Reconfigurable Waveguide Research Articles

Transformable origami-inspired acoustic waveguides

Using foldable origami-like structures, we design reconfigurable and switchable acoustic waveguides composed of interconnected periodic arrays of hollow tubes to manipulate and guide sound. We demonstrate both numerically and experimentally that upon application of external deformation, the structure is folded and transformed to one-, two-, and three-dimensional waveguide in which sound waves travel through the tubes. The proposed design expands the ability of existing acoustic waveguides by enabling tunability induced by reversible deformation and folding shape transformation over a wide range of frequencies, opening avenues for the design of novel tunable waveguides and adaptive sound filters.

Active demultiplexing of single photons from a solid‐state source

AbstractA scheme for active temporal‐to‐spatial demultiplexing of single photons generated by a solid‐state source is introduced. The scheme scales quasi‐polynomially with photon number, providing a viable technological path for routing n photons in the one temporal stream from a single emitter to n different spatial modes. Active demultiplexing is demonstrated using a state‐of‐the‐art photon source—a quantum‐dot deterministically coupled to a micropillar cavity—and a custom‐built demultiplexer—a network of electro‐optically reconfigurable waveguides monolithically integrated in a lithium niobate chip. The measured demultiplexer performance can enable a six‐photon rate three orders of magnitude higher than the equivalent heralded SPDC source, providing a platform for intermediate quantum computation protocols. image

Beam Switching Dual Polarized Antenna Array With Reconfigurable Radial Waveguide Power Dividers

In this paper, we propose a new method for designing dual polarized beam switching antennas by using reconfigurable radial waveguides excited by central probes and feeding multiple radiating elements. The power distribution of the radiating elements is controlled by cylindrical electromagnetic bandgap structures made of metallic wires loaded with PIN diodes. The proposed technique allows azimuth beam switching and multiple beams, with arbitrary and well controlled polarizations, using low dc voltage. First, a new rectangular periodic structure is used as a model for analyzing the transmission and reflection coefficients for different diode states. Then, numerical and experimental results are presented for a reconfigurable radial waveguide power divider and for the radiating elements. Finally, numerical and experimental results are presented and discussed for a complete dual polarized antenna operating at wireless local area network (WLAN) 5 GHz band (5.18–5.825 GHz).

Modeling and design of two-dimensional membrane-type active acoustic metamaterials with tunable anisotropic density.

A two-dimensional active acoustic metamaterial with controllable anisotropic density is introduced. The material consists of composite lead-lead zirconate titanate plates clamped to an aluminum structure with air as the background fluid. The effective anisotropic density of the material is controlled, independently for two orthogonal directions, by means of an external static electric voltage signal. The material is used in the construction of a reconfigurable waveguide capable of controlling the direction of the acoustic waves propagating through it. An analytic model based on the acoustic two-port theory, the theory of piezoelectricity, the laminated pre-stressed plate theory, and the S-parameters retrieval method is developed to predict the behavior of the material. The results are verified using the finite element method. Excellent agreement is found between both models for the studied frequency and voltage ranges. The results show that, below 1600 Hz, the density is controllable within orders of magnitude relative to the uncontrolled case. The results also suggest that simple controllers could be used to program the material density toward full control of the directivity and dispersion characteristics of acoustic waves.

Fusion of Renewable Ring Resonator Lasers and Ultrafast Laser Inscribed Photonic Waveguides.

We demonstrated the monolithic integration of reusable and wavelength reconfigurable ring resonator lasers and waveguides of arbitrary shapes to out-couple and guide laser emission on the same fused-silica chip. The ring resonator hosts were patterned by a single-mask standard lithography, whereas the waveguides were inscribed in the proximity of the ring resonator by using 3-dimensional femtosecond laser inscription technology. Reusability of the integrated ring resonator – waveguide system was examined by depositing, removing, and re-depositing dye-doped SU-8 solid polymer, SU-8 liquid polymer, and liquid solvent (toluene). The wavelength reconfigurability was validated by employing Rhodamine 6G (R6G) and 3,3′-Diethyloxacarbocyanine iodide (CY3) as exemplary gain media. In all above cases, the waveguide was able to couple out and guide the laser emission. This work opens a door to reconfigurable active and passive photonic devices for on-chip coherent light sources, optical signal processing, and the investigation of new optical phenomena.

Ultralow loss visible surface plasmon based waveguides formed in indium-tin-oxide coated Fe-doped LiNbO3 slabs.

Visible reconfigurable waveguides were evidenced in a composite system formed with indium-tin-oxide (ITO) films coated on iron-doped lithium noibate (LN) slabs. Surface plasmon polaritions (SPPs) excited at the ITO/LN interface were believed to be behind the observed light guiding, which is inherent with superlow loss for its sub-nanometer modified layer. The forward near-surface-normal scattering and accompanying reduction of the specular reflectivity in the front ITO/LN interface are consistent with SPP excitation.

A Generalized Lossy Transmission-Line Model for Tunable Graphene-Based Transmission Lines with Attenuation Phenomenon.

To investigate the frequency shift phenomenon by inserting graphene, a generalized lossy transmission-line model and the related electrical parameter-extraction theory are proposed in this paper. Three kinds of graphene-based transmission lines with attenuation phenomenon including microstrip line, double-side parallel strip line, and uniplanar coplanar waveguide are analyzed under the common conditions where different chemical potentials are loaded on graphene. The values of attenuation constant and phase constant, and the real and imaginary parts of the characteristic impedance of transmission lines are extracted to analyze in details. When the attenuation constant and the reactance part of the characteristic impedance are approximately equal to zero, this kind of transmission line has low or zero insertion loss. On the contrary, the transmission line is under the radiation mode with obvious insertion loss. The phase constant changes linearly under the transmission mode and can be varied with changing of chemical potentials which attributes to the property of frequency tunability. Furthermore, a bandwidth reconfigurable uniplanar coplanar waveguide power divider is simulated to demonstrate that this theory can be applied to the design of three-port devices. In summary, this work provides a strong potential approach and design theory to help design other kinds of terahertz and mid-infrared reconfigurable devices.

Reconfigurable hybrid metamaterial waveguide system at terahertz regime.

We propose an optically controlled reconfigurable hybrid metamaterial waveguide system at terahertz frequencies, which consists of a two dimensional gold cut wire array deposited on top of a dielectric slab waveguide. Numerical findings reveal that this device is able to realize dynamic transformation from double electromagnetically induced transparency like material to ultra-narrow band guided mode resonance (GMR) filter by controlling the optically excited free carriers in gallium arsenide pads inserted between the gold cut wires. During this reconfiguration process of resonance modes, high quality factors up to ~104 and ~118 for the two EIT-like peaks and up to ~578 for the GMR filter are obtained.

Re-configurable multi-level temperature sensing by ultrasonic “spring-like” helical waveguide

This paper introduces a novel technique for multi-level temperature measurement using a single reconfigurable ultrasonic wire waveguide that is configured in the form of a helical spring. In this embodiment, the multiple sensing levels located along the length of the helical waveguide wire can be repositioned by stretching or collapsing the spring to provide measurements at different desired spacing in a given area/volume. This method can measure over a wide range of temperatures. The transduction is performed using Piezo-electric crystals that are attached to one end of the waveguide which act as transmitter as well as receiver. The wire will have multiple reflector embodiments (notches was used here) that allow reflections of input L(0,1) mode guided ultrasonic wave, in pulse echo mode, back to the crystal. Using the time of fight measurement at multiple predefined reflector locations, the local average temperatures are measured and compared with co-located thermocouples. The finite element modeling simulation was used to study the effect of excitation frequency and the mean coil diameter of the “spring-like” waveguide. This technique improves on the limitations of a straight waveguide technique earlier reported.

A reconfigurable waveguide for energy-efficient transmission and local manipulation of information in a nanomagnetic device.

Spin-wave-based devices promise to usher in an era of low-power computing where information is carried by the precession of the electrons' spin instead of dissipative translation of their charge. This potential is, however, undermined by the need for a bias magnetic field, which must remain powered on to maintain an anisotropic device characteristic. Here, we propose a reconfigurable waveguide design that can transmit and locally manipulate spin waves without the need for any external bias field once initialized. We experimentally demonstrate the transmission of spin waves in straight as well as curved waveguides without a bias field, which has been elusive so far. Furthermore, we experimentally show a binary gating of the spin-wave signal by controlled switching of the magnetization, locally, in the waveguide. The results have potential implications in high-density integration and energy-efficient operation of nanomagnetic devices at room temperature.

K-Band Fully Reconfigurable Pseudo-Elliptic Waveguide Resonator Filter with Tunable Positive and Negative Couplings

K-Band Fully Reconfigurable Pseudo-Elliptic Waveguide Resonator Filter with Tunable Positive and Negative Couplings

Optical waveguides in lithium niobate: Recent developments and applications

The state of the art of optical waveguide fabrication in lithium niobate is reviewed, with particular emphasis on new technologies and recent applications. The attention is mainly devoted to recently developed fabrication methods, such as femtosecond laser writing, ion implantation, and smart cut waveguides as well as to the realization of waveguides with tailored functionalities, such as photorefractive or domain engineered structures. More exotic systems, such as reconfigurable and photorefractive soliton waveguides, are also considered. Classical techniques, such as Ti in-diffusion and proton exchange, are cited and briefly reviewed as a reference standpoint to highlight the recent developments. In all cases, the application-oriented point of view is preferred, in order to provide the reader with an up-to date panorama of the vast possibilities offered by lithium niobate to integrated photonics.

A Miniaturized Microfluidically Reconfigurable Coplanar Waveguide Bandpass Filter With Maximum Power Handling of 10 Watts

In this paper, a microfluidically reconfigurable coplanar waveguide (CPW) filter is presented with a tuning range of $\sim$ 1.6:1 and four different states. The passband frequency of the filter is changed based on employing the capacitive loading effect of a liquid metal placed on top of each CPW resonator using three parallel micro-channels. In addition, because of the loading effect of the metal bridges, miniaturization by a factor of 40% is achieved. The filter is digitally tuned from 3.4 to 5.5 GHz with an insertion loss of less than 5.0 dB and a relative bandwidth of 5 $\pm$ 0.35%. The RF power-handling capability of the filter is characterized using a customized measurement setup. It is observed that the filter can be used for input RF powers of up to $\sim$ 20 W for short-duration excitation conditions and 10 W for high-average-power excitation conditions. The filter is realized using common printed circuit board technology and a polydimethylsiloxane structure. Design methodology, simulation, and measurement results of the filter prototype are presented.

Magnetically Reconfigurable SIW Antenna with Tunable Frequencies and Polarizations

We propose a novel reconfigurable substrate-integrated waveguide (SIW) slot antenna with frequency and polarization tunability. Based on the multimode characteristic of SIW resonant cavity, the antenna works in two bands and radiates in linear or circular polarizations by tuning a crossed radiation slot. With the loading of ferrite slabs, the polarizations and operation frequencies of the antenna can be tuned by varying the bias magnetic field (BMF). The proposed design is verified by both simulations and experiments. The measurement results show that the tunable frequency range is more than 8.1% in the lower frequency band (from 8.98 to 9.74 GHz) and 5.5% in the higher frequency band (from 9.98 to 10.54 GHz). The antenna gain is more than 5.1 dBi within the frequency tuning range. The radiation pattern of the antenna is almost not affected by the changes in the BMF.

Design of Dual-band Reconfigurable Substrate Integrated Waveguide Cavity-backed Slot Antenna Array

ABSTRACTIn this paper, a dual-band reconfigurable substrate-integrated waveguide (SIW) cavity-backed slot antenna 1 × 8 linear array is presented with dual states. The proposed SIW antenna array combines the features of the conventional metalized cavity-backed patch arrays such as surface wave suppression, high efficiency with low-manufacturing cost. The basic element has been designed, fabricated and the performance has been verified in the outdoor antenna test range. Here, PIN diodes have been used as a switching device to achieve the reconfigurability with dual-band operation. A corporate feed network has been designed and integrated with the antenna to make it as a linear array.

Reconfigurable and tunable flat graphene photonic crystal circuits.

Photonic crystal waveguides and circuits are one of the basic modules for integrated photonic devices. They mainly rely on photonic bandgaps to achieve light confinement and manipulation. Herein, we propose a novel general principle or method to achieve reconfigurable and tunable flat graphene photonic crystals (FG-PCs) by selectively electrostatic gating a layer of graphene with periodic gold electrodes. The tunable flat photonic bandgap structure of the FG-PCs as a function of the Fermi level is investigated. Reconfigurable FG-PC defect waveguides and cavities created by external patterned-gate-voltage control are also proposed and discussed. The features of reconfigurable/tunable FG-PCs will add more flexibility and capabilities for the single chip integration of graphene-based integrated photonic devices.

On-chip generation and manipulation of entangled photons based on reconfigurable lithium-niobate waveguide circuits.

A consequent tendency toward high-performance quantum information processing is to develop the fully integrated photonic chip. Here, we report the on-chip generation and manipulation of entangled photons based on reconfigurable lithium-niobate waveguide circuits. By introducing a periodically poled structure into the waveguide circuits, two individual photon-pair sources with a controllable electro-optic phase shift are produced within a Hong-Ou-Mandel interferometer, resulting in a deterministically separated identical photon pair. The state is characterized by 92.9±0.9% visibility Hong-Ou-Mandel interference. The photon flux reaches ∼1.4×10(7) pairs nm-1 mW-1. The whole chip is designed to contain nine similar units to produce identical photon pairs spanning the telecom C and L band by the flexible engineering of nonlinearity. Our work presents a scenario for on-chip engineering of different photon sources and paves the way to fully integrated quantum technologies.

Reconfigurable Waveguide Filter with Variable Bandwidth and Center Frequency

This paper presents a center frequency and bandwidth reconfiguration mechanism for waveguide microwave bandpass filters. The filters are designed to be used in the output section of a satellite communication system. While the center frequency of a bandpass filter can be tuned by changing the lengths of the filter resonators, the coupling irises as practical realizations of the impedance inverters cannot easily be adapted to a new value. The novel approach chosen in this paper is to replace the impedance inverters by a novel type of coupling structure. This coupling structure allows adjustment of the coupling by changing the length of a transmission line, which is equivalent to changing the resonant frequency of a coupling resonator. Design equations are presented to transform an impedance inverter into the proposed coupling structure. A synthesis procedure for bandwidth reconfigurable filters is proposed. The feasibility of coupling adaptation is proven based on a full-wave model of the coupling structure. The synthesis process is applied to a four-pole Chebyshev sidewall-coupled circular waveguide filter with 54- and 72-MHz bandwidth settings. The filter is built up and measured. The measured results prove that the filter can be tuned to both bandwidths over a center frequency range of 200 MHz with excellent return loss and insertion loss.

Low SAR reconfigurable multiband planar inverted-F antenna for wireless communication applications

A low specific absorption rate (SAR) reconfigurable multiband coplanar waveguide fed planar inverted-F antenna (PIFA) is presented in this paper. Different numbers of meander-turn-shaped slots are etched on the PIFA radiating plate to excite new resonant frequencies. Extra resonant frequencies are created by increasing the number of meander-turn-shaped slots for different wireless communication applications. A new independent resonant frequency is created by etching a coupled slot within the ground plane for the upper WLAN. A PIN diode switch is used to reconfigure the fundamental resonant frequency from the LTE band 11 to band 8 with a total of 63% size reduction compared with the original PIFA size. Furthermore, the SAR in the human head is investigated using the Hugo voxel model in CST Microwave Studio. The volume of the antenna is 22 × 30 mm2over a 35 × 50 mm2ground plane, which is suitable for handheld devices.

On-chip quantum interference between silicon photon-pair sources

Large-scale integrated quantum photonic technologies will require the on-chip integration of identical photon sources with reconfigurable waveguide circuits. Relatively complex quantum circuits have already been demonstrated, but few studies acknowledge the pressing need to integrate photon sources and waveguide circuits together on-chip. A key step towards such large-scale quantum technologies is the integration of just two individual photon sources within a waveguide circuit, and the demonstration of high-visibility quantum interference between them. Here, we report a silicon-on-insulator device combining two four-wave mixing sources, in an interferometer with a reconfigurable phase shifter. We configure the device to create and manipulate two-colour (non-degenerate) or same-colour (degenerate), path-entangled or path-unentangled photon pairs. We observe up to 100.0+/-0.4% visibility quantum interference on-chip, and up to 95+/-4% off-chip. Our device removes the need for external photon sources, provides a path to increasing the complexity of quantum photonic circuits, and is a first step towards fully-integrated quantum technologies.