On-chip Communication System Research Articles

Compact and low-crosstalk multimode waveguide crossing utilizing subwavelength holey metamaterial waveguides

To further increase the transmission capacity of on-chip optical communication systems, hybrid division multiplexing technology has emerged as a crucial alternative solution, in which multimode waveguide crossings are highly desired. In this paper, we propose and experimentally demonstrate a compact multimode (i.e., three different modes) waveguide crossing that employs subwavelength holey metamaterial waveguides (SHMWs). The used SHMW, formed by inserting subwavelength periodic holes into a multimode interference (MMI) coupler, deservedly exhibits synergetic advantages of the two kinds of structures, enabling an attractive three-mode (e.g., TE0, TM0, and TM1) waveguide crossing with flexible design, small size, and good performance. Simulation results show that the realized device has a low insertion loss (< 0.74 dB), low reflection loss (<−13.1 dB), and low crosstalk (<−31.6 dB) at a central wavelength of 1550 nm for all the modes with a compact footprint of 27.4 µm × 27.4 µm. The experimental results prove that insertion losses are as low as 0.72 dB, 0.27 dB, and 0.90 dB for TE0, TM0, and TM1 mode, respectively, with the corresponding crosstalk below −38 dB at 1550 nm. The proposed device can be widely applied in photonic integrated circuits to construct photonic systems with the abilities of mode control and multiplexing.

Enhancing Security in On-Chip Communication: A Survey of Threats and Solutions

As the complexity of integrated circuits (ICs) continues to increase, ensuring the security of on-chip communication becomes paramount. With the rise of interconnected devices and the Internet of Things (IoT), vulnerabilities in on-chip communication pose significant risks to data integrity, privacy, and system reliability. This article presents a comprehensive survey of the threats and solutions associated with enhancing security in on-chip communication. The survey begins with an overview of on-chip communication and its critical role in modern ICs. It then explores the diverse range of security threats faced by on-chip communication systems, including side-channel attacks, information leakage, unauthorized access, and the insertion of hardware Trojans. Each threat is examined in detail, highlighting its characteristics and potential impact on system security. In response to these threats, the survey examines various solutions and countermeasures aimed at enhancing on-chip communication security. These include encryption and authentication techniques, secure routing protocols, hardware-based security mechanisms, and software-based security solutions. Examples of real-world security breaches and successful implementations of security solutions are also presented to provide practical insights.

Multichannel direct communication based on a programmable topological plasmonic metasurface

With the gradual improvement of the future wireless communication technology, the demand for high information capacity and reliable links in communication systems is also ever-increasing. Programmable topological plasmonic metasurfaces, consisting of artificially engineered structures with robust propagation pathways control, have emerged as a revolutionary technology for stable microwave and on-chip communication systems. Programmable topological plasmonic metasurfaces offer unprecedented flexibility and adaptability in managing multiple communication channels as the propagation paths can be easily reconfigured to meet specific communication requirements. Here, we have experimentally demonstrated the ability to dynamically manipulate electromagnetic waves along eight distinct topological pathways for a multichannel direct communication system. The simulation results of topological plasmonic metasurfaces with different coding schemes have showcased their excellent performance in multichannel wavefront control. Experimental results have consistently aligned with the simulation findings, validating the effectiveness of multichannel topological routes. Furthermore, an eight-channel direct communication system based on a programmable topological plasmonic metasurface is designed and implemented to transmit different information. The proposed multichannel communication system based on a programmable topological plasmonic metasurface opens up new possibilities for high-capacity, efficient, and adaptive communication systems, which hold great potential in transformative applications in areas such as 6G, Internet of Things, and beyond.

Solar-blind photonic integrated chips for real-time on-chip communication

The monolithically integrated self-driven photoelectric detector (PD) with the light-emitting diode (LED) epitaxial structure completely relies on the built-in electric field in the multi-quantum wells region to separate the photogenerated carriers. Here, we propose a novel superlattices–electron barrier layer structure to expand the potential field region and enhance the detection capability of the integrated PD. The PD exhibits a record-breaking photo-to-dark current ratio of 5.14 × 107, responsivity of 110.3 A/W, and specific detectivity of 2.2 × 1013 Jones at 0 V bias, respectively. A clear open-eyed diagram of the monolithically integrated chip, including the PD, LED, and waveguide, is realized under a high-speed communication rate of 150 Mbps. The obtained transient response (rise/decay) time of 2.16/2.28 ns also illustrates the outstanding transient response capability of the integrated chip. The on-chip optical communication system is built to achieve the practical video signals transmission application, which is a formidable contender for the core module of future large-scale photonic integrated circuits.

Terahertz plasmonic functional devices enabled by multimode interference

Terahertz integrated devices have attracted great attention due to their potential applications in communication systems. Although some functional devices based on terahertz spoof surface plasmon polariton (SPP) waveguides have been studied, multimode waveguides and multimode interference mechanism have rarely been explored. This work investigates several key functional plasmonic devices based on multi-SPP mode interference in the terahertz regime. The feasibility of multimode transmission on terahertz plasmonic waveguides and control of the propagation modes by varying the waveguide parameters are first investigated. Then, the interference mechanism between two or more propagation modes and the self-imaging principle are applied to plasmonic waveguides. Finally, a series of terahertz plasmonic functional devices such as a coupler, wavelength diplexers, and cascaded devices are proposed and simulated by exploring different interference lengths, frequencies, and cascades via the self-imaging principle. These devices have good performance in transmission response, crosstalk, bandwidth, and footprint, and are expected to play an important role in the development of terahertz on-chip communication systems.

Coexistence of large-area topological pseudospin and valley states in a tri-band heterostructure system.

The rapid development of topological photonics has significantly revolutionized our comprehension of electromagnetic wave manipulation in recent decades. Recent research exploiting large-area topological states inserts an additional gapless PC structure between topologically trivial and nontrivial PCs, effectively introducing the mode width degree of freedom. Nevertheless, these heterostructures mainly support only single-type waveguide states operating within a single frequency band. To address these limitations, we propose a novel, to the best of our knowledge, tri-band three-layer heterostructure system, supporting both large-area pseudospin- and valley-locked states. The system showcases tunable mode widths with different operational bandwidths. Moreover, the heterostructures exhibit inherent topological characteristics and reflection-free interfacing, which are verified in the well-designed Z-shaped channels. The proposed heterostructure system can be used to design multi-band multi-functional high-flexibility topological devices, providing great advantages for enlarging the on-chip integrated communication systems.

An Integrated Pump-Controlled Variable Coupler Fabricated by Ultrafast Laser Writing.

The design and fabrication of a integrated symmetric directional coupler dependent o the pumping power and operating at a 1534 nm wavelength is reported. The twin-core waveguide was inscribed into Er3+/Yb3+ co-doped phosphate glass by a femtosecond laser direct writing technique. By optical pumping, the coupling ratio can be modulated due to the changes induced in the refractive index of the material. The experimental results demonstrated that the coupling ratio can be tuned continuously from 100/0 to 50/50 by increasing the pump's power from 0 to 350 mW. The developed twin-core coupler has promising applications for on-chip all-optical signal processing and communication systems.

Ultracompact terahertz plasmonic mode division multiplexer.

In this Letter, an ultracompact terahertz (THz) mode division multiplexer based on THz spoof surface plasmon polaritons (SPPs) is proposed. Compared with traditional optical multiplexing devices, the proposed mode multiplexer can be designed with a reduced footprint by exploiting more degrees of freedom in the parameters of the unit cell, namely a rectangular metallic pillar. The ultracompact mode division multiplexer can simultaneously support the propagation of four mode channels: the TM0, TM1, TM2, and TM3 modes. Then, we numerically evaluate the performance of a cascaded plasmonic mode division circuit composed of a mode multiplexer and demultiplexer. The cross talk and excess loss of the whole circuit are lower than -15 dB and 3.7 dB, respectively, for all four mode channels at a center frequency of 0.65 THz. The footprint of the whole device is about 27 × 2.3 mm and the length of each coupling region is about 2.7 mm. For the first time, to the best of our knowledge, a mode division multiplexer based on THz spoof SPPs is reported, which will form core devices for future THz on-chip multimode communication systems.

Importance Sampling Over Monte Carlo Technique to Estimate Wireless Infrared On-Chip Communication

Optical code division multiple access (OCDMA) represents the development of optical communication. The advantages of OCDMA such as, asynchronous multiuser communication transmission, flexibility, ample bandwidth and scalability; have made this technique a better candidate to be proposed for next generation network on chip. In this paper, performance of on-chip OCDMA communication system is analyzed. Analytical techniques for estimating the performance of optical communication systems are difficult, complicated and no complete analytical treatment of the problem has been obtained before. Simulation techniques such as Monte Carlo (MC) are used to obtain reasonable estimates of these systems performance. For optical communications, Monte Carlo require excessively large sample sizes which makes it cumbersome in terms of physical resources, and are not practical for estimating very low values of error probabilities. Modified Monte-Carlo (Importance sampling/IS) method was used to reduce the number of simulation tests for estimating error probabilities for optical communications systems by modifying the probability density function of the on-chip noise process. Simulation results are presented and assessed in term of bit error rate (BER), showing the contribution of IS relatively to MC.

Dynamic Tunable Meta-Lens Based on a Single-Layer Metal Microstructure

Ultra-thin focusing meta-lenses based on the metasurface structure with adjustable focal length show important applicant value in compact systems, especially in on-chip terahertz spectroscopy, imaging systems, and communication systems. A stretchable substrate, dynamic focusing meta-lens based on the cross-polarized metal C-shaped split ring resonators (SRRs) is designed and investigated. At the operation frequency of 0.1 THz, the operation characteristics of the unit cell structure and the formed meta-lens are investigated. The phase of the unit cell structures can be modulated by changing the rotation angle, width, and symmetry axis of the C-shaped metal SRRs. When the terahertz wave is incident vertically, the focusing performance can be achieved based on the specific arrangement of the metasurface unit cells. By stretching the flexible substrate of the meta-lens, the dynamic focusing effect can be realized. When the substrate stretches from 100% to 120%, the focal length changes from 59.8 mm to 125.2 mm, the dynamic focusing range is 109.4% of the minimum focal length, and the focusing efficiency changes between 5.5% and 10.5%.

Experiment demonstration of high speed 1.3 µm grating assisted surface-emitting DFB lasers.

Surface emitting lasers are attractive light sources for silicon integrated photonic circuits. High speed direct operation is of great importance for these lasers in high capacity and low cost on-chip communication system. Here, we demonstrate a 1.3 µm surface emitting ridge-waveguide distributed feedback (DFB) laser with second order grating and λ/4 phase shift grating, which can achieve a 24 Gb/s operation over a wide temperature. The fabricated lasers can achieve low threshold current as 6.8 mA, and 12.5 mA at 20, and 70°C, respectively. Stable single mode operation has been observed with high side mode suppression ratio (SMSR) > 40 dB at all temperatures (20-70 °C). Meanwhile, the surface emitting optical power can reach 1.7 mW at high temperature as 70 °C. 3 dB bandwidth of small signal response is 21 GHz and 12 GHz at 20 °C and 70 °C respectively. The far-field divergence angle of surface emitting beam is 13.4°×20.2° of 10 µm length second order grating coupler. The proposed laser may have great advantages of single mode, high speed modulation and good temperature tolerance. In addition, compared with conventional DFB lasers, the surface emitting DFB laser has no additional manufacturing process, which is simple to fabricate and easy to integrate with silicon platform.

Ultrafast dynamic switching of optical response based on nonlinear hyperbolic metamaterial platform

The pursuit of high-speed and on-chip optical communication systems has promoted extensive exploration of all-optical control of light-matter interactions via nonlinear optical processes. Here, we have numerically investigated the ultrafast dynamic switching of optical response using tunable hyperbolic metamaterial (HMM) which consists of five pairs of alternating layers of indium tin oxide (ITO) and SiO2. The nonlinearity of the HMM is analyzed by the ultrafast dynamics of the hot electrons in the epsilon-near-zero (ENZ) ITO. Our approach allows large and broad all-optical modulation of the effective permittivity and topology of the HMM on the femtosecond time-scale. Based on the proposed HMM platform, we have shown considerable tunability in the extinction ratio and Purcell enhancement under various pump fluence. In addition, we have achieved all-optical control of the coupling strength through depositing plasmonic resonators on the HMM platform. A significant tuning of the coupled resonance is observed by changing pump fluence, which leads to a switching time within 213 fs at a specific wavelength with a relative modulation depth more than 15 dB.

Gyrator-C-Based CMOS Active Inductors: Analysis of Performance Optimization Techniques

Inductors are critical components in RF applications, such as filters, oscillators, and amplifiers. However, integrated spiral inductors on silicon (Si) have shown performance limitations. They do not meet the challenges of current trends toward miniaturized, low-cost, and on-chip multistandard communication systems [1]. While they have good performance in terms of noise, linearity, and power consumption, as they do not need a dc bias to work, electromagnetic interference with neighboring circuitry is a major problem associated with the layout of spiral inductors.

Dynamic configurational anisotropy in Ni80Fe20 antidot lattice with complex geometry

Efficient tunability of spin-wave dynamics has been demonstrated in Ni80Fe20 diamond-shaped antidot lattices (DADLs) arranged in square and hexagonal symmetry using all-optical time-resolved magneto-optical Kerr effect (TRMOKE) microscope. A stark variation in the spin-wave spectra is obtained with the strength and orientation of the in-plane bias magnetic field. The spin-wave modes in the square lattice exhibit four-fold rotational anisotropy, which is in contrast to a strong six-fold rotational anisotropy superposed with a weak four-fold anisotropy observed in the hexagonal lattice. Micromagnetic simulations qualitatively reproduce the experimentally observed spin-wave modes and the simulated mode profiles reveal the presence of diverse genres of extended, pseudo extended and quantized standing spin-wave modes in these lattices. Additionally, some lower frequency localized edge modes are obtained for some specific bias field orientations due to the presence of demagnetizing fields at the sharp corners of the diamond antidots. The strong modifications of the demagnetizing regions, as well as the internal field strengths around the diamond-shaped antidots, can explain the observed variation of the spin-wave dynamics. These findings are important for potential applications of the DADLs in future magnonic devices, leading towards the development of on-chip microwave logic and communication systems.

Design of a high speed router for NOC

The complexity of System on Chip (SoC) is increasing with the scale of ICs, and Network on Chip (NoC) has become one of the most important solutions for SoC communication. As a significant point of NoC, research of routers and routing algorithms is receiving more and more attention from researchers and research institutes. This paper proposes a high-speed router on-chip router, which adopts wormhole switching mechanism, output queuing caching strategy, Credit-based flow control mechanism and Round-Robin arbitration mechanism, and the entire operation of the router is a two-stage flow. The selection of adaptive and deterministic routing algorithms can be done automatically, and finally, the performance parameters are evaluated.

Electrically connected spin-torque oscillators array for 2.4\u2009GHz WiFi band transmission and energy harvesting

The mutual synchronization of spin-torque oscillators (STOs) is critical for communication, energy harvesting and neuromorphic applications. Short range magnetic coupling-based synchronization has spatial restrictions (few µm), whereas the long-range electrical synchronization using vortex STOs has limited frequency responses in hundreds MHz (<500 MHz), restricting them for on-chip GHz-range applications. Here, we demonstrate electrical synchronization of four non-vortex uniformly-magnetized STOs using a single common current source in both parallel and series configurations at 2.4 GHz band, resolving the frequency-area quandary for designing STO based on-chip communication systems. Under injection locking, synchronized STOs demonstrate an excellent time-domain stability and substantially improved phase noise performance. By integrating the electrically connected eight STOs, we demonstrate the battery-free energy-harvesting system by utilizing the wireless radio-frequency energy to power electronic devices such as LEDs. Our results highlight the significance of electrical topology (series vs. parallel) while designing an on-chip STOs system.

VCS: A method of in-order packet delivery for adaptive NoC routing

Adaptive routing proves its efficiency in sustaining higher network performance bypassing packets through alternate congestion-free minimal or non-minimal routes for a many-core on-chip communication system. It prevents the network from reaching an early saturation due to the stalling of packets in the priority-fixed shortest route for a longer period. However, routing packets adaptively to an alternate route instead of choosing the priority-fixed and shortest route may lead to an unintended state of delivering packets out-of-order sequence at the destination node that is not accepted by many message-passing systems. This ordering mismatch is due to allowing multiple alternate routes for packets of the same communication flow in adaptive mode. In such a case, a packet with a higher sequence number takes over another packet of the same communication flow having a lower sequence number. Storing and reordering all unordered packets of the same communication flow at the sink side becomes costlier due to the increasing area and power requirement. Ideally, the added memory size reaches to infinity for storing all unordered packets that belong to the same communication flow. In the proposed method, we guarantee delivery of all packets belongs to the same communication flow in an orderly manner under adaptive routing mode. In particular, we have proposed a flow-control policy based on a virtual circuit switch (VCS) method that exclusively won and reserve a virtual path for routing packets in an adaptive mode for each communication flow. To maximize network performance, we allow sharing of the reserved path among packets of different communication flows, routing under priority fix deterministic mode. The method saves need of having additional memory unit for storing all unordered packets while guaranteeing the packet’s ordering sequence at the destination end. An experiment conducted on two different size Mesh networks (8x8 and 12x12) under several synthetic traffic and benchmark application reveals that our virtual circuit switching (VCS) based proposed method offers a significant improvement over the state-of-the-art packet reordering method (ROR) and two similar type of research works. Our simulation based experimental result shows that method offers a 60% higher saturation point and 21% improvements (maximum) in throughput while offering a reduction of 60% in NoC area and 58% power value compared to the baseline reorder (ROR) method.

Autonomous growth of NbN nanostructures on atomically flat AlN surfaces

Integrating the functions of superconductors and semiconductors by epitaxial growth can lead to the fabrication of quantum devices such as on-chip quantum communication systems with single-photon emitters and detectors. Furthermore, a combination of nitride superconductors and nitride semiconductors is one of the most suitable candidates for application in these quantum devices. However, the structure of superconducting NbN films grown on nitride semiconductors needs to be elucidated. In this study, we report the self-organization of NbN nanostructures that were epitaxially grown on an atomically flat AlN surface. Structural investigation of the NbN/AlN heterostructure revealed that the growth of NbN twins on the AlN surface leads to the autonomous formation of nanostructures. These results significantly contribute to the materials science of cubic transition metal nitride heteroepitaxy.

Exploiting Data Resilience in Wireless Network-on-chip Architectures

The emerging wireless Network-on-Chip (WiNoC) architectures are a viable solution for addressing the scalability limitations of manycore architectures in which multi-hop long-range communications strongly impact both the performance and energy figures of the system. The energy consumption of wired links as well as that of radio communications account for a relevant fraction of the overall energy budget. In this article, we extend the approximate computing paradigm to the case of the on-chip communication system in manycore architectures. We present techniques, circuitries, and programming interfaces aimed at reducing the energy consumption of a WiNoC by exploiting the trade-off energy saving vs. application output degradation. The proposed platform—namely, xWiNoC—uses variable voltage swing links and tunable transmitting power wireless interfaces along with a programming interface that allows the programmer to specify those data structures that are error-resilient. Thus, communications induced by the access to such error-resilient data structures are carried out by using links and radio channels that are configured to work in a low energy mode, albeit by exposing a higher bit error rate. xWiNoC is assessed on a set of applications belonging to different domains in which the trade-off energy vs. performance vs. application result quality is discussed. We found that up to 50% of communication energy saving can be obtained with a negligible impact on the application output quality and 3% in application performance degradation.

Resilient System-on-Chip Designs With NoC Fabrics

Modern System-on-Chip (SoC) designs integrate a number of third party IPs (3PIPs) that coordinate and communicate through a Network-on-Chip (NoC) fabric to realize system functionality. An important class of SoC security attack involves a rogue IP tampering with the inter-IP communication. These attacks include message snoop, message mutation, message misdirection, IP masquerade, and message flooding. Static IP-level trust verification cannot protect against these SoC-level attacks. In this paper, we analyze the vulnerabilities of system level communication among IPs and develop a novel SoC security architecture that provides system resilience against exploitation by untrusted 3PIPs integrated over an NoC fabric. We show how to address the problem through a collection of fine-grained SoC security policies that enable on-the-fly monitoring and control of appropriate security-relevant events. Our approach, for the first time to our knowledge, provides an architecture-level solution for trusted SoC communication through run-time resilience in the presence of untrusted IPs. We demonstrate viability of our approach on a realistic SoC design through a series of attack models and show that our architecture incurs minimal to modest overhead in area, power, and system latency.