Crosstalk Reduction Research Articles

Anisotropic slot waveguides with bulk transition metal dichalcogenides for crosstalk reduction and high-efficiency mode conversion.

Conventional slot waveguides (CSWs) consisting of an isotropic low-index material sandwiched by two high-index silicon wires have been extensively used in functional photonic devices, including chemical sensing, optical modulating, and all-optical signal processing, due to its significantly enhanced electric field perpendicular to the interfaces in the slot layer. However, there are two drawbacks to be improved if the CSWs are used for signal transmission in photonic integrated circuits, including the crosstalk between waveguides and direct butting mode conversion efficiency (MCE) to a silicon (Si)-strip waveguide. In this study, we propose an anisotropic SW with bulk transition metal dichalcogenide (ASWTMD) to relieve the two shortcomings by replacing the isotropic low-index slot layer with a bulk molybdenum disulfide layer having a high refractive index and giant optical anisotropy. We demonstrated the crosstalk reduction (CR) of the proposed ASWTMD by analyzing the mode profile, power confinement, and coupling strength. We also investigated the MCE by examining the mode overlap ratio and power evolution. The proposed ASWTMD shows significant CR and superior MCE for the transverse electric and transverse magnetic modes compared to those of a CSW with a SiO2-slot layer. The present design paves the possible extensibility to other transition metal dichalcogenides (TMDs) for designing state-of-the-art TMD-based photonic devices exploiting their extraordinary optical properties.

Crosstalk reduction between microstrip lines using TL‐shaped defected microstrip structure

AbstractAiming at the problem of far‐end crosstalk between microstrip lines, a method to improve crosstalk by using the TL‐shaped defective microstrip structure (DMS) is proposed. This method optimizes the ratio of the capacitive coupling and the inductive coupling between coupled microstrip lines by etching TL‐shaped DMSs on the microstrip lines, reducing the strength of electromagnetic coupling, thereby achieving an improvement in crosstalk. The quantitative equivalent model, S‐parameters, and full‐wave EM simulations are used to analyze the frequency response of the TL‐shaped DMS and crosstalk between the microstrip lines. The results of High Frequency Structure Simulator software simulation and sample texts show that the TL‐shaped DMS can effectively improve the far‐end crosstalk while ensuring the transmission of signals on the microstrip line. In the frequency range of 0–8 GHz, the far‐end crosstalk can be improved by about 11 dB, and the maximum can be improved by 42 dB. Compared with other DMSs, the TL‐shaped DMS has better crosstalk improvement effect and practical application potential.

Near-IR absorption enhancement and crosstalk reduction of a photodiode in a CMOS indirect time-of-flight sensor.

The photodiode in a CMOS indirect time-of-flight (ITOF) sensor is a two-tap sensor especially designed for ranging. The three most important parameters are the demodulation contrast (DC), quantum efficiency (QE), and crosstalk. A trench nanostructure is commonly used as isolation layer between the pixels in a backside-illuminated CMOS sensor. In this paper, a trench is used to increase the IR absorption and decrease the crosstalk between pixels without a decrease in the DC. A trench grid is designed on top of a 6 µm thick silicon absorption layer to increase the optical path. A metal layer also is placed under the Si absorption layer as a reflection layer. The absorption of 940 nm infrared light can be increased up to 50%. The estimated QE can reach up to 40% at 940 nm. Deep trench isolation with a 6 µm depth is also used to isolate neighboring pixels. The crosstalk between the pixels can be reduced to less than 4% per neighboring pixel. This result shows a feasible CMOS ITOF sensor pixel design that we believe has great potential for use in solid-state lidar, depth cameras, machine vision, biomedical engineering, and facial recognition.

Comparison of Blind Source Separation Methods to Surface Electromyogram for Extensor Muscles of the Index and Little Fingers.

Crosstalk is the result of the propagation of muscle electrical signals on surface electromyogram channels simultaneously. The objective of this paper is to study the behavior of three blind source separation (BSS) methods for crosstalk reduction during finger extensor muscle contractions: FastICA, joint diagonalization of covariance matrices and optimal filtering. These methods have been tested on artificial mixtures defined by a temporal sum of the real signals from isolated contraction of two independent biomechanical muscles for the extension of the index and little finger. Artificial mixtures display a ground truth for comparison between the methods. The separation was better using the optimal filtering compared to the other two methods. The optimal filtering have then be tested on real mixtures recorded during a simultaneous contraction of the two muscles. The results are less satisfactory but open doors to new perspectives.

Design and Demonstration of a Novel Long-Range Photon-Counting 3D Imaging LiDAR with 32 × 32 Transceivers

Geiger-mode single-photon LiDAR is an important tool for long-distance three-dimensional remote sensing. A planar-array-based photon counting LiDAR that uses 32-by-32 fiber arrays coupled to an optical lens as a transceiver unit was developed. Using transmitters and receivers with the same design, the proposed device easily achieves a high-precision alignment of 1024 pixels and flexible detection field-of-view design. The LiDAR uses a set of relay lenses to couple echoes from the receiving fiber arrays to the pixels of a planar-array single-photon detector, which has a resolution enhanced by a factor of four (64-by-64) relative to the fiber array to reduce cross talk from neighboring pixels. The results of field experiments demonstrate that the proposed LiDAR can reconstruct a three-dimensional image from a distance of 1600 m. Even at an acquisition time of only 40 ms, targets with an area of approximately 50% can still be identified from 200 frames. These results demonstrate the potential of the LiDAR prototype for use in instantaneous high-density point-array measurement and long-range wide-FoV 3D imaging, which can be used in remote sensing applications such as airborne surveys and mapping. In the future, we will integrate the proposed LiDAR prototype and the pose measurement system to take the aircraft-based 3D imaging remote sensing experiments.

Crosstalk reduction in tabletop multiview display with fog screen

Fog screens offer a great advantage to be used as scattering screens in three-dimensional displays. In the absence of a fixed rigid form, fog screens work as screens without any physical obstruction. The density of water droplets can be regulated to adjust the screen's transparency and scattering level. This study proposes a method for crosstalk reduction between adjacent viewing windows by decreasing the divergence of view of the projector, with concentration lenses. By applying the Scheimpflug principle, we also reduce the keystone effect, which occurs when the fog screen is slanted with respect to the optical axis. In this study, we have realized a tabletop multiview fog display without any structures on the table and established that the proposed method is feasible for decreasing crosstalk effectively.

Broadband optical Ta2O5 antennas for directional emission of light.

Highly directive antennas with the ability of shaping radiation patterns in desired directions are essential for efficient on-chip optical communication with reduced cross talk. In this paper, we design and optimize three distinct broadband traveling-wave tantalum pentoxide antennas exhibiting highly directional characteristics. Our antennas contain a director and reflector deposited on a glass substrate, which are excited by a dipole emitter placed in the feed gap between the two elements. Full-wave simulations in conjunction with global optimization provide structures with an enhanced linear directivity as high as 119 radiating in the substrate. The high directivity is a result of the interplay between two dominant TE modes and the leaky modes present in the antenna director. Furthermore, these low-loss dielectric antennas exhibit a near-unity radiation efficiency at the operational wavelength of 780 nm and maintain a broad bandwidth. Our numerical results are in good agreement with experimental measurements from the optimized antennas fabricated using a two-step electron-beam lithography, revealing the highly directive nature of our structures. We envision that our antenna designs can be conveniently adapted to other dielectric materials and prove instrumental for inter-chip optical communications and other on-chip applications.

Cross-talk reduction in a graphene-based ultra-compact plasmonic encoder using an Au nano-ridge on a silicon substrate

Plasmonic waveguides have been widely studied in the rapid development of optically integrated circuits. The cross talk between plasmonic waveguides is a critical issue that should be considered. Nano-plasmonic waveguides with tunable graphene-free patterns on silicon ridge have very attractive features. Despite these attractive features, the low confinement in plasmonic waveguides reduces the coupling length. This issue results in high cross talk in optical integrated circuits. We present a solution to the mentioned problem. A metal ridge under the plasmonic channel helps to reduce the cross-talk value. A new graphene-based plasmonic waveguide has been proposed for achieving the switching operation at terahertz frequencies. Based on the designed waveguide, a 4-to-2 plasmonic encoder with the cross talk of -17.33dB has been presented. Using six waveguides, the encoder is designed with a contrast ratio of 14.44 dB and an area of 0.36µm2. Concerning the obtained results, the presented structure can be used in optical integrated circuits.

Double photon coincidence crosstalk reduction method for multi-nuclide Compton imaging

Compton imaging based on Compton scattering kinematics has the potential to visualize multi-nuclides by discriminating the total energy of Compton scattering and photoelectric absorption events. This feature enables us to perform multi-tracer imaging that reflects different functional information in nuclear medicine, resulting in a definitive diagnosis and being useful for biological and medical research. One of the challenges with multi-nuclide imaging is the crosstalk artifacts caused by scattered photons of higher energy gamma-rays. In this study, we investigated the potential benefits of the double photon coincidence detection as a drastic crosstalk reduction method. Coincidence detection of successive gamma-rays can differentiate nuclides and reduce the background caused by other nuclides' gamma-rays because some nuclides emit two or more gamma-rays in rapid succession. In this study, we focused on the coincidence detection of a Compton event and a photoelectric absorption event, and we showed simultaneous double photon emitter imaging of 111In and 177Lu with a ring-type Compton imaging system. The artifacts caused by other nuclides' gamma-rays were reduced by extracting Compton events coincident with photoelectric absorption events. The coincidence Compton images demonstrated a signal-to-background ratio improvement of 1.1–1.7 times over the one of no-coincidence Compton images, despite a drop in intrinsic detection efficiency of the order of 10-2. This strategy of directly reducing crosstalk will be useful in other combinations imaging such as of 111In (or 177Lu) and a positron emission tomography nuclide.

Impedance and Dielectric Properties of PVC:NH4I Solid Polymer Electrolytes (SPEs): Steps toward the Fabrication of SPEs with High Resistivity.

In the present article, a simple technique is provided for the fabrication of a polymer electrolyte system composed of polyvinyl chloride (PVC) and doped with varying content of ammonium iodide (NH4I) salt using solution-casting methodology. The influences of NH4I on the structural, electrochemical, and electrical properties of PVC have been investigated using X-ray diffraction, electrochemical impedance spectroscopy (EIS), and dielectric properties. The X-ray study reveals the amorphous nature of the polymer–salt complex. The EIS measurement revealed an ionic conductivity of 5.57 × 10−10 S/cm for the electrolyte containing 10 wt.% of salt. Our hypothesis is provided, which demonstrated the likelihood of designing highly resistive solid electrolytes using the concept of a polymer electrolyte. Here, the results showed that the resistivity of the studied samples is not dramatically decreased with increasing NH4I. Bode plots distinguish the decrease in resistance or impedance with increasing salt contents. Dielectric measurements revealed a decrease in the dielectric constant with the increase of NH4I content in the PVC polymer. The relaxation time and dielectric properties of the electrolytes confirmed their non-Debye type behavior. This pattern has been validated by the existence of an incomplete semicircle in the Argand plot. Insulation materials with low εr have found widespread applications in electronic devices due to the reduction in delay, power dissipation, and crosstalk. In addition, an investigation of real and imaginary parts of electric modulus leads to the minimized electrode polarization being reached.

High-fidelity CNOT gate for spin qubits with asymmetric driving using virtual gates

Recent experiments have demonstrated two-qubit fidelities above 99%, however, theoretically, the fidelity of CNOT operations is limited by off-resonant driving described by off-diagonal terms in the system Hamiltonian. Here we investigate these off-diagonal contributions and we propose a fidelity improvement of several orders of magnitude by using asymmetric driving. Therefore, we provide a description of an ac virtual gate based on a simple capacitance model which not only enables a high fidelity CNOT but also crosstalk reduction when scaling up spin qubit devices to larger arrays.

Study and Analysis of Crosstalk Reduction in UAV Cabling by Using Various Cable Types

Study and Analysis of Crosstalk Reduction in UAV Cabling by Using Various Cable Types

Multimode fiber as a tool to reduce cross talk in Fourier-domain full-field optical coherence tomography.

Fourier-domain full-field optical coherence tomography (FD-FF-OCT) is an emerging tool for high-speed eye imaging. However, cross-talk formation in images limits the imaging depth. To this end, we have recently shown that reducing spatial coherence with a fast deformable membrane can suppress the noise but over a limited axial range and with substantial data processing. Here, we demonstrate that a multimode fiber with carefully chosen parameters enables cross-talk-free imaging over a long axial range and without significant artifacts. We also show that it can be used to image the human retina and choroid in vivo with exceptional contrast.

Design of a CMOS image sensor pixel with embedded polysilicon nano-grating for near-infrared imaging enhancement.

Complementary metal-oxide semiconductor (CMOS) image sensor sensitivity in the near-infrared spectrum is limited by the absorption length in silicon. To deal with that limitation, we evaluate the implementation of a polysilicon nano-grating inside a pixel, at the transistor gate level of a 90 nm standard CMOS process, through opto-electrical simulations. The studied pixel structure involves a polysilicon nano-grating, designed with the fabrication layer of the transistor gate, which does not require any modifications in the process flow. The diffraction effect of the nano-grating increases the length of the light path in the photosensitive area and thus increases the photoelectric conversion efficiency. The nano-grating is integrated in combination with deep trench isolations to reduce cross talk between pixels. Coupled optical and electrical simulations report 33% external quantum efficiency improvement and 7% cross talk reduction at 850 nm.

A 4 × 10 Gb/s Adaptive Optical Receiver Utilizing Current-Reuse and Crosstalk-Remove

This article presents a $4 \times 10$ Gb/s low-noise adaptive optical receiver, utilizing a current-reuse architecture and channel crosstalk-remove techniques in 65-nm CMOS process. The receiver integrates a transimpedance amplifier (TIA), a continuous-time linear equalizer (EQ), high-gain and high-bandwidth limiting amplifiers, and a 50- $\Omega $ output driver into a single die. The TIA employs a common-source-based pseudo-differential topology with input series inductive peaking and $g_{m}$ -enhancement to improve bandwidth and noise performance. An automatic-gain-control loop scheme is presented which solves the bandwidth variation issue caused by variation of the TIA input impedance, across a large dynamic range of a small input to a maximum overload current. Multiple crosstalk reduction techniques are adopted to improve the channel isolation performance. The 850-nm vertical cavity surface emitting laser (VCSEL)-based full-link measurement results show that the optical receiver achieves $20.4~\mu \text{A}_{\mathrm {pp}}$ sensitivity bit-error-rate (BER $ -12) with a 200-fF photodiode, competitive with other prior CMOS-based TIAs. The crosstalk over different channels is also measured, demonstrating only a sensitivity penalty of 1 dB.

Crosstalk reduction in a piezoelectric phononic plate induced by electrical boundary conditions: Application to multi-element transducers

This paper proposes a method of passive electrical decoupling which aimed at found application in reducing the crosstalk phenomenon in multi-element ultrasonic transducers. A homogeneous piezoelectric plate, covered on one side by a 1D periodic arrangement of thin metallic electrodes and on the other side by a full electrode, is considered. Finite element analysis and experimental measurements are performed to obtain the dispersion curves and normal displacements at the surface of the structure. It is shown that applying inductive shunts at the electrodes, band gaps can be created in the first Brillouin zone, which can prevent from the establishment of the first thickness mode in the plate. In that way the mechanical inter-element coupling can be lowered. Thus, the acoustic radiation in water from one sector excited at the resonance frequency is found to be closer to that of a piston mode. The transposition of this principle to the situation of a transducer including a rear medium and a front matching layer confirms the possibility of reducing the inter-element coupling. However, the physical effects at the origin of this reduction are different from those inherent to the cutting of a piezocomposite ceramic as it is done in most probes available in the market. As a result, we show that taking advantage of the electrical boundary conditions upon the passive elements in a transducer gives real opportunities for crosstalk reduction that may be implemented in ultrasonic systems for imaging in the medical field and in NDT.

Reduction in Crosstalk Using Uniform Germanium Strips for Dense Integration of Photonic Waveguides

The requirement of low crosstalk between the neighboring waveguides should be considered essentially, in order to achieve the compact photonic integrated circuit (PIC), which includes photonic waveguides. Literature shows that the lower crosstalk can be realized by using the silicon-on-insulator (SOI) based waveguide, having an appropriate separation between them. The current work is focused on reducing the waveguide separation to further improve the photonic integration over the PICs. This has been achieved by inserting the germanium strips between the photonic waveguides. The investigations of the impact of variations in heights and widths of germanium strip have demonstrated that the crosstalk can be reduced by a significant amount, which provides noteworthy improvement in coupling length. The maximum coupling lengths of 81,578 μm, 67,099 μm, and 66,810 μm have been achieved at their respective end-to-end separations of 300 nm, 250 nm, and 200 nm, and their corresponding minimum crosstalk values have been noted as −29.40 dB, −27.71 dB, and − 27.70 dB. Moreover, the analysis to realize the coupling length for Ge-strip, have been compared with the Si-, and Si3N4-strips. The approach presented in the current work can be utilized for the design of many compact photonic applications, such as polarization splitter, integrated photonic switches, etc.

Crosstalk reduction using novel cross-shaped resonators with via fence in high-frequency transmission lines

PurposeThe purpose of this paper is to design a suitable guard trace to reduce the electromagentic interference between two closely spaced high frequency transmission lines. A novel cross-shaped resonator combined via fence is passed down to alleviate far-end and near-end crosstalk (NEXT) in tightly coupled high-speed transmission lines. The distance between the adjacent transmission lines is increased stepwise as a function of trace width.Design/methodology/approachA rectangular-shaped resonator via fence is connected by a guard trace has been proposed to overcome the coupling between the traces that is separated by 2 W. Similarly, by creating a cross-shaped resonator via fence connected by guard trace that reduces the spacing further by 1.5 W.FindingsA tightly coupled transmission line structure that needs separation by a designed unit cell structure. Further research needs to be conducted to improve the NEXT, far-end crosstalk (FEXT) and spacing between the transmission lines.Originality/valueThis study portrays a novel method that combines the resonators via fence with a minimum spacing between the tightly coupled transmission lines which reduce the NEXT and FEXT; thereby reducing the size of the routing area. The resultant test structures are characterized at high frequencies using time domain and frequency domain analysis. The following scattering parameters such as insertion loss, NEXT and FEXT of the proposed method are measured as 1.504 dB, >30 dB and >20 dB, respectively.

Polarization Selective Transparent Electrode With Patterned Metal for the 3D Display Pixel

We propose a polarization selective transparent electrode (PSTE) utilizing a rectangular-shaped metal nano-wire structure. The performance of the PSTE was evaluated with simulation based on finite element method (COMSOL Multiphysics). Parametric studies have been carried out to give a guide for geometric parameter selection to meet the requirement of the target application. According to the studies, 70 nm by 800 nm rectangular metal grid, having a thickness of 100 nm and linewidth of 30 nm were recommended to keep higher than 61% transmittance, 24 dB extinction ratio, and lower than 5 Ω/sq sheet resistance. As an application of PSTE, a design idea about crosstalk reduction of the passive stereoscopic 3D display is proposed by presenting its pixel structure employing the proposed PSTE. The light extraction efficiency of the proposed pixel employing PSTE structure was also evaluated and compared to the structure employing the lossless ITO (Indium Tin Oxide), by measuring extracted light output power from incoherently distributed dipole sources excited in the emission layer. Degradation of the extraction efficiency below 14 percent point was expected compared to the lossless ITO for all the primary color wavelength range.

Recoverable and rewritable waveguide beam splitters fabricated by tailored femtosecond laser writing of lithium tantalate crystal

We report on an integrated 1 × 5 beam splitter based on optical waveguides with type I and type II modifications of femtosecond laser (fs-laser) writing in lithium tantalate (LiTaO3) crystal. The cladding waveguides consisting of type-II modified tracks are used for optical signal transmission, photon crosstalk reduction, and mode field regulation. The single-line waveguides with type I modification are utilized for light beam splitting. Type-I single-line waveguides are with relatively weak thermal stability, which are utilized to produce a recoverable and rewritable optical beam splitter, and the structure still possesses good transmission properties after the reconstruction. Especially, the type-I modified waveguides can be rewritten in very short time (1–2 min). The beam splitter shows good performance in outputting programmable optical signals, which provides a possible strategy for the development of erasable photonic data processors.