High-speed Information Processing Research Articles

Nonreciprocal spin wave channeling in ferromagnetic/heavy-metal nanostrips

Nonreciprocity, unidirectionality, and channeling are essential concepts for potential magnonic applications. Nonreciprocity and unidirectionality ensure the efficient propagation of spin waves along predetermined paths with preferential directions, disrupting the symmetry of counterpropagating waves. Channeling fosters the development of intricate spin-wave networks, enabling more sophisticated functionalities. Integrating these concepts into practical applications will shape the future of spin-wave-based information processing devices. This article theoretically studies the dynamics of spin waves in a ferromagnetic strip coupled to a heavy-metal strip, where the nonreciprocity, unidirectionality, and channeling effects are analyzed. Both backward volume (BV) and Damon–Eshbach (DE) configurations are considered, where the lateral dimensions of the heavy-metal and ferromagnetic strips can differ. Calculations show notable nonreciprocal channeling of spin waves in both DE and BV modes. In the BV configuration, the dispersion is reciprocal with nontrivial localization of lateral confined modes. It is shown that the waves can be channeled into the zones in contact with the HM, where the Dzyaloshinskii–Moriya interaction is active. In the DE configuration, the waves exhibit nonreciprocal spin-wave dispersion, allowing unidirectional and channeled spin-wave propagation. The main results are compared to micromagnetic simulations, where an excellent agreement between both methods is obtained. These findings are relevant for envisioning advanced magnonic devices, enabling precise control over spin-wave propagation for innovative, low-power, high-speed information processing.

Hanbury Brown and Twiss-type optical secret sharing

Towards growing challenges of information security and authentication, various optical techniques based on holography, diffraction, interference, metasurfaces, etc., deliver promising solutions with low energy consumption and parallel high-speed information processing. Here, we report on a new dimension–second-order coherence found in the well-known Hanbury Brown and Twiss (HBT) effect–for performing optical authentication and secret sharing. We develop a method to generate a pair of correlated phase-only masks, each of which is distributed to a shareholder and can produce a specific pattern as authentication under coherent illumination, while two secret images are encrypted in the mutual information of two masks. By combining two masks in two configurations, two secret images can be extracted through spatially cascaded display under coherent illumination and intensity correlation under incoherent illumination, respectively. Conspicuously, two extremes of coherence–spatially coherent or incoherent–will enable the encoding and decoding of two different images with the same phase masks, indicating that the first-order and second-order coherence can be two independent channels for optical cryptography just like other degrees of freedom of light (e.g., polarization). Moreover, we demonstrate a polarization-multiplexing scheme to achieve polarization-selective HBT-type optically secret-sharing with increased capacity, and this type of polarization-phase masks can be readily replaced with metasurfaces.

Leveraging multiplexed metasurfaces for multi-task learning with all-optical diffractive processors

Abstract Diffractive Neural Networks (DNNs) leverage the power of light to enhance computational performance in machine learning, offering a pathway to high-speed, low-energy, and large-scale neural information processing. However, most existing DNN architectures are optimized for single tasks and thus lack the flexibility required for the simultaneous execution of multiple tasks within a unified artificial intelligence platform. In this work, we utilize the polarization and wavelength degrees of freedom of light to achieve optical multi-task identification using the MNIST, FMNIST, and KMNIST datasets. Employing bilayer cascaded metasurfaces, we construct dual-channel DNNs capable of simultaneously classifying two tasks, using polarization and wavelength multiplexing schemes through a meta-atom library. Numerical evaluations demonstrate performance accuracies comparable to those of individually trained single-channel, single-task DNNs. Extending this approach to three-task parallel recognition reveals an expected performance decline yet maintains satisfactory classification accuracies of greater than 80 % for all tasks. We further introduce a novel end-to-end joint optimization framework to redesign the three-task classifier, demonstrating substantial improvements over the meta-atom library design and offering the potential for future multi-channel DNN designs. Our study could pave the way for the development of ultrathin, high-speed, and high-throughput optical neural computing systems.

Bionic firing activities in a dual mem-elements based CNN cell

Firing activities provide the potential possibility for achieving bio-brain functionality with high energy-efficient and high-speed information processing performance. This inspires the design of bionic circuits to generate firing activities and develop brain-like applications. In this paper, a dual mem-elements based cellular neural network (CNN) cell is constructed to produce bionic firing activities, in which a non-ideal memcapacitor and an N-type locally active memristor are employed to emulate the functions of the neuronal membrane. The proposed CNN cell has an excitation-dependent equilibrium trajectory and stability. Numerical analysis shows that the dual mem-elements based CNN cell has abundant dynamical behaviors of forward/reverse period-doubling bifurcation routes, chaos crisis, tangent bifurcation, and bubbles with the change of model parameters of the CNN cell, memcapacitor, and exciting source. As a result, the rich firing patterns’ transition can be observed from the two-dimensional dynamics evolution. The analog circuit of the proposed CNN cell is designed, and then a PCB-based hardware circuit is implemented. The experimental results certify the accuracy of the theoretical and numerical analysis.

Generation of multi-photon Fock states at telecommunication wavelength using picosecond pulsed light.

Multi-photon Fock states have diverse applications such as optical quantum information processing. For the implementation of quantum information processing, Fock states should be generated within the telecommunication wavelength band, particularly in the C-band (1530-1565 nm). This is because mature optical communication technologies can be leveraged for transmission, manipulation, and detection. Additionally, to achieve high-speed quantum information processing, Fock states should be generated in optical pulses with as short a duration as possible, as this allows embedding lots of information in the time domain. In this paper, we successfully generate picosecond pulsed multi-photon Fock states (single-photon and two-photon states) in the C-band with Wigner negativities for the first time, which are verified by pulsed homodyne tomography. In our experimental setup, we utilize a single-pixel superconducting nanostrip photon-number-resolving detector (SNSPD), which is expected to facilitate the high-rate generation of various quantum states. This capability stems from the high temporal resolution of SNSPDs (several tens of picoseconds in our case and also in general) allowing us to increase the repetition frequency of pulsed light from the conventional MHz range to the GHz range, although in this experiment the repetition frequency is limited to 10 MHz due to the bandwidth of the homodyne detector. Consequently, our experimental setup is anticipated to serve as a prototype of a high-speed optical quantum state generator for ultrafast quantum information processing at telecommunication wavelength.

Harnessing a WOx-based flexible transparent memristor synapse with a hafnium oxide layer for neuromorphic computing.

Transparent memristor-based neuromorphic synapses are expected to be specialised devices for high-speed information transmission and processing. The synaptic linearity and potentiation/depression cycles are imperative issues for the application of memristors. This work explores a memristor for improving switching uniformity by introducing a thin HfOx interfacial layer as a diffusion-limiting layer sandwiched between WOx and ITO bottom electrodes. An optimized HfOx thickness not only provides the best switching properties but also shows superior synaptic properties. The optimized 15 nm thin WOx layer can retain the memristor's excellence in P/D linearity, a cycling stability of 494 epochs and image recognition up to 3 mm bending, making it suitable for flexible devices. The artificial synapse is capable of reversible short-term and long-term learning behaviors confirmed by spike-timing-dependent-plasticity (STDP) results. X-ray photoelectron spectroscopy confirms the device composition and provides the oxygen vacancy concentration at the WOx/HfOx interface to realize the switching mechanism. The thicknesses of the different layers are estimated from the high-resolution transmission electron microscopy observations. The fabricated device exhibits 92.2% transparency, as confirmed by the UV-Vis spectrum.

Optically-reconfigurable integrated optical directed logic computing based on silicon photonics.

Optical directed logic, as a novel logical operation scheme, harmoniously combines the benefits of optical and electrical signals, surpassing traditional electrical and all-optical logic operations in terms of the flexibility and power consumption. Its potential in high-speed optical signal processing and electro-optical computing is immense. However, achieving tunability of the logic function normally relies on external electrical tuning or multiple laser sources, which often results in excessive power consumption and costs. In this work, by utilizing the polarization state of light within the optical directed logic, we demonstrate an optical directed logic device on a silicon-based platform. This single device can realize three different logic operations, which are XNOR, XOR and NAND, by simply changing the input light's polarization state, which comes at a minimal additional power consumption. Moreover, we also significantly enhance the device's response speed through a novel side-integrated metal thermal phase shifter, reducing the response time to 5 µs. Ultimately, we demonstrate logic operations at 60 kbps which maintains a leading standard among the currently reported thermally tuning optical-directed logic (ODL) devices, and successfully integrated polarization division multiplexing technique into ODL devices. This result provides a novel method to realize high-speed optical directed logic with high reconfigurability, which presents significant application prospects in the high-speed optical information processing field.

UV-enhanced photorefractive response rate in a thin-film lithium niobate microdisk.

The photorefractive (PR) effect plays a critical role in emerging photonic technologies, including dynamic volume holography and on-chip all-optical functionalities. Nevertheless, its slow response rate has posed a significant obstacle to its practical application. Here, we experimentally demonstrate the enhancement of the PR response rate in a high-Q thin-film lithium niobate (TFLN) microdisk under UV light irradiation. At an irradiation intensity of 30 mW/cm2, the PR effect achieves a high response bandwidth of approximately 256 kHz. By employing this UV-assisted PR effect, we have achieved rapid laser-cavity locking and self-stabilization, where perturbations are automatically compensated. This technique paves the way toward real-time dynamic holography, editable photonic devices on a lithium niobate platform, and high-speed all-optical information processing.

All-optical free-space routing of upconverted light by metasurfaces via nonlinear interferometry.

All-optical modulation yields the promise of high-speed information processing. In this field, metasurfaces are rapidly gaining traction as ultrathin multifunctional platforms for light management. Among the featured functionalities, they enable light-wavefront manipulation and more recently demonstrated the ability to perform light-by-light manipulation through nonlinear optical processes. Here, by employing a nonlinear periodic metasurface, we demonstrate the all-optical routing of telecom photons upconverted to the visible range. This is achieved via the interference between two frequency-degenerate upconversion processes, namely, third-harmonic and sum-frequency generation, stemming from the interaction of a pump pulse with its frequency-doubled replica. By tuning the relative phase and polarization between these two pump beams, we route the upconverted signal among the diffraction orders of the metasurface with a modulation efficiency of up to 90%. This can be achieved by concurrently engineering the nonlinear emission of the individual elements (meta-atoms) of the metasurface along with its pitch. Owing to the phase control and ultrafast dynamics of the underlying nonlinear processes, free-space all-optical routing could be potentially performed at rates close to the employed optical frequencies divided by the quality factor of the optical resonances at play. Our approach adds a further twist to optical interferometry, which is a key enabling technique employed in a wide range of applications, such as homodyne detection, radar interferometry, light detection and ranging technology, gravitational-wave detection and molecular photometry. In particular, the nonlinear character of light upconversion combined with phase sensitivity is extremely appealing for enhanced imaging and biosensing.

Terahertz spin currents resolved with nanometer spatial resolution

The development of coherent terahertz (THz) spin currents with femtosecond temporal resolution has been extensively studied due to its significant implications for advancing high-speed information processing devices. However, the precise spatial resolution of THz spin currents, which is crucial for increasing storage density, is still unknown. In this study, we employ spintronic THz emission nanoscopy (STEN) to achieve efficient injection and accurate detection of femtosecond THz spin currents with nanoscale lateral spatial resolution (∼60 nm). The occurrence of emission signals at the fifth harmonic order indicates a substantial signal-to-noise ratio. Additionally, STEN proves to be an effective method for characterizing and etching nanoscale spintronic heterostructures. The integration of nanophotonics, nanospintronics, and THz-nanotechnology into a unified platform is poised to enable the characterization of spin states at micro-to-nanoscale densities, accelerate the development of high-frequency spintronic optoelectronic nanodevices, and catalyze other revolutionary technical applications.

Label-Free Cell Detection of Acute Leukemia Using High-Content Morphological Profiling in Flow

Background: Early diagnosis and prompt initiation of appropriate treatment are critical for improving the prognosis of acute leukemia. Acute leukemia is typically diagnosed through microscopic morphological examination of bone marrow smears and flow cytometric immunophenotyping of bone marrow cells stained with fluorophore-conjugated antibodies. However, these diagnostic processes require trained professionals and are time and resource-intensive. Here, we present a novel diagnostic approach using ghost cytometry (GC), a recently developed high-content flow cytometric approach that leverages machine vision-based, stain-free, high-speed morphological characterization and analysis of cells. Methods: Label-free morphological information of cells was acquired as compressive imaging temporal waveforms. These waveforms were directly analyzed using the support vector machine (SVM) algorithm without computational image production, enabling high-speed and accurate information processing. Conventional flow cytometric data modalities, such as forward-scattering (FSC), backscattering (BSC), and fluorescence signals from biological labeling, were used as ground truth labels to identify and annotate blast and normal cells in bone marrow (BM) based on flow cytometric gating schemes. Subsequently, we trained a leukemia cell classifier using the annotated GC (compressive imaging) waveforms and evaluated its classification ability by comparing the predicted results with the ground truth labels. Finally, we applied the trained classifier to unidentified GC waveforms (a test dataset not used for classifier development) to demonstrate the detection of blast cells in BM based on their morphology, without relying on biological labels. Following this protocol, we first trained and tested a machine classifier using a human leukemia NB-4 cell line spiked into BM from a healthy donor. Next, we trained and tested two classifiers using BM aspirates from patients diagnosed with acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML), where CD45 was used as the ground truth marker of leukemic cells. Results: The leukemia cell classifier, developed using a human NB-4 cell line spiked into BM cells from a healthy donor, demonstrated excellent classification accuracy with an ROC-AUC score of 0.9998. The high classification accuracy was reproducible across different spike-in concentrations ranging from 1% to 95%. The classifiers trained using BM cells from patients diagnosed with ALL and AML showed high ROC-AUC scores of 0.986 and 0.941, respectively. When we used the classifiers to evaluate blast cell proportions in test datasets that were not used to develop the classifiers, they were also highly accurate in identifying the percentage of blast cells: 56.8% for ALL with a decision boundary of SVM scores at 0, and 30.4% for AML with a decision boundary of SVM scores at 0.37, when compared to May-Grunwald-Giemsa staining of the same cases by medical technologists at diagnosis (60.0% for ALL and 31.2% for AML). Conclusions: Here, we present a novel diagnostic approach that leverages machine vision-based, stain-free, high-speed morphological characterization and analysis of cells. We demonstrate that the approach can detect leukemic cells from the bone marrow cells of patients diagnosed with ALL and AML, without requiring biological staining. The method presented here holds promise as a rapid, precise, simple, and cost-effective method for the diagnosis of acute leukemia in clinical settings.

Quantifying the Accuracy of Microcomb-Based Photonic RF Transversal Signal Processors

Photonic RF transversal signal processors, which are equivalent to reconfigurable electrical digital signal processors but implemented with photonic technologies, have been widely used for modern high-speed information processing. With the capability of generating large numbers of wavelength channels with compact micro-resonators, optical microcombs bring new opportunities for realizing photonic RF transversal signal processors that have greatly reduced size, power consumption, and complexity. Recently, a variety of signal processing functions have been demonstrated using microcomb-based photonic RF transversal signal processors. Here, we provide detailed analysis for quantifying the processing accuracy of microcomb-based photonic RF transversal signal processors. First, we investigate the theoretical limitations of the processing accuracy determined by tap number, signal bandwidth, and pulse waveform. Next, we discuss the practical error sources from different components of the signal processors. Finally, we analyze the contributions of the theoretical limitations and the experimental factors to the overall processing inaccuracy both theoretically and experimentally. These results provide a useful guide for designing microcomb-based photonic RF transversal signal processors to optimize their accuracy.

Compact generation scheme of path–frequency hyperentangled photons using 2D periodical nonlinear photonic crystal

Hyperentanglement is a promising resource for achieving high capacity quantum communication. Here, we propose a compact scheme for the generation of path–frequency hyperentangled photon pairs via spontaneous parametric down-conversion (SPDC) processes, where six different paths and two different frequencies are covered. A two-dimensional periodical χ (2) nonlinear photonic crystal (NPC) is designed to satisfy type-I quasi-phase-matching conditions in the plane perpendicular to the incident pump beam, and a perfect phase match is achieved along the pump beam’s direction to ensure high conversion efficiency, with theoretically estimated photon flux up to 2.068 × 105 pairs⋅s−1⋅mm−2. We theoretically calculate the joint-spectral amplitude (JSA) of the generated photon pair and perform Schmidt decomposition on it, where the resulting entropy S of entanglement and effective Schmidt rank K reach 3.2789 and 6.4675, respectively. Our hyperentangled photon source scheme could provide new avenues for high-dimensional quantum communication and high-speed quantum information processing.

Modulo-addition operation enables terahertz programmable metasurface for high-resolution two-dimensional beam steering.

Electrically controlled terahertz (THz) beamforming antennas are essential for various applications such as wireless communications, security checks, and radar to improve coverage and information capacity. The emerging programmable metasurface provides a flexible, cost-effective platform for THz beam steering. However, scaling such arrays to achieve high-gain beam steering faces several technical challenges. Here, we propose a pixelated liquid crystal THz metasurface with a crossbar structure, thereby increasing the array scale to more than 3000. The coding pattern on the programmable device is generated by the modulo-addition of the coding sequences on the top and bottom layers. We experimentally demonstrate the programmable liquid crystal metasurface capable of active beam deflection in the upper half-space. This scale-up of programmable devices opens exciting opportunities in pencil beamforming, high-speed information processing, and optical computing.

Comparison of Microcomb-Based Radio-Frequency Photonic Transversal Signal Processors Implemented with Discrete Components Versus Integrated Chips.

RF photonic transversal signal processors, which combine reconfigurable electrical digital signal processing and high-bandwidth photonic processing, provide a powerful solution for achieving adaptive high-speed information processing. Recent progress in optical microcomb technology provides compelling multi-wavelength sources with a compact footprint, yielding a variety of microcomb-based RF photonic transversal signal processors with either discrete or integrated components. Although they operate based on the same principle, the processors in these two forms exhibit distinct performances. This paper presents a comparative investigation of their performances. First, we compare the performances of state-of-the-art processors, focusing on the processing accuracy. Next, we analyze various factors that contribute to the performance differences, including the tap number and imperfect response of experimental components. Finally, we discuss the potential for future improvement. These results provide a comprehensive comparison of microcomb-based RF photonic transversal signal processors implemented using discrete and integrated components and provide insights for their future development.

Prospects of the nanoelectronic element base of infosystems of autonomous aircraft

The ways of creating a nanoelectronic element base (NEB) of Autonomous Air Vehicle (AАV) with small dimen-sions and weight are analyzed. The autonomy of these devices predetermines the principles of building their in-formation systems using artificial intelligence logic, significant memory resources, as well as functionally special-ized and high-speed information processing methods. And the cost restrictions involve the use of practically de-bugged nano- and microtechnologies for optical devices and integrated circuits. In addition, the small volume and weight of AAV necessitate the miniaturization of their NEB. At the same time, the operation of the AAV in various extreme conditions with increased radiation and bursts of the electromagnetic field (for example, in space) is not ruled out. Under these conditions, the semiconductor elements of their electronics are likely to fail. Therefore, in NEB of AAV, it is expedient to switch to nanovacuum-channel transistors (NVCT), which do not have semiconduc-tors (or their role is auxiliary). In NVKT, the nanochannel of electron transfer between the electrodes is replaced by a vacuum one, and the control is carried out by the voltage on the field electrode - the gate. At the same time, the nanoscale length of the gap between the emitter and the collector provides low voltages on the electrodes of the NVKT. In general, replacing a semiconductor with a vacuum can simplify and reduce the cost of transistor technol-ogy, make it more resistant to radiation and high-energy fields, and will allow to reach THz frequencies. And the creation of new types of NVKT (for example, using the control of the electron spin orientation) will increase the per-formance of AAV information transmission and processing tools.

Characteristic Analysis and Application of the Optoelectronic Neural Network

In recent years, optoelectronic neural networks have garnered significant attention due to their potential to facilitate high-speed and efficient information processing by employing light-based signals to transmit and process data. This review provides an overview of the current state-of-the-art in optoelectronic neural networks, including their design principles, fabrication techniques, and applications. The article also presents five different methods for constructing optoelectronic neural networks, which offer insights into current ONN research and solutions to overcome the limitations of traditional neural networks. Furthermore, the review discusses three different applications of ONNs, including basic tasks such as data classification, speech recognition, and image recognition, as well as hardware accelerators and SNN algorithms for object detection. The promising potential of optoelectronic neural networks in transforming various fields, such as artificial intelligence, image recognition, and data processing, is also highlighted. As research in this area continues to advance, further breakthroughs in optoelectronic neural networks are anticipated.

Characteristics of ultrafast response induced by impulsive interference of excitons in a GaAs/AlAs multiple quantum well on a slightly strained buffer layer

Ultrafast responses caused by ultrashort pulse excitation can be applied to ultrafast optical switches with high-speed information processing. In this paper, via the impulsive interference of excitons, we achieve an ultrafast optical response suited for ultrafast switches in all-optical networks. Due to the simultaneous excitation of two exciton states in the multiple quantum well on a strained buffer layer without the occurrence of adverse effects like stacking faults, impulsive interference is induced. The small compressive strain from the buffer layer modifies the orientation of the excitons inside the quantum well, and causes the ultrafast response.

Capturing ultra-broadband complex-fields of arbitrary duration using a real-time spectrogram

One of the most intuitive representations of a waveform is achieved through time-frequency analysis, which depicts how the frequency components of a wave evolve over time. Time-frequency representations, such as the spectrogram, are well-known for allowing full-field characterization of a signal in terms of amplitude and phase. However, present methods to capture the spectrogram of a waveform are only suited for either relatively slow (<GHz bandwidth) waveforms of arbitrary duration or fast (>THz bandwidth) waveforms of short duration. It remains very challenging to capture the time-frequency representation of broadband waves extending over long durations, as required for many important fields in science and technology. Here, we introduce a linear optics temporal imaging concept based on electro-optic time-lensing and dispersive propagation to map the 2D spectrogram as a 1D waveform along the temporal domain. This technique enables ultra-broadband spectrogram analysis without any gaps in the acquisition and with no inherent limitation on maximum signal duration. The spectrogram is captured at unmatched processing rates, up to 16 × 109 Fourier transforms per second (∼60 ps per spectral frame), using a single photodetector and in a fully self-referenced manner. Under certain conditions, we show how this method enables the single-shot full-field characterization of optical waveforms spanning multiple THz. The method is further showcased through accurate amplitude and phase recovery of high-speed complex-modulated optical telecommunication signals using direct intensity detection. This concept will enable the study of physical phenomena unreachable to date and disruptive advancements in high-speed communications, sensing, and information processing.

Ultrafast Graphene-Plasmonic Hybrid Metasurface Saturable Absorber with Low Saturation Fluence.

Exploring emerging materials with enhanced optical nonlinearities at low power levels with ultrafast response and small footprints is of great interest for information processing, communication, sensing, and quantum systems. Recent progress on nonlinear metamaterials and metasurfaces suggests promising solutions to overcome the limitations of nonlinear materials in nature. Here we present a design concept for highly enhanced saturable absorption effect based on subwavelength-thick (<1/5λ0) hybrid graphene-plasmonic metasurface structures in infrared wavelengths. Our theoretical and experimental results demonstrated that, by exciting nonequilibrium carriers inside nanoscale hotspots, one could not only enhance the saturable absorption in graphene, but also reduce the saturation fluence by over 3 orders of magnitude (from ∼1 mJ/cm2 to ∼100 nJ/cm2). Our pump-probe measurement results suggested an ultrashort saturable absorption recovery time (<60 fs), which is ultimately determined by the relaxation dynamics of photoexcited carriers in graphene. We also observed pulse narrowing effects in our devices based on the autocorrelation measurement results. Such design concepts can be tailored via structure engineering to operate in broader wavelength ranges up to mid- and far- infrared spectral regions. These ultrafast low-saturation fluence saturable absorber designs can enable low-threshold, compact, self-starting mode-locked lasers, laser pulse shaping, and high-speed optical information processing.