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Electro-optic modulators have been identified as the key drivers for optical communication and signal processing. With an ongoing miniaturization of photonic circuitries, an outstanding aim is to demonstrate an on-chip, ultra-compact, electro-optic modulator without sacrificing bandwidth and modulation strength. While silicon-based electro-optic modulators have been demonstrated, they require large device footprints of the order of millimeters as a result of weak non-linear electro-optical properties. The modulation strength can be increased by deploying a high-Q resonator, however with the trade-off of significantly sacrificing bandwidth. Furthermore, design challenges and temperature tuning limit the deployment of such resonance-based modulators. Recently, novel materials like graphene have been investigated for electro-optic modulation applications with a 0.1 dB per micrometer modulation strength, while showing an improvement over pure silicon devices, this design still requires device lengths of tens of micrometers due to the inefficient overlap between the thin graphene layer, and the optical mode of the silicon waveguide. Here we experimentally demonstrate an ultra-compact, silicon-based, electro-optic modulator with a record-high 1 dB per micrometer extinction ratio over a wide bandwidth range of 1 μm in ambient conditions. The device is based on a plasmonic metal-oxide-semiconductor (MOS) waveguide, which efficiently concentrates the optical modes’ electric field into a nanometer thin region comprised of an absorption coefficient-tuneable indium-tin-oxide (ITO) layer. The modulation mechanism originates from electrically changing the free carrier concentration of the ITO layer which dramatically increases the loss of this MOS mode. The seamless integration of such a strong optical beam modulation into an existing silicon-on-insulator platform bears significant potential towards broadband, compact and efficient communication links and circuits.

Topological photonics offer transformative potential for robust integrated waveguide devices due to their backscattering‐immune properties. However, their integration faces two fundamental challenges: mode symmetry mismatch with conventional waveguides and prohibitive dimensions. We successfully overcome these two critical challenges by introducing a novel valley‐ridge gap waveguide based on topological half‐supermode engineering. By strategically hybridizing ridge waveguide modes and valley kink states, we create an exotic odd‐symmetric supermode enabling robust propagation and ultra‐compact operation. The further implementation of a perfect electric conductor boundary halves the lateral dimensions while eliminating radiation loss. Crucially, our proposed valley–ridge interface achieves direct transverse electric mode matching with standard waveguides without transition structures, enabling seamless integration. Experimental results demonstrate reflection losses lower than −15 dB in realistic telecommunication scenarios with super‐robust signal propagation through sharp bends. This work innovatively conceptualizes topological half‐supermodes and pioneers their practical applications for integrated waveguide devices, establishing a completely new waveguide class that uniquely combines robust backscattering immunity with deep subwavelength compactness. Through topological half‐supermode engineering, we realize a valley‐ridge gap waveguide that is directly compatible with conventional waveguides and features topological protection. This design halves the lateral size via a PEC boundary, enabling direct TE₁₀‐mode matching and robust bend‐immune transmission. We thus establish a new class of compact, directly integrable mmWave waveguides. .

This research reports a conformal ultra-compact millimeter-Wave microwave access narrowband four-port MIMO 60.0 GHz antenna designed for 60.0 GHz future high-speed wireless applications. The proposed 60.0 GHz MIMO 60.0 GHz antenna radiating electromagnetic energy occupies a minimal space of 16 × 16 mm 2 with a rectangular patch connected to defected microstrip structure on one-plane of RogersRTDuroid TM 5880 substrate with a thickness of 0.254 mm and complete-ground on the opposite plane. The proposed MIMO 60.0 GHz EM-wave antenna offers measured impedance bandwidth of 58.925 GHz–60.66 GHz with S 11  = −35.79 dB at 59.945 GHz. The proposed MIMO 60.0 GHz technology antenna offers a peak gain of 10.56dBi at 60.0 GHz. The thin substrate is characterized for conformal bending at 15 ◦ , 30 ◦ , and 45 ◦ with no change in the center resonance frequency which is centered at 60.0 GHz. The MIMO 60.0 GHz antenna also offers good diversity performance including ECC 60.0 GHz ≤ 0.50 , DG 60.0 GHz ≅ 10.0 dB, TARC 60.0 GHz ≤ 0.0  dB, CCL 60.0 GHz ≤ 0.40 b/s/Hz and MEG port1 /MEG port1 ≅ 0.0 dB which values are under the standard-ideal values. The SAR values for single and four-port MIMO antenna corresponds to ≤ 1.60 W/Kg and all the above features of the proposed MIMO 60.0 GHz antenna make it suitable for wearable (conformal) wireless applications and future mobile users.

This paper presents the design of an ultra-compact, low-loss, multi-band bandpass filter (BPF) tailored for sub-6 GHz 5G applications. The filter is based on a half-mode substrate-integrated waveguide (HMSIW) structure integrated with metamaterial-inspired unit cells, consisting of three circular and two symmetrical serrated complementary split-ring resonators (CSRRs). This configuration enables efficient and stable wave propagation even below the HMSIW cutoff frequency. The proposed structure significantly reduces the overall footprint while supporting multiple passbands. The filter occupies a compact area of 14.1 14.1 , corresponding to less than 0.004  (with being the guided wavelength at 0.97 GHz), making it one of the smallest quad-band designs reported to date. It is highly suitable for seamless integration into wireless communication systems, including WiFi, WiMAX, WLAN, 5G, and other sub-6 GHz applications. The filter exhibits four distinct passbands centered at 0.97 GHz (0.87–1.11 GHz), 2.58 GHz (2.45–2.65 GHz), 4.5 GHz (4.05–4.6 GHz), and 5.6 GHz (5.45–5.65 GHz), with corresponding insertion (return) losses of − 0.38 dB (30 dB), − 1.1 dB (35 dB), − 0.84 dB (25 dB), and − 1.1 dB (22 dB), respectively. Additionally, the design offers reconfigurability, allowing easy adaptation to different frequency bands with minimal structural modifications. To validate the proposed concept, a prototype was fabricated and experimentally characterized. The measured results show strong agreement with simulations, confirming the efficiency and robustness of the design.

In the big data era, mode division multiplexing, as a technology for extended channel capacity, demonstrates potential in enhancing parallel data processing capability. Consequently, developing a compact, high-performance mode converter through efficient design methods is an urgent requirement. However, traditional design methodologies for these converters face significant computational complexities and inefficiencies. Addressing this challenge, this paper introduces a novel topology optimization design method for mode converters employing a Dynamic Adjustment of Update Rate (DAUR). This approach markedly reduces computational overhead, accelerating the design process while ensuring high performance and compactness. As a proof-of-concept, an ultra-compact dual-mode converter was designed. The DAUR method demonstrated an 80% reduction in computational time compared to traditional methods, while maintaining a compact design (only 1.4 μm × 1.4 μm) and an insertion loss under 0.68 dB across a wavelength range of 1525 nm to 1575 nm. Meanwhile, simulated inter-mode crosstalk remained below − 24 dB across a 40 nm bandwidth. A comprehensive comparison with traditional inverse design algorithms is presented, demonstrating our method’s superior efficiency and effectiveness. Our findings suggest that DAUR not only streamlines the design process but also facilitates exploration into more complex micro-nano photonic structures with reduced resource investment.

The deterioration of ride comfort in ultra-compact vehicles has recently become an increasing concern. Active seat suspension was proposed to improve the ride comfort of ultra-compact vehicles. An active seat suspension is a vibration control device that is easily installed. The general vibration control system of the active seat suspension is fed back to the displacement and velocity by integrating the measured seat acceleration. This control has problems, such as control delay and deviation by integration. In this study, we focused on vibration control using acceleration directly. First, we established a control model that feeds back the acceleration to terminate the error occurring in the integral process and investigated the change in vibration characteristics in the case where the feedback gain of acceleration was changed. Second, the control system was analyzed to investigate the performance of the control based on the frequency characteristics. As a result, it was confirmed that the frequency response changes when the feedback gain is changed. In acceleration feedback control, ride comfort was improved by selecting a proper feedback gain because the characteristics of frequency were changed by the gain.

In this work, a microstrip diplexer with 0.004 λg 2 (10.1 × 23 mm) overall size is designed, analyzed and fabricated. The proposed diplexer has the smallest size compared to the previously reported microstrip diplexers. The proposed diplexer has a simple and novel structure, wide flat channels and very low S 11 dB . An innovative microstrip structure based on thin coupled lines is used to design of the proposed diplexer. Since in a simple structure the possibility of manufacturing errors reduces, having a simple structure is one of its advantages. Another advantage of this diplexer is two low S 11 dB of 0.17 and 0.14 dB at the lower and upper channels. The operational frequencies of our diplexer are tuned to work at 0.9 GHz and 1.8 GHz for GSM application. It has the privileges of very compact size, simple structure, small S 11 dB , two wide fractional bandwidths (FBWs) of 21 and 24.3% and acceptable S 11 dB and isolation. Due to its two wide FBWs, the presented diplexer is suitable for broadband communication systems. We have fabricated and measured the introduced diplexer to verify the design methodology and simulation results. The obtained results of the diplexer measurement confirm the simulation.

Nanophotonic devices with high densities are extremely attractive because they can potentially merge photonics and electronics at the nanoscale. However, traditional integrated photonic circuits are designed primarily by manually selecting parameters or employing semi-analytical models. Limited by the small parameter search space, the designed nanophotonic devices generally have a single function, and the footprints reach hundreds of microns. Recently, novel ultra-compact nanophotonic devices with digital structures were proposed. By applying inverse design algorithms, which can search the full parameter space, the proposed devices show extremely compact footprints of a few microns. The results from many groups imply that digital nanophotonics can achieve not only ultra-compact single-function devices but also miniaturized multi-function devices and complex functions such as artificial intelligence operations at the nanoscale. Furthermore, to balance the performance and fabrication tolerances of such devices, researchers have developed various solutions, such as adding regularization constraints to digital structures. We believe that with the rapid development of inverse design algorithms and continuous improvements to the nanofabrication process, digital nanophotonics will play a key role in promoting the performance of nanophotonic integration. In this review, we uncover the exciting developments and challenges in this field, analyse and explore potential solutions to these challenges and provide comments on future directions in this field.

As automated driving has not yet been established, on narrow roads where there is no separation between pedestrians and vehicles, it is essential to switch to manual driving. However, when the driver turns the steering wheel from one hand to another on narrow roads, it causes steering burdens and operational errors if the steering feel or burden is not proper. Thus, this study aims to construct an active steering wheel system that provides an appropriate steering feel or burden by controlling the steering reaction torque, driving position and steering gear ratio for each driver. In this paper, we focused on and examined the driving position among these. A two-dimensional steering model that considers the size of the arms for each driver was established to evaluate steering burden. In addition, a basic study was conducted on the appropriate driving position. Then, based on the joint movements and angles calculation, the appropriate driving position that considers the size of the arms was studied by evaluating the joint power. As a result, it was found that if the steering wheel position is too close to the driver, the amount of joint movement increases, and if it is too far away, the joint movement decreases. Therefore, it was found that the appropriate steering wheel position for each driver’s arm length can be considered by using the joint power.

Optical neural networks (ONNs) offer a promising solution for high-performance, energy-efficient artificial intelligence hardware by leveraging the parallelism and speed of light. However, the large-scale implementation of ONNs remains challenging due to the bulky footprint and complex control of optical synapses. In this work, we propose and simulate a plasmonic polarized synaptic architecture that overcomes the diffraction limit and enables ultra-compact ONNs. By tuning the polarization state of incident light, the optical transmittance through each plasmonic unit can be dynamically adjusted to represent a synaptic weight. Our plasmonic structures, with features as small as 40 nm, operate well below this limit in the visible spectrum (400-750 nm). Compared with diffraction and interference-based circuit designs, our proposed method achieves a substantial reduction in synaptic density by factors of 150000-fold and 1500-fold, respectively. Furthermore, we successfully demonstrate a proof-of-concept plasmonic ONN applied to the Canadian Institute for Advanced Research—10 classes (CIFAR-10) dataset using a Visual Geometry Group network with 16 layers (VGG16) model. After training for 80 epochs, the network achieves an accuracy of 93%. The polarization-tunable plasmonics paves the way towards scalable ONNs for next-generation artificial intelligence (AI) accelerators and smart sensors.