes in the transmittance spectrum of the structure. Monitoring these fringes leads to bulk sensitivity and figure of merit of 50 - 100 nm/RIU and 16.67 - 33.34 (RIU $^{-1}$ ), for sensing a large range of biomaterials. The structure operates in transmission, thus eliminating the need to separate the reflected light from the incident light at the input of the fiber, which simplifies the interrogation system. Properly packaged, the fiber tip can be dipped or inserted directly into the sensing medium, which removes the need for microfluidics. The scheme enables robust, flexible, compact, and remotely-interrogated biosensors.

Structural Analysis of the US ITER ECH Transmission Line System

The electron cyclotron heating (ECH) and current drive system is one of the main plasma heating systems for ITER. It uses high-power microwave beams with the power deposition location steerable across the plasma cross section. Microwave power is conveyed via transmission lines (TLs) that run from the gyrotrons in the radio frequency building through the assembly hall and tokamak building to the ECH launchers within the tokamak vacuum vessel. The ECH system includes a vast array of interconnected TL waveguides, in-line components, and support structures. Finite element (FE) modeling provides an essential means of simulating the system, applying loads and determining deflections, rotations, forces, moments, and stresses in order to evaluate various structural and microwave transmission performance metrics. A representative FE model of the overall ECH TL system is developed in ANSYS®. This top-level model defines the centerline of the waveguide system. Waveguide segments are represented by line elements (beams and pipes) with equivalent section properties, and support structures are represented by boundary conditions. A systematic approach is used to model each ECH component with lumped masses and structurally equivalent stiffness matrices or ANSYS superelements. The top-level TL FE model is used to evaluate the various loads (thermal, vacuum, seismic, etc.) and operating scenarios. The top-level model directly calculates stresses in the straight aluminum waveguide segments. The model provides the forces and moments acting on the in-line components for detailed submodel assessments. Displacement results from the top-level analysis feed into a separate microwave performance model to help determine operational efficiency. All TL performance and thermal-structural requirements are met, as specified by the applicable codes and standards, and successfully documented in numerous technical reports and demonstrated at the final design review.