Optical computing chips have emerged as a transformative computing technology due to their high computational density, low energy consumption, and compact footprint. While real- and complex-valued computing chips have been well developed, their fundamental limitations in representing high-dimensional data significantly constrain their applicability in modern signal processing. Quaternions enable direct operations on three- and four-dimensional data, powering high-dimensional processing in data analytics and artificial intelligence. Here we demonstrate a quaternion optical computing chip (QOCC) for the first time and benchmark its performance in several typical application scenarios: three-dimensional point cloud processing, RGB chromatic transformation, and quaternion convolutional neural network for color image recognition. The QOCC harnesses high parallelism of light by wavelength-division multiplexing, processing high-dimensional data simultaneously through multiple optical wavelength channels. Compared to the electronic computing counterpart, our QOCC achieves higher computational fidelity (root mean square error < 0.035) and substantially reduced computational load (2/3 lower). It paves the way towards next-generation optical computing, overcoming the limitations of traditional computing systems in high-dimensional data processing.

Magnetoelectric heterostructures integrating piezoelectric and magnetostrictive phases have emerged as a compelling material platform for investigating high-frequency magnetization dynamics and magnetoelastic coupling via acoustic wave excitation. This work presents magnetically tunable 1.015 GHz acoustic delay lines (ADLs) based on AlN/FeGaB heterostructure films, demonstrating both in-band phase and amplitude modulation capabilities. By investigating three characteristic frequency peaks (997.2 MHz, 1015.7 MHz, and 1027.5 MHz) within the device passband, it is observed that tunability tends to be enhanced near the modal peak frequencies where insertion loss is low. Under a magnetic field of 160 Oe with the acoustic wave direction perpendicular to the magnetic field (θ = 90°), the device achieves a maximum differential phase shift of 4.07° and an amplitude modulation of approximately 0.25 dB at 1015.7 MHz. Furthermore, linear phase and amplitude modulations of 3.23°/120 Oe and 0.19 dB/170 Oe are obtained at θ = 90°. These results experimentally demonstrate the feasibility of magnetic-field-engineered control in Lamb-wave acoustic delay lines, highlighting their strong potential for reconfigurable RF front-end applications.

Modes provide a fundamental degree of freedom for photonic information processing, yet conventional multimode waveguides exhibit non-equidistant effective-index distributions, making closely spaced modes vulnerable to intermodal crosstalk. Supermode photonics can overcome this limitation by geometrically engineering coupled waveguide arrays to realize large and equidistant effective-index spacing, but precise supermode excitation and detection remain challenging at the subwavelength scale. Here, we report a hierarchical second-order discrete supersymmetric (DSUSY) transformation method that enables high-purity excitation and extraction of arbitrary target supermodes in a compact and scalable architecture. We experimentally demonstrate six-supermode multiplexing systems on silicon-on-insulator and silicon nitride platforms. Benefiting from the large supermode index spacing and the isospectrality of DSUSY transformations, the fabricated devices exhibit low insertion losses (<2.6 dB) and intermodal crosstalk (<-11.1 dB) for all channels over a 100-nm wavelength range. A high-speed transmission experiment on the silicon device achieves an aggregate data rate of 1.2 Tbit/s, with all channel bit error rates below the 7

We report a systematic methodology to obtain supermodes with equidistant effective index distribution and to excite arbitrary target supermodes with high precision. By employing a multi-well optical potential realized by a judiciously designed waveguide array, the supported supermodes achieve maximal spacing and an equidistant distribution in effective index. More importantly, we develop a 2nd-order discrete supersymmetric (DSUSY) transformation method that enables the excitation and detection of two supermodes at the same time and can be extended to any number of supermodes via simple cascading. Together, these findings overcome the long-standing bottlenecks in integrated supermode photonics and provide an intrinsically scalable route towards harnessing supermodes as a new degree of freedom for encoding, transmitting, and processing information. We experimentally demonstrate the feasibility and universality of this method by realizing two- and four-supermode multiplexing systems. Benefitting from the large effective index spacing between supermodes and the isospectral nature of the DSUSY transformation, the fabricated devices show low insertion losses (< 2.48 dB at 1550 nm) and intermodal crosstalk (< -18 dB at 1550 nm) for all mode channels over a 100-nm wavelength range (1500-1600 nm). The high-speed data transmission experiment performed on the four-channel system achieves an aggregate data rate of 1.024 Tb/s while maintaining considerably low bit error rates, underscoring the potential of supermode photonics for high-capacity on-chip optical communications. This work lays the foundation for integrated supermode photonics, which uses supermodes as a new degree of freedom for light manipulation and opens new avenues for supermode-based applications including but not limited to on-chip optical communications, intelligent optical computing and quantum information technologies.

High-performance multimode optical devices are critical for photonic integrated circuits (PICs) and mode-division multiplexing (MDM), but conventional fiber-based multimode circulators (MMC) lack compactness and most on-chip circulators only support single-mode operation, limiting on-chip multimode transmission. To address this, we propose and demonstrate a simplified, N-mode-scalable on-chip MMC. Incorporating two symmetric N-junctions and ⌊N/2⌋ tapered π-phase shifters, it supports off-chip multi-port and on-chip multi-mode circulation. The fabricated silicon waveguide 3-mode prototype with chip size ~4.5 × 223.5 μm2 shows insertion loss <1.9 dB at wavelength 1550 nm (<3.8 dB over 1500-1620 nm), and crosstalk <-12.1 dB. It provides a novel solution for on-chip MDM directional transmission and isolation, promoting the advancement of multi-mode PICs.

ABSTRACT On‐chip stimulated Brillouin scattering (SBS) technology has garnered attention in the field of integrated photonics due to its unique acousto–optic coupling characteristics and potential for all‐optical signal processing systems. By leveraging efficient Brillouin acousto–optic interactions, a variety of high‐performance on‐chip SBS‐based devices have been successfully demonstrated, including narrow‐linewidth lasers, low‐noise amplifiers, high‐precision gyroscopes, tunable filters, and optical isolators. In this review, we first summarize the physical mechanisms of SBS and the key methods for calculating gain characteristics on integrated optical platforms. We then discuss the implementation schemes of the Brillouin effect in different material platforms, along with their emerging applications in optical communications, quantum information, and other fields. Finally, we outline the current technological challenges and prospective research, which may provide insights into the design of next‐generation integrated acousto–optic devices.

Coupled resonator optical waveguides (CROWs) are widely used for filtering, storing, and enhancing light-matter interactions. However, their bandwidth, which characterizes the operation wavelength range, is fundamentally limited by the tradeoff between the free spectral range (FSR) and finesse. To address this limitation, we introduce topological coupler into CROWs, significantly enlarging their bandwidth. By leveraging the topology and symmetry of topological coupler, the finesse of CROW is independent of its FSR, which efficiently relieves the tradeoff. Our topological CROW achieves a bandwidth of 9.0 nm. By cascading such CROWs, we realize a topological two-channel add-drop filter with a bandwidth of over 4.7 nm, even with dimensional errors up to 20 nm. Furthermore, high-speed data transmission at 170 Gb/s is realized in the topological filter. Our broadband topological CROWs and filter offer new opportunities for robust optical buffering, broadband modulation, and novel polariton applications.

In passive optical networks (PONs), due to the limited optical power budget, dynamic and non-uniform power distribution among different links is often required to compensate for transmission losses. Therefore, reconfigurable beam splitters featuring low loss, non-volatility, and fast tuning capability have become key building blocks for flexible optical distribution units (ODUs) as well as for programmable optical networks and photonic computing. Here, we experimentally demonstrate an electrically reconfigurable beam splitter based on the low-loss phase-change material Sb2Se3, enabling multi-level and arbitrary splitting-ratio control. By locally triggering phase transitions in the coupling region with integrated micro-electrodes, we exploit the high refractive index contrast between different phases and negligible absorption in the near infrared wavelength of Sb2Se3 to precisely tune the coupling strength with non-volatile retention. 18-level of power splitting states is achieved within a compact footprint of similar to 14.5 & micro;m in the experiments, with an insertion loss of similar to 1 dB across 1500-1560 nm and near-zero static power. Combining the advantages of compactness, broad bandwidth, low-loss, non-volatility, and multi-level control experimentally, this device provides a universal building block for scalable, energy-efficient reconfigurable photonic circuits, with great prospects in optical computing and intelligent communication systems.

Topological photonic crystals (TPCs) have attracted extensive attention for their ability to support robust, backscattering-immune light propagation, offering a promising path toward high-performance, large-scale photonic integration systems. Although significant progress has been made in elucidating the fundamental topological properties and developing innovative TPC-based devices, their potential to overcome practical challenges remains largely unexplored. Here, we take a substantial step forward by leveraging the topological protection inherent to TPCs to mitigate stitching losses caused by lithography field misalignment. We design and experimentally demonstrate a topological valley photonic crystal (VPC) waveguide on the silicon-on-insulator (SOI) platform. Compared with a conventional 0.5 & micro;m-wide waveguide, the proposed VPC waveguide reduces stitching losses from 0.59 to 0.009 dB and from 1.53 to 0.54 dB under 100 nm lateral and longitudinal field misalignments at a wavelength of 1550 nm, corresponding to reductions of 98.3% and 64.7%, respectively. The robustness of VPC waveguides persists even under severe misalignments of up to 500 nm, equivalent to the width of a conventional waveguide. These findings not only highlight the practical viability of TPCs under realistic fabrication constraints but also pave the way for large-scale, fabrication-resilient photonic integration.

Self-generated spin-orbit torque (SOT) in magnetic materials has emerged as a promising pathway for efficient magnetization control without external spin current sources. Here, we unveil an alternative mechanism for deterministic SOT polarity control based on inversion symmetry engineering via ferromagnet (Co) thickness gradients in [Co/Pt](p) multilayers with the repeating periods p. Unlike conventional approaches relying on spin Hall effect asymmetry in heavy metals, we modulate the spatial profile of spin current absorption and reflection across the stack, creating a net damping-like SOT driven by gradient-induced imbalanced spin accumulation. By inverting the Co gradient, we achieved polarity-reversed perpendicular magnetization switching, demonstrating that the SOT originates from structural symmetry breaking within the ferromagnetic layers. Second harmonic measurements confirm robust SOT switching efficiencies up to 294 Oe cm(2) MA(-1), along with enhanced thermal stability and scalability beyond bilayer systems. Our findings establish the symmetry-governed design principle for spin transport, enabling tunable and thickness-robust spintronic devices.

ABSTRACT In passive optical networks (PONs), due to the limited optical power budget, dynamic and non‐uniform power distribution among different links is often required to compensate for transmission losses. Therefore, reconfigurable beam splitters featuring low loss, non‐volatility, and fast tuning capability have become key building blocks for flexible optical distribution units (ODUs) as well as for programmable optical networks and photonic computing. Here, we experimentally demonstrate an electrically reconfigurable beam splitter based on the low‐loss phase‐change material Sb 2 Se 3 , enabling multi‐level and arbitrary splitting‐ratio control. By locally triggering phase transitions in the coupling region with integrated micro‐electrodes, we exploit the high refractive index contrast between different phases and negligible absorption in the near infrared wavelength of Sb 2 Se 3 to precisely tune the coupling strength with non‐volatile retention. 18‐level of power splitting states is achieved within a compact footprint of ∼14.5 µm in the experiments, with an insertion loss of ∼1 dB across 1500–1560 nm and near‐zero static power. Combining the advantages of compactness, broad bandwidth, low‐loss, non‐volatility, and multi‐level control experimentally, this device provides a universal building block for scalable, energy‐efficient reconfigurable photonic circuits, with great prospects in optical computing and intelligent communication systems.

We propose a robust algorithm for detecting R-peaks in terahertz-wave plethysmography (TPG) signals to enable accurate pulse rate estimation. Unlike prior methods based on frequency domain analysis, our approach integrates adaptive thresholding and dynamic filtering to identify individual R-peaks in time-domain THz signals. Evaluations using reference photoplethysmography (PPG) data show significant reductions in both mean absolute error (MAE) and root mean square error (RMSE), highlighting the algorithm's potential in non-contact heart rate variability (HRV) monitoring.

The generation and control of multidimensional optical fields play a crucial role in advancing applications such as optical communications, sensing, information encoding, and imaging, by maximizing the utilization of optical degrees of freedom and enabling multiple optical channels. Optical lasers are fundamental to these applications as the primary sources of optical fields. However, previous work mainly focused on realizing light sources based on fundamental modes, leaving higher-order modes underutilized. Here, we propose an approach for generating and controlling an on-chip higher-order-mode light source from Raman lasing. We chose the fourth-order mode as an example and generated the fourth-order mode lasing using a compact, high-quality multimode silicon racetrack resonator. The multimode racetrack resonator has a compact footprint of 0.13 mm2 using two adiabatic bends and exhibits a high-quality factor of over 1 x 106. The lasing threshold was measured as 0.6 mW. Finally, we show that controlling the higher-order-mode lasing enables mode-switching behavior, which can find potential applications in high-resolution optical systems and quantum optics.

Reconfigurable beam splitters capable of being arbitrarily programmed for the power splitting ratios are vital for the adaptive optical networks and photonic computing. Conventional mechanisms such as thermo-optic, free-carrier, or mechanical tuning are usually volatile and require continuous power, limiting their suitability for low-frequency and low power-consumption programmable operations. Here, we experimentally demonstrate an electrically reconfigurable beam splitter based on the low-loss phase-change material Sb2Se3, enabling multi-level and arbitrary splitting-ratio (SR) control. By locally triggering phase transitions in the coupling region with integrated micro-electrodes, we exploit the high refractive-index contrast between different phases and negligible absorption in the near-infrared wavelength of Sb2Se3 to precisely tune the coupling strength with non-volatile retention. 8-level of power splitting states is achieved within a compact footprint of 14.5-μm in the experiments, with insertion loss is 1 dB across 1515-1550 nm and near-zero static power. Combining the advantages of compactness, broad bandwidth, low loss, non-volatility, and multi-level control experimentally, this device provides a universal building block for scalable, energy-efficient reconfigurable photonic circuits, with great prospects in optical computing and intelligent communication systems.

Topological edge states in valley photonic crystals (VPCs) have gained significant attention due to their capabilities for sharp‐turn transmission, defect immunity, and robust photon transport on chips. However, research on the refraction within the VPC domain in photonic integrated chips is still lacking, impeding various applications of VPCs. In this work, the refraction mechanisms of topological edge modes at different external coupling boundaries are investigated, and demonstrate topological interconnections and switches on a chip. The reflection of topological modes refracted into slab waveguides is compared through zigzag, armchair, and vertical zigzag terminations. The vertical zigzag termination demonstrates high external coupling efficiency with a constant refraction angle at different wavelengths. Based on these findings, a compact and low‐loss waveguide crossing for configurable topological interconnections. To demonstrate practical applications a compact 2 × 2 topological switch is presented that utilizes the proposed crossing and a topological Mach‐Zehnder interferometer (MZI) structure is proposed. This work explores the refraction mechanisms of topological edge modes at different external coupling boundaries, expanding the potential applications of topological edge states in integrated photonic circuits, optical communications, and quantum information processing.

We propose and experimentally demonstrate directional couplers with arbitrary coupling ratios using pseudomagnetic fields (PMFs) in silicon photonic crystals at telecommunication wavelengths. This work may enable diverse PMF-based functional devices in many fields, such as quantum information processing, nanophotonics, and optical communications.

Coupled-waveguide devices are essential in photonic integrated circuits for coupling, polarization handling, and mode manipulation. However, the performance of these devices usually suffers from high wavelength and structure sensitivity, which makes it challenging to realize broadband and reliable on-chip optical functions. Recently, topological pumping of edge states has emerged as a promising solution for implementing robust optical couplings. In this paper, we propose and experimentally demonstrate broadband on-chip mode manipulation with very large fabrication tolerance based on the Rice-Mele modeled silicon waveguide arrays. The Thouless pumping mechanism is employed in the design to implement broadband and robust mode conversion and multiplexing. The experimental results prove that various mode-order conversions with low insertion losses and intermodal crosstalk can be achieved over a broad bandwidth of 80 nm ranging from 1500 to 1580 nm. Thanks to such a topological design, the device has a remarkable fabrication tolerance of +/- 70 nm for the structural deviations in waveguide width and gap distance, which is, to the best of our knowledge, the highest among the coupled-waveguide mode-handling devices reported so far. As a proof-of-concept experiment, we cascade the topological mode-order converters to form a four-channel mode-division multiplexer and demonstrate the transmission of a 200-Gb/s 16-quadrature amplitude modulation signal for each mode channel, with the bit error rates below the 7% forward error correction threshold of 3.8x10(-3). We reveal the possibility of developing new classes of broadband and fabrication-tolerant coupled-waveguide devices with topological photonic approaches, which may find applications in many fields, including optical interconnects, quantum communications, and optical computing.

Pseudomagnetic fields (PMFs) can manipulate photons in a similar way that magnetic fields control electrons. However, the PMF-based control over light has been restricted to simple waveguiding of the Landau level states, which hinders the application of PMFs in practical photonic integrated circuits. Here, we propose a universal and systematic methodology to design complex nonuniform PMFs and arbitrarily control the flow of light in silicon photonic crystals at telecommunication wavelengths. As proofs of concept, an S-bend (with a low insertion loss of <1.83 dB) and a 50:50 power splitter (with a low excess loss of <2.11 dB and imbalance of less than +/- 0.5 dB) based on PMFs are experimentally demonstrated. A high-speed data transmission experiment is performed on these devices with 140-Gb/s four-level pulse amplitude modulation signals to prove their applicability in real communication systems. The proposed method offers a paradigm for exploring magnetic-field-related physics with neutral particles and developing nanophotonic devices with PMF-induced states beyond the Landau level states and the topological edge states.