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In modern wireless communication systems, data transmission is achieved through the collaboration of digital modulation circuits and antennas. Digital baseband signals are first modulated in terms of amplitude, frequency, and phase of the carrier wave and then transmitted directionally via antennas. However, in intra-chip environments, the performance of on-chip antennas is fundamentally constrained by micro-fabrication and integration requirements. As a result, these antennas often exhibit low gain and efficiency and are susceptible to interference among closely spaced transmission channels. To address these limitations, we propose a digital coding metamaterial for direct signal modulation within intra-chip wireless channels, providing an alternative solution to achieve directional signal delivery without depending on the antenna’s intrinsic radiation pattern. The proposed metamateiral can directly convert digital control inputs into discrete phase shifts of a 70 GHz TE-mode surface wave, enabling post-radiation modulation as the electromagnetic wave propagates through the metamaterial. When combined with a single broadcast antenna, multiple metamaterial units can perform simultaneous, multi-directional modulation and transmissions. The proposed metamaterial supports various phase shift modulation schemes, including BPSK, QPSK, and 8-PSK. Furthermore, it enables hybrid modulation and beam steering modes, offering a beam steering range of up to$$\\pm 28^{\\circ }$$. The proposed metamateiral presents an innovative method for information routing in intra-chip transmission, helps reduce signal crosstalk under parallel transmission, and expands wireless channel capacity and spectral efficiency.

Achromatic metalenses, planar diffractive devices structured with subwavelength nanostructures, are central to the development of compact, integrable alternatives to bulky multi-element optics. Yet their progress is fundamentally constrained by chromatic dispersion, which imposes trade-offs among operational bandwidth, numerical aperture (NA), aperture size, and efficiency. In this review, we introduce a unified framework that classifies achromatization strategies into four distinct paradigms: dispersion engineering, algorithm-aided method, architecture modification, and wavefront engineering. For each category, we analyze the underlying mechanisms, performance trade-offs, and fabrication limits, while identifying opportunities for cross-strategy synergies. Building on this framework, we highlight a forward-looking challenge: the realization of high-efficiency, centimeter-scale broadband achromatic metalenses from visible to infrared, an essential milestone toward application-ready flat optical systems in imaging, sensing, and augmented/virtual reality. This classification and roadmap aim to guide future efforts in overcoming long-standing bottlenecks of dispersion, scalability, and manufacturability.

A method based on equal frequency resampling is proposed to suppress laser nonlinear frequency sweeping for the ultimate spatial resolution in optical frequency domain reflectometry. Estimation inaccuracy of the sweeping frequency distribution caused by the finite sampling rate in the auxiliary interferometer can be efficiently compensated by the equal frequency resampling method. With the sweeping range of 130 nm, a 12.1 µm spatial resolution is experimentally obtained. In addition, the sampling limitation of the auxiliary interferometer-based correction is discussed. With a 200 m optical path delay in the auxiliary interferometer, a 21.3 µm spatial resolution is realised at the 191 m fibre end. By employing the proposed resampling and a drawing tower FBG array to enhance the Rayleigh backscattering, a distributed temperature sensing over a 105 m fibre with a sensing resolution of 1 cm is achieved. The measured temperature uncertainty is limited to ±0.15 °C.

Light Detection and Ranging (LiDAR) sensors can precisely determine object distances using the pulsed time of flight (TOF) or amplitude-modulated continuous wave (AMCW) TOF methods and velocity using the frequency-modulated continuous wave (FMCW) approach. In this paper, we focus on modelling and analysing the reflection of vector beams (VBs) and vector vortex beams (VVBs) for optical sensing in LiDAR applications. Unlike traditional TOF and FMCW methods, this novel approach uses VBs and VVBs as detection signals to measure the orientation of reflecting surfaces. A key component of this sensing scheme is understanding the relationship between the characteristics of the reflected optical fields and the orientation of the reflecting surface. To this end, we develop a computational model for the reflection of VBs and VVBs. This model allows us to investigate critical aspects of the reflected field, such as intensity distribution, intensity centroid offset, reflectance, and the variation of the intensity range measured along the azimuthal direction. By thoroughly analysing these characteristics, we aim to enhance the functionality of LiDAR sensors in detecting the orientation of reflecting surfaces.

This paper presents the total angular momentum-conserving Poincaré sphere (TAM-C PS), which offers a novel framework for efficiently characterizing a wide range of vector vortex beams. Unlike other types of Poincaré spheres, the TAM-C PS achieves a better balance between generality and validity, while also providing clearer physical interpretation. By linking the poles of different spheres, the study also introduces two distinct categories of TAM-C PS braid clusters, enabling the representation of various Poincaré spheres within a unified framework. The Poincaré spheres include classical, higher-order, hybrid-order, Poincaré sphere with orbital angular momentum, and TAM-C PS. This is the first clear and unified approach to express multiple Poincaré spheres within a single framework. The TAM-C PS and its braid cluster can be employed to guide the creation of targeted vector vortex light beams, offer a geometric description of optical field evolution, and calculate the geometric phase of optical cyclic evolution.

Metasurfaces offer compact, lightweight alternatives to conventional optics by enabling precise wavefront control with subwavelength nanostructures. However, the mechanical fragility of pillar‐based configurations limits their applicability in practical systems, particularly under routine handling and cleaning. Here, we report a mechanically robust metasurface architecture in which high refractive index nanopillars are encapsulated within a conformal SiO2 layer. Numerical simulations indicate that the embedded design maintains stable focusing efficiency over a wide range of surrounding refractive index values of common operational media such as air, water, and oil, whereas pillar‐based structures exhibit significant degradation. Experimentally, the embedded design preserves diffraction‐limited focusing and high‐contrast imaging performance. After standard mechanical cleaning, the embedded metasurface maintains over 90% of its initial focusing efficiency, while unprotected metasurfaces exhibit an efficiency reduction of approximately 88%. The near‐symmetric dielectric layer enhances orientation‐independent optical response, demonstrating identical imaging performance under forward and reverse illumination. A magnification ratio of 1.29 is observed between two configurations. This ratio arises from the difference in object distances, which is caused by the thickness differences in the substrate and the encapsulated SiO2 layer. This CMOS‐compatible, bidirectional, and mechanically stable metasurface platform provides a scalable approach to integrated flat optics for advanced imaging and sensing applications. A mechanically robust metasurface is developed by embedding high‐index nanopillars within a conformal SiO2 layer. The design retains stable focusing efficiency, diffraction‐limited imaging, and bidirectional operation, while withstanding routine mechanical cleaning, enabling durable and CMOS‐compatible flat optics for practical applications.

An optically levitated nanoparticle in a vacuum provides an ideal platform for ultra-precision measurements and fundamental physics studies because of the exceptionally high-quality factor and rich motion modes, which can be engineered by manipulating the optical field and the geometry of the nanoparticle. Nanofabrication technology with the ability to create arbitrary nanostructure arrays offers a precise way of engineering the optical field and the geometry of the nanoparticle. Here, for the first time, we optically levitate and rotate a nanofabricated nanorod via a nanofabricated a-Si metalens which strongly focuses a 1550 nm laser beam with a numerical aperture of 0.953. By manipulating the laser beam’s polarization, the levitated nanorod’s translation frequencies can be tuned, and the spin rotation mode can be switched on and off. Then, we showed the control of rotational frequency by changing the laser beam’s intensity and polarization as well as the air pressure. Finally, a MHz spin rotation frequency of the nanorod is achieved in the experiment. This is the first demonstration of controlled optical spin in a metalens-based compact optical levitation system. Our research holds promise for realizing scalable on-chip integrated optical levitation systems.

Optically levitated multiple nanoparticles have emerged as a platform for studying complex fundamental physics such as non-equilibrium phenomena, quantum entanglement, and light–matter interaction, which could be applied for sensing weak forces and torques with high sensitivity and accuracy. An optical trapping landscape of increased complexity is needed to engineer the interaction between levitated particles beyond the single harmonic trap. However, existing platforms based on spatial light modulators for studying interactions between levitated particles suffered from low efficiency, instability at focal points, the complexity of optical systems, and the scalability for sensing applications. Here, we experimentally demonstrated that a metasurface which forms two diffraction-limited focal points with a high numerical aperture (∼0.9) and high efficiency (31 %) can generate tunable optical potential wells without any intensity fluctuations. A bistable potential and double potential wells were observed in the experiment by varying the focal points’ distance, and two nanoparticles were levitated in double potential wells for hours, which could be used for investigating the levitated particles’ nonlinear dynamics, thermal dynamics and optical binding. This would pave the way for scaling the number of levitated optomechanical devices or realizing paralleled levitated sensors.

Short-Time Fourier Transform-Brillouin Optical Time-Domain Reflectometry (STFT-BOTDR) implements STFT over the full frequency spectrum to measure the distributed temperature and strain along the optic fiber, providing new research advances in dynamic distributed sensing. The spatial and frequency resolution of the dynamic sensing are limited by the Signal to Noise Ratio (SNR) and the Time-Frequency (T-F) localization of the input pulse shape. T-F localization is fundamentally important for the communication system, which suppresses interchannel interference (ICI) and intersymbol interference (ISI) to improve the transmission quality in multicarrier modulation (MCM). This paper demonstrates that the T-F localized input pulse shape can enhance the SNR and the spatial and frequency resolution in STFT-BOTDR. Simulation and experiments of T-F localized different pulses shapes are conducted to compare the limitation of the system resolution. The result indicates that rectangular pulse should be selected to optimize the spatial resolution and Lorentzian pulse could be chosen to optimize the frequency resolution, while Gaussian shape pulse can be used in general applications for its balanced performance in both spatial and frequency resolution. Meanwhile, T-F localization is proved to be useful in the pulse shape selection for system resolution optimization.

The conventional resonant-approaches to scavenge kinetic energy are typically confined to narrow and single-band frequencies. The vibration energy harvester device reported here combines both direct resonance and parametric resonance in order to enhance the power responsiveness towards more efficient harnessing of real-world ambient vibration. A packaged electromagnetic harvester designed to operate in both of these resonant regimes was tested in situ on the Forth Road Bridge. In the field-site, the harvester, with an operational volume of ∼126 cm3, was capable of recovering in excess of 1 mW average raw AC power from the traffic-induced vibrations in the lateral bracing structures underneath the bridge deck. The harvester was integrated off-board with a power conditioning circuit and a wireless mote. Duty- cycled wireless transmissions from the vibration-powered mote was successfully sustained by the recovered ambient energy. This limited duration field test provides the initial validation for realising vibration-powered wireless structural health monitoring systems in real world infrastructure, where the vibration profile is both broadband and intermittent.