Waveguide Ports Research Articles

A compact plasmonic MOS-based 2×2 electro-optic switch

Abstract We report on a three-waveguide electro-optic switch for compact photonic integrated circuits and data routing applications. The device features a plasmonic metal-oxide-semiconductor (MOS) mode for enhanced light-matter-interactions. The switching mechanism originates from a capacitor-like design where the refractive index of the active medium, indium-tin-oxide, is altered via shifting the plasma frequency due to carrier accumulation inside the waveguide-based MOS structure. This light manipulation mechanism controls the transmission direction of transverse magnetic polarized light into either a CROSS or BAR waveguide port. The extinction ratio of 18 (7) dB for the CROSS (BAR) state, respectively, is achieved via a gating voltage bias. The ultrafast broadband fJ/bit device allows for seamless integration with silicon-on-insulator platforms for low-cost manufacturing.

Acoustic Vector-Corrected Impedance Meter

We describe the development of a novel instrument intended for the measurement of the acoustical reflection coefficient of materials. The instrument effectively implements a one-port vector-corrected network analyzer in the acoustic, rather than the electromagnetic, domain. Employing the well-documented methods of error correction familiar to microwave engineers, this instrument permits automated measurement of an acoustic impedance presented to a waveguide port. A dual-directional coupler allows a working frequency range of well over an octave. In principle, a set of six couplers would allow measurement from 100 to 50000 Hz.

Novel all-optical logic gates based photonic crystal waveguide using self imaging phenomena

All-optical logic gate with multifunctional performance have been designed theoretically in a two-dimensional photonic crystal waveguide (PCW) structure using multimode interference principle. A two dimensional finite-difference time domain (2D-FDTD) was employed in our numerical simulations. It is shown that by switching the optical signal to different input waveguide ports, the proposed device can function as XOR, OR, NOR and NOT gates simultaneously or individually. It is also shown that by a combination of photonic band gap and total internal reflection effects in PCWs, the device can operate for both, transverse electric (TE) and transverse magnetic (TM) polarizations. Our simulation results show that the optimized devices have very good transmission efficiencies, a broad frequency range and the contrast ratio are extending to high than 21 dB for TE and 17 dB for TM polarization. The total width and length of the devise are 2.16 and 8.20 \(\upmu \hbox {m}\) respectively achieving miniaturization. It is a kind of promising device for next generation logic optical circuits, ultrahigh speed signal processing, and future photonic crystal based all-optical integrated circuits.

Ring-Shaped Substrate Integrated Waveguide Wilkinson Power Dividers/Combiners

This paper proposes and presents a class of substrate integrated waveguide (SIW) power dividers/combiners based on a modified Wilkinson architecture. The proposed design consists of a ring-type circuit of 1.5 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> length with three waveguide ports. Impedance variation without affecting cutoff frequency and integration of isolation resistance are the two major limitations in connection with the design of SIW Wilkinson structures. Central ring part with different thickness ensures different impedance in the first proposed scheme while the half-mode SIW in the second option. As for the second limitation, the optimal configuration of integrating the isolation resistance is studied. A version without resistance is also examined using a broad-wall series slot. To validate the proposed concept, a bilayered circuit with standard Printed circuit board prototype was fabricated and measured. A table summarizing performances of all the proposed circuits shows a bandwidth of around 25% at the 10 dB reference. A negligible additional insertion loss is observed. The proposed design techniques are found useful at millimeter-wave frequencies where reduced physical dimensions make a circuit configuration suitable for low-cost implementation. This concept is also valid for rectangular waveguide counterparts.

On-chip near-infrared optical spectrometer based on single-mode Epo waveguide and gold nanoantennas

We report about optical spectrometry using gold nanostructures printed on top of an integrated optical waveguide. The optical waveguide is a single-mode buried waveguide made from a combination of photo-polymerizable materials and is fabricated by photolithography on a glass substrate. To detect the electric field inside the waveguide, a gold nanocoupler array of thin lines (50 nm thick and 8 μm in length) is embedded on top of the aforementioned waveguide. They are produced by e-beam lithography. Both waveguide ports are polished, and the output port, in particular, is coated with a thin gold layer to assimilate a mirror and hence, it enables the creation of stationary waves inside the structure. Stationary waves generated inside the guide constitute a spatial interferogram. Locally, light is out-coupled using the nanocouplers and allows measuring the interferogram structure. The resulting pattern is imaged by a vision system involving an optical microscope with the objective lenses of different magnifications and a digital camera mounted on top of the microscope. The 5× objective lens demonstrates a superior performance in retrieving the investigated spectrum compared to 20× and 100× objectives. Fast Fourier transform is performed on the captured signal to extract the spectral content of the measured signal.

A Non-Contact Submillimeter-Wave $S$-Parameters Measurement Technique for Multiport Micromachined Devices

This paper presents a novel non-contact broadband on-wafer S-parameter measurement technique for submillimeter-wave and terahertz applications. The proposed method enables S-parameters measurement of multi-port micromachined devices using a two-port measurement setup. In this method, a small fraction of the signal at each waveguide port is weakly coupled to free space using a small array of reflection-canceling slots which are then measured by an open-ended waveguide probe. The S-parameters of the device-under-test are calculated from the measured signals obtained from each port and from that of a reference match waveguide. A broadband waveguide slot array antenna with high return loss is designed as a matched load to terminate all ports of the device except the input port. To assess the reliability and accuracy of the proposed measurement method, three different micromachined waveguide directional couplers are designed, fabricated, and tested. Multiple apertures on the common wall between the adjacent waveguides are designed and optimized to achieve high directivity couplers over a broad frequency range. The measured S-parameters of the couplers are shown to be in good agreement with the simulations, which indicates the accuracy of the proposed measurement method.

Time-Domain Absorbing Boundary Terminations for Waveguide Ports Based on State-Space Models

Absorbing boundary conditions for waveguide ports in time domain are important elements of transient approaches to treat RF structures. A successful way to implement these termination conditions is the decomposition of the transient fields in the absorbing plane in terms of modal field patterns. The absorbing condition is then accomplished by transferring the wave impedances (or admittances) of the modes to time domain, which leads to convolution operations involving Bessel functions and integrals of Bessel functions. This paper presents a new alternative approach: the convolution operations are approximated by appropriate state-space models whose system responses can be conveniently computed by standard integration schemes. These schemes are indispensable for transient simulations anyhow. Sufficiently far away from the cutoff frequency, a wideband match is achieved.

A Novel Local Waveguide Port (LWP) Excitation Based on FDTD Algorithm

A Novel Local Waveguide Port (LWP) Excitation Based on FDTD Algorithm

Numerical simulation of multipactor phenomenon on the surface of cylinder window disk

A particle model that is based on Monte Carlo particle simulation arithmetic is built up to investigate the multipactor behavior on the surface of cylinder window disk in pill-box window. The regime of multipactor in the inhomogeneous electric field is obtained. The simulation results prove that the interaction between secondary electrons and window disk is sustained by magnetic field force on the upstream side. The multipactor phenomenon acts intensively in the area with a great electric field. The ponderomotive force does not devote any effort to multipactor on the upstream side. On the downstream side, the multipactor cannot be excited without strong enough surface electrostatic field because of the positive magnetic field force. With the increase of transmitting power, secondary electrons can obtain more energies. Due to the effect of ponderomotive force, the multipactor region transfers from the area with powerful electric field to the weak one on the downstream side. Besides, the resistance effect of electrostatic isolation on multipactor is also confirmed in the input port of cylinder waveguide.

Broadband coplanar‐waveguide and microstrip low‐noise amplifier hybrid integrations for K‐band substrate integrated waveguide applications on low‐permittivity substrate

K-band low-noise amplifier (LNA) chips are integrated in low-permittivity coplanar waveguide (CPW) and microstrip (MS) structures and are interconnected with substrate integrated waveguide (SIW) ports for direct applications in hybrid SIW technology. A commercial Hittite LNA chip is employed, and special transitions provide the interface between CPW or MS and SIW. The LNA with SIW-to-CPW transitions achieves more than 20 dB gain between 18 and 26.5 GHz, and input/output return losses remain below 10 dB between 21.5 and 26.5 GHz. Related design values for the LNA integration within SIW-to-MS transitions are: the gain is greater than 21 dB; the input/output return loss is better than 12 dB over the entire frequency range. Measurements of a back-to-back SIW-to-CPW transition are provided to put these values in perspective. The maximum noise figures are measured to be better than 4.6 and 4.2 dB, respectively, between 18 and 26.5 GHz. A comparison with measurements performed with an evaluation board supplied by the LNA manufacturer demonstrates successful K-band LNA chip integrations within CPW/MS and SIW.

A New Method to Analyze Broadband Antenna-Radome Interactions in Time-Domain

Based on the new time-domain finite integration theorem (TDFIT), a fast and accurate method is proposed to analyze broadband antenna-radome interactions in time domain. Due to the time-domain feature, broadband characteristic is obtained in a single simulation. In numerical simulations, the antenna array is placed inside an enclosed or semi-closed radome by using a presented local waveguide port. The staircase error in traditional finite-difference time-domain method is reduced by a novel conformal technique. An illustrating broadband antenna array with radome, operating at millimeter wave frequency is analyzed and optimized to show the high performance of our method. A new broadband transmittance of the antenna-radome system is proposed to incorporate the side lobe effect, and it is treated as the objective function to optimize the parameters of the antenna-radome system. Furthermore, the full wave simulation, combined with an artificial neural network (ANN) algorithm, is utilized to accelerate the antenna-radome optimization. About half of the time for computation has been reduced.

Temperature-compensated fiber-optic 3D shape sensor based on femtosecond laser direct-written Bragg grating waveguides

Temperature-compensated 3D fiber shape sensing is demonstrated with femtosecond laser direct-written optical and Bragg grating waveguides that were distributed axially and radially inside a single coreless optical fiber. Efficient light coupling between the laser-written optical circuit elements and a standard single-mode fiber (SMF) was obtained for the first time by 3D laser writing of a 1 × 3 directional coupler to meet with the core waveguide in the fusion-spliced SMF. Simultaneous interrogation of nine Bragg gratings, distributed along three laterally offset waveguides, is presented through a single waveguide port at 1 kHz sampling rate to follow the Bragg wavelength shifts in real-time and thereby infer shape and temperature profile unambiguously along the fiber length. This distributed 3D strain and thermal sensor is freestanding, flexible, compact, lightweight and opens new directions for creating fiber cladding photonic devices for a wide range of applications from shape and thermal sensing to guidance of biomedical catheters and tools in minimally invasive surgery.

High isolation dual‐port MIMO antenna

A compact dual-port multiple-input multiple-output (MIMO) antenna is proposed for 2.4 GHz wireless local area network systems. The radiation element consists of a monopole and a patch ring with two cuts, through which a coplanar waveguide port and a slotline port are constructed. The current distributions of the proposed antenna for both ports excited are simulated and analysed, respectively. According to the measurement results of the manufactured antenna prototype, the isolation between these two ports over the operating frequencies is better than –35 dB and the cross-polarisation radiation levels are less than –45 dB at the main direction. Finally, the proposed antenna has excellent isolation not only at the feed ports, but also in the radiation patterns.

Adjustment of H -plane waveguide tee-junction circulator using a circular post gyromagnetic resonator

The reflection parameters of the right-angled waveguide tee-junction containing a dielectric post resonator are, in general, except for one position of the resonator, different at the main and the side waveguide ports. Its description therefore requires two different definitions of its port variables. One purpose of this article is to locate the position which displays electrical symmetry at the three ports. This is done at a frequency of 13.25 GHz in WR75 waveguide. Another is to replace the dielectric resonator by a magnetized gyromagnetic one in order to produce a degree-1 H-plane tee-junction circulator. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:55–58, 2014.

A compact frequency selective stop-band splitter by using Fabry—Perot nanocavity in a T-shaped waveguide

By utilizing a Fabry—Perot (FP) nanocavity adjacent to T-shaped gap waveguide ports, spectrally selective filtering is realized. When the wavelength of incident light corresponds to the resonance wavelength of the FP nanocavity, the surface plasmons are captured inside the nanocavity, and light is highly reflected from this port. The resonance wavelength is determined by using Fabry—Perot resonance condition for the nanocavity. For any desired filtering frequency the dimension of the nanocavity can be tailored. The numerical results are based on the two-dimensional finite difference time domain simulation under a perfectly matched layer absorbing boundary condition. The analytical and simulation results indicate that the proposed structure can be utilized for filtering and splitting applications.

Higher Order Time-Domain Finite-Element Method for Microwave Device Modeling With Generalized Hexahedral Elements

A novel higher order and large-domain Galerkin-type finite-element method (FEM) is proposed for direct 3-D electromagnetic modeling in the time domain. The method is implemented in the time-domain finite-element method (TDFEM) analysis of multiport microwave waveguide devices with arbitrary metallic and dielectric discontinuities. It is based on the geometrical modeling using Lagrange-type interpolation generalized hexahedra of arbitrary geometrical-mapping orders, field expansion in terms of hierarchical curl-conforming 3-D polynomial vector basis functions of arbitrarily high field-approximation orders, time stepping with an implicit unconditionally stable finite-difference scheme invoking the Newmark-beta method, and mesh truncation introducing the waveguide port boundary condition. Numerical examples demonstrate excellent accuracy, efficiency, stability, convergence, and versatility of the presented method, and very effective large-domain TDFEM models of 3-D waveguide discontinuities using minimal numbers of large conformal finite elements and minimal numbers of unknowns. The results obtained by the higher order TDFEM are in an excellent agreement with indirect solutions obtained from the FEM analysis in the frequency domain (FD) in conjunction with the discrete Fourier transform and its inverse, as well as with measurements and with alternative full-wave numerical solutions in both time and FDs.

Digital-beam-forming extension for a two-channel E-band FMCW-sensor

A general purpose two-channel Frequency modulated continuous wave (FMCW)-sensor in E-band is extended to a digital-beam-forming (DBF) system. The hardware extension contains a transmit multiplexer, which allows switching of the (DBF) transmit signal of the sensor to any of 32 linearly arranged waveguide antennae. To maintain the spatial sampling condition by λ/2 element distance, the antenna ports are arranged in the E-plane. The ports can directly radiate or serve as primary radiators of a cylindrical dielectric lens focusing in the H-plane. By realizing the hardware extension based on a metal-backed substrate, some novel radio frequency (RF) structures became necessary. One of these structures is a special twisting microstrip-to-waveguide-transition to connect the switching matrix to waveguide ports arranged in the E-plane. Key elements of the multiplexer are commercially available pin-diode-based MMIC-switches in microstrip technology. To lower the inductance of the interconnects, they are embedded in cavities in the metal-backed RF-substrate. RF interconnects between the sensor and the extension are all done with waveguide ports. Further interconnects between the module and the extension are low-frequency or digital and are led via cables and removable plugs. Both module and extension can be powered separately. This gives an easily mountable extension for making a two-dimensional (2D) DBF sensor out of a 1D FMCW-sensor.

45$^{\circ}$-Mirror Terminated Polymer Waveguides on Silicon Substrates

The 45°-mirror terminated polymer waveguides fabricated on a silicon substrate are demonstrated for on-chip out-of-plane optical interconnects. The silicon 45° microreflectors are fabricated on an orientation-defined (100) silicon substrate by using anisotropic chemical wet etching. On using a photolithography process, we observe two vertically bending paths at the input and output ports of polymer waveguide on a silicon substrate with 45° microreflectors. The transmission efficiency of -3.77 dB is measured for a 0.5-cm polymer waveguide combined with the 45° microreflectors. The optical loss occurring at the 45°-mirror is -0.27 dB. The channel-to-channel crosstalk for the 250-μm pitch is less than -40 dB. The wider alignment tolerance up to ±15 μm would facilitate the active-device assembly on a silicon substrate.

Manipulation of micro-particles through optical interference patterns generated by integrated photonic devices

Micro-particle transport and switch governed by guided-wave optical interference are presented. The optical interference, occurring in a directional coupler and a multi-mode interferometer made by inverted rib waveguides, results in a specific evanescent field dependent on wavelength. Through a detailed theoretical analysis, the field of induced optical force shows a correlative pattern associated with the evanescent field. Experimental results demonstrate that 10 μm polystyrene beads are propelled with a trajectory subject to the interference pattern accordingly. By launching different wavelengths, the polystyrene beads can be delivered to different output waveguide ports. Massive micro-particle manipulation is applicable.

A dispersion compensation procedure to extend pulse-echo defects location to irregular waveguides

Abstract A time–frequency signal processing procedure aimed at extending pulse-echo defect detection methods based on guided waves to irregular waveguides is proposed. In particular, the procedure returns the distance traveled by a guided wave that has propagated along a waveguide composed by segments with different dispersive properties by processing the detected echo signal. To such aim, the acquired signal is processed by means of a two-step procedure. First, a warped frequency transform (WFT) is used to compensate the dispersion of the guided wave due to the traveled distance in a portion of the waveguide that is assumed as reference. Next, a further compensation is applied to remove from the warped signal the group delay introduced by the remaining irregular portion of the waveguide. Thanks to this processing strategy, the actual distance traveled by the wave in the regular portion of the irregular waveguide is revealed. Thus, the proposed procedure is suitable for automatically locate defect-induced reflections in irregular waveguides and can be easily implemented in real applications for structural health monitoring purposes. The potential of the procedure is demonstrated and validated numerically by simulating and processing Lamb waves propagating in waveguides made up of different uniform, tapered and curved segments.