Waveguide Design Research Articles

Design, Simulation, and Characterization of MEMS-Based Slot Waveguides

This contribution presents a design approach as well as characterization results for dielectric slot waveguides fabricated in highly resistive (HR) silicon (HR-Si) designed for operation in the terahertz (THz) frequency range. The authors discuss the fundamentals of dielectric slot waveguides and the respective figures of merit. Furthermore, analytical solutions as well as numerical results from field simulations of the propagating mode are presented and discussed. Prototypes are fabricated in a process for HR-Si microelectromechanical systems (MEMSs), including a silicon-based metamaterial to mechanically support the waveguide while preserving a strong field confinement. In addition, actuator concepts to implement device functionalities, such as phase shifting capabilities, are demonstrated. The prototypes are measured and characterized using vector network analyzer (VNA)-based two-port measurements in the frequency range from 220 to 330 GHz. The devices are characterized in terms of their field confinement, loss, and effective mode index. For the first time, the authors report on the experimental validation of dielectric slot waveguides in this frequency range and provide values for the obtained losses.

Design of asymmetric waveguide for second harmonic generation based on thin film lithium niobate

Design of asymmetric waveguide for second harmonic generation based on thin film lithium niobate

Using Modeling to Select the Type of Microwave Field Emitter for Dense-Layer Grain Dryers

The microwave field is used for drying and disinfecting grains during the pre-sowing seed treatment. The use of a microwave field in these installations leads to an increase in their productivity and a decrease in the energy consumed by them. In grain dryers, where the grain moves in a dense layer without being loosened, one of the challenges in using microwave fields is ensuring sufficient uniformity of the field distribution. In this article, waveguide design options that introduce microwave radiation into the grain layer are discussed. The objective of this study was to use application software to find the optimum type of transmitter from the three options presented. A mathematical simulation of the electromagnetic field distribution was performed with the use of CST Microwave Studio software 2019 in order to evaluate and compare horn-type, rectangular, and semicircular waveguides. The data on the standing wave ratio and radiation efficiency of these types of waveguides have been reported. The specific features of the microwave electromagnetic field distribution and radiation power in the output of these waveguides have been described. The results of mathematical simulations revealed that semicircular waveguides with slot-type radiators are preferable for processing dense grain layers.

Antiresonant fiber structures based on swarm intelligence design.

In this work, we obtained a new, to the best of our knowledge, structure of anti-resonant fiber (ARF) by an adaptive particle swarm optimization (PSO) algorithm. Different from the prior method of stacking elemental parts and optimizing parameters through experience or algorithm, we decompose some classic structures into points and optimize the positions of these points through swarm intelligence. The fiber structure is reconstructed by interpolation, and some new structures with low confinement loss (CL) and high higher order mode extinction ratio (HOMER) are obtained. These novel ARFs exhibit similar structural characteristics, and are named as "the bulb-shaped ARFs". Among these structures, the minimum achieved CL is 2.21 × 10-5dB/m at 1300 nm and the maximum achieved HOMER exceeds 14,000. This work provides a method with high degree of freedom in the design of non-uniform cross-section waveguides and helps to discover new fiber structures.

Design of cycloidal rays in optical waveguides in analogy to the fastest descent problem

In this work, we present the design of cycloidal waveguides from a gradient refractive index (GRIN) medium in analogy to the fastest descent problem in classical mechanics. Light rays propagate along cycloids in this medium, of which the refractive index can be determined from relating to the descending speed under gravity force. It can be used as GRIN lenses or waveguides, and the frequency specific focusing and imaging properties have been discussed. The results suggest that the waveguide can be viewed as an optical filter. Its frequency response characteristics change with the refractive index profile and the device geometries.

Fully-Metallic Additively Manufactured Monolithic Double-Ridged Waveguide Rotman Lens in the K/Ka-Band.

This paper reports on the design and experimental validation of a fully-metallic double-ridged waveguide 10 × 10 Rotman lens additively manufactured as a single part. The wide band operation of this quasi-optical beamformer enables us to cover the uplink and downlink frequencies allocated to satellite communications in the K/Ka-band, from 17.3 GHz to 30 GHz. The feeding port design was adjusted to enable vertical printing, thus minimizing the use of supporting structures. A prototype was manufactured and tested. The reported results indicate losses in the range of 0.5 dB in the lower-frequency band and 0.8 dB in the upper-frequency band, including the waveguide transitions added for test purposes. The measured reflection and coupling coefficients remain below -11.5 dB over the operating band. The standard deviation of the residual phase error across the array ports is below 5° in simulation and below 10° in measurements. Array factors synthesized using the scattering parameters confirm the good stability of the beamforming functionality over the wide frequency band analyzed. This monolithic design is a promising step toward more integrated antenna systems, such as a compact dual-stack configuration for planar array design.

Fast design of non-uniform acoustic waveguides with prescribed eigenfrequencies

In this article we address the issue of finding acoustic and elastic resonator shapes corresponding to given eigenfrequencies. This problem has a wide range of applications spanning from ultrasonics through the music acoustics to metamaterials. We employ the previously published solution to the Webster horn equation and use it to train an artificial neural network to solve the inverse eigenvalue problem. Subsequently, it is shown how the isospectrality and scalability properties might provide a whole class of fast designed resonator shapes.

Numerical Investigation and Design of Optical On-Chip Waveguide with Engineered Dispersion for Generation of Supercontinuum-Based Frequency Combs

Numerical Investigation and Design of Optical On-Chip Waveguide with Engineered Dispersion for Generation of Supercontinuum-Based Frequency Combs

Robust Multimode Waveguide Design for Avoided Mode Crossing-Suppressed Microresonators

Microresonator-based optical frequency combs enable many potential applications, from frequency metrology to optical communication. Soliton comb generation relies on dispersion control. For bright soliton generation, it is required to have anomalous group velocity dispersion. However, the avoided mode crossing in the microresonator can disturb the local dispersion and may prevent the soliton formation. Although the avoided mode crossing may enable dark soliton generation, the unintended avoided mode crossing distorts the comb spectrum. Here, we present a robust multimode waveguide design against intermodal coupling to suppress unintended avoided mode crossing. By engineering the waveguide dimension, the phase mismatch between coupling modes can be increased, which will significantly reduce the modal coupling strength. We experimentally demonstrated the avoided mode crossing-suppressed microresonators in the AlGaAs-on-insulator platform.

Detection of Echo Signals Taking Into Account the Multipath Effect of the Waveguide and the Multispecularity of the Reflector

In the shelf zone, an experimental study was conducted on the possibility of increasing the probability of detecting echo signals against an noise background as a result of taking into account the multipath waveguide model and design features of the reflector. The possibility of increasing the tracking range and reducing the probability of false alarms is experimentally substantiated with an algorithm that uses the duration of the time interval during which a sequence of signals reflected from one reflector is observed due to the multipath propagation of signals and multispecularity of the reflected signal, if the target structure is complex and includes several offset reflectors. Recommendations are given on the choice of intervals, the sampling lengths within which summation of the energy of the reflected signals is possible. It is shown that as a result of signal power accumulation using an algorithm that partially takes into account the echo signal model, the target tracking time increases and false alarms decrease.

Design and manufacturing of waveguide of parabolic antenna using EDM process

Wireless technology was one of the main areas of research in the world of communication system today and a study of communication incomplete without an understanding of the operation and manufacturing of waveguide of parabolic antenna. Waveguide is an important electromagnetic wave transmission Component of parabolic antenna. potential benefits of parabolic antenna doesn’t required any cables to transmitte electromagnetic signal. Designing of waveguide was a most important role before its manufacturing. An attempt is made to design and manufacture the waveguide by varying cross- section using CREO software. Manufacturing of waveguide Carried out by milling, the inner pocket of waveguide was machined by Electrical discharge machining process. Which results accurate surface and suitable for travelling of electromagnetic wave without any disturbance.

Progress of Edge-Emitting Diode Lasers Based on Coupled-Waveguide Concept.

Semiconductor lasers have developed rapidly with the steady growth of the global laser market. The use of semiconductor laser diodes is currently considered to be the most advanced option for achieving the optimal combination of efficiency, energy consumption, and cost parameters of high-power solid-state and fiber lasers. In this work, an approach for optical mode engineering in planar waveguides is investigated. The approach referred to as Coupled Large Optical Cavity (CLOC) is based on the resonant optical coupling between waveguides and allows the selection of high-order modes. The state-of-art of the CLOC operation is reviewed and discussed. We apply the CLOC concept in our waveguide design strategy. The results in both numerical simulation and experiment show that the CLOC approach can be considered a simple and cost-efficient solution for improving diode laser performance.

Unidirectional beam splitting in acoustic metamaterial governed by double fractional stimulated Raman adiabatic passage

In this work, we take fractional stimulated Raman adiabatic passage (f-STIRAP) for the design of functional acoustic waveguide (WG) coupler into account. Assisted by the agreement in the form between Schrödinger equation in quantum mechanics and the coupled-mode equation of classical waves, the quantum three-level system is mapped onto the acoustic three-WG system with space-varying coupling actions between composing WGs. The output port of the coupler can be selected by adopting different superposition forms of incident waves, which is utilized to build a one-way acoustic mode converter based on double f-STIRAP. By further constructing a functional acoustic metamaterial arrayed by mode converters, a desired beam splitting behavior can be generated unidirectionally in a broadband. Our work bridges f-STIRAP and the design of acoustic metamaterial, which may have profound impacts on exploring quantum technologies for promoting advanced acoustic functional devices with simple configuration and excellent performance.

Single-frequency violet and blue laser emission from AlGaInN photonic integrated circuit chips.

Chip-based, single-frequency and low phase-noise integrated photonic laser diodes emitting in the violet (412 nm) and blue (461 nm) regime are demonstrated. The GaN-based edge-emitting laser diodes were coupled to high-quality on-chip micro-resonators for optical feedback and mode selection resulting in laser self-injection locking with narrow emission linewidth. Multiple group III-nitride (III-N) based photonic integrated circuit chips with different waveguide designs including single-crystalline AlN, AlGaN, and GaN were developed and characterized. Single-frequency laser operation was demonstrated for all studied waveguide core materials. The best side-mode suppression ratio was determined to be ∼36 dB at 412 nm with a single-frequency laser emission linewidth of only 3.8 MHz at 461 nm. The performance metrics of this novel, to the best of our knowledge, type of laser suggest potential implementation in next-generation, portable quantum systems.

SiN waveguides for ultra-broadband visible-telecom photon pairs

We propose simple rectangular cross-section, few-cm long SiN waveguide designs capable of generating ultra-broadband frequency-correlated photon pairs via SFWM, exceeding an octave in bandwidth spanning the visible-to-telecom wavelengths ( $$\sim$$ 700–1700 nm for $$\sim$$ 1- $$\upmu$$ m pump) with a spectral brightness of $$>2.5\times 10^4$$ photon pairs/s/nm/mW $$^2$$ . Such compact sources, spanning the entire telecom spectrum (across O, E, S, C, L, and U bands) on one side and covering most of the major atomic transitions used in ultracold gases and solid-state based quantum memories on the other side, could potentially be employed in large-scale multi-channel hybrid (free space + fiber) quantum networking schemes in addition to the heralding of telecom single photons by utilizing high efficiency visible detectors.

Simplified design of a hybrid plasmonic waveguide to maximize propagation length

We design a waveguide for maximizing propagation length using the COMSOL environment based on the finite element method. The proposed design aims to achieve a high propagation distance and a constrained normalized TM mode. The range of propagation length (5−12)mm and the normalized TM mode area range can be achieved in the range of gap thickness (2−17)nm, silver thickness (1−6)nm, and arc radius 50nm. A trade-off will be between having a small mode area and a long propagation length in a successful hybrid plasmonic waveguide (HPW) design. The findings show that, with such a small mode area and long propagation length of SPPs at the wavelength 1.55μm, the suggested waveguide may avoid the unavoidable loss-confinement trade-off, which is desirable for integrated circuits. Balancing the arc radius and gap thickness at the widely used wavelength of 1.55 µm typically yields the required results. A substantial confinement coefficient has been achieved, essential in the HPW field.

1.8-µm laser operation based on femtosecond-laser direct written Tm:YVO4 cladding waveguides.

In this work, we have demonstrated tunable 1.8-µm laser operation based on a Tm:YVO4 cladding waveguide fabricated by means of femtosecond laser direct writing. Benefiting from the good optical confinement of the fabricated waveguide, efficient thulium laser operation, with a maximum slope efficiency of 36%, a minimum lasing threshold of 176.8 mW, and a tunable output wavelength from 1804 to 1830nm, has been achieved in a compact package via adjusting and optimizing the pump and resonant conditions of the waveguide laser design. The lasing performance using output couplers with different reflectivity has been well studied in detail. In particular, due to the good optical confinement and relatively high optical gain of the waveguide design, efficient lasing can be obtained even without using any cavity mirrors, thereby opening up new possibilities for compact and integrated mid-infrared laser sources.

Design of new wideband waveguide Magic‐T for X‐band applications

AbstractThe design and fabrication of low loss and wideband Magic‐T with 10 dB return loss (RL) bandwidth over 40% is proposed for X‐band application, which can be used in monopulse comparator network. The proposed Magic‐T is composed of WR90 waveguides include an exponentially conducting cone, metallic multistep l‐shaped septum, and some other conducting posts. By implementation of these optimized conducting cone, septum, and posts, the 20 dB RL bandwidth over 36% is achieved with very low insertion loss (IL) (<0.15 dB) at each port. Moreover, high isolation (>40 dB) across all port over X‐band is another feature of the proposed Magic‐T. The equal power division (in amplitude and phase) at H‐arm and phase cancellation of input power at E‐arm introduce the proposed Magic‐T as a good candidate for sum/difference comparator network for monopulse application. Validation of the simulation results by experimental ones proves the wideband RL, low IL, and high isolation coefficient of the proposed high‐power Magic‐T as well.

Efficient multimodal-based shape optimization of acoustic horns with application to subwavelength perfect transmission

This paper presents an efficient multimodal-based shape optimization method for maximizing sound radiation from open-ended acoustic horns. The proposed method tightly integrates the improved multimodal admittance method with interpolation-based geometry parameterization to allow flexible design degrees of freedom, with computational cost for gradient evaluation nearly independent of the number of design variables. We demonstrate that our method outperforms an existing discrete-model-based approach in solving typical narrowband and wideband horn design problems, offering increased efficiency and flexibility. For the first time, we achieve novel resonator-like waveguide designs with subwavelength perfect transmission well below the cut-off frequency of classical horns by performing shape optimization. The optimal waveguides exhibit single to multiple transmission peaks or bandpass characteristics. We validate the designs numerically and experimentally and demonstrate that the perfect transmission is related to the excitation of the acoustic resonant mode. Our method has potential applications in the design of compact high-output subwoofers, anechoic duct terminations, and acoustic filters.

Crosstalk prohibition at the deep-subwavelength scale by epsilon-near-zero claddings

Abstract To prevent the crosstalk between adjacent waveguides in photonic integrated circuits, the minimum thickness of the cladding layers is around half a wavelength, which imposes a fundamental limitation to further integration and miniaturization of photonic circuits. Here, we reveal that epsilon-near-zero claddings, either isotropic or anisotropic, can break the above bottleneck by prohibiting the crosstalk for the modes with magnetic field polarized in the z direction at a deep-subwavelength thickness (e.g., λ 0/30, λ 0 is the free-space wavelength), therefore bestowing ultra-compact waveguide systems. The physical origin of this remarkable effect attributes to the divergent impedance of epsilon-near-zero materials far beyond those of dielectric or epsilon-negative claddings. Through full-wave simulations and microwave experiments, we have verified the effectiveness of the ultrathin epsilon-near-zero cladding in crosstalk prohibition. Our finding reveals the significant impact of impedance difference in waveguide designs and opens a promising route toward ultra-compact photonic chips.