Chunyu Song

To satisfy the demand for high-precision online monitoring of early signature gases, carbon dioxide (CO2) and carbon monoxide (CO), in lithium-ion battery thermal runaway, we propose a multi-component gas sensing system based on a Convolutional Neural Network (CNN) via Cross-Architecture Knowledge Distillation (CAKD). Prior knowledge learned by the teacher model from noisy second harmonic (2ƒ) signals is distilled into a structurally simpler student model, reducing inference latency and computational burden. Under laboratory conditions, the system achieved concentration fitting accuracies of 0.9997 for CO2 and 0.9990 for CO. The mean absolute errors (MAE) for CO2 and CO were 62.615 and 30.110 ppm, respectively, and the mean relative errors (MRE) were 0.500% and 1.759%. Allan deviation analysis further yields detection limits of 3.1171 ppm for CO2 at an averaging time of 146 s and 1.6604 ppm for CO at 122 s. Deployed on a Raspberry Pi, the system achieved an average per-sample inference time of 0.2037 ms, satisfying real-time online monitoring requirements. The model parameter count and computational cost were reduced by 88.47% and 94.10%, respectively, compared with the teacher model. The sensor was further applied to real-time monitoring of CO2 and CO during lithium-ion battery thermal runaway, successfully identifying characteristic gas signals 874 s before thermal runaway onset. These results demonstrate that CAKD significantly reduces model complexity and inference latency while maintaining accurate trace gas detection, demonstrating its application value in embedded safety monitoring systems.

Tunable manipulation of focused vector vortex beams (FVVBs) in the terahertz (THz) regime is highly desirable for advanced applications in imaging, sensing, and communications, yet conventional methods often suffer from limited reconfigurability and integration capacity. In this work, we propose a dynamic metasurface platform enabling in-plane scanning of FVVBs through moiré phase engineering in two cascaded, rotatable all-silicon metasurfaces. Each layer is meticulously designed with decomposed phase profiles, combining spiral, gradient, and lens phases, to independently manipulate orthogonal circular polarization (CP) channels. By mechanically rotating the metasurfaces, we numerically demonstrate continuous lateral displacement of the focused vector beam within the focal plane, with negligible variation in focal length and robust performance under inter-layer separation changes. Furthermore, simultaneous rotation of both layers allows arbitrary positioning of the focal spot and tailored polarization symmetry. This strategy offers a versatile and compact solution for dynamic wavefront control, paving the way for adaptive THz systems with high integration capabilities.

Multifunctional photodetectors require the photosensitive layer to exhibit both broad spectral response and high‐performance characteristics. Silicon‐based photodetectors are widely applied, benefiting from high quantum efficiency and mature fabrication processes. However, the silicon bandgap of over 1 eV limits its operational range across a broad spectrum. In this study, a semimetal‐controlled, silicon‐based broadband photodetector is developed, in which the semimetal ZrTe ₃ functions as both the barrier control layer and the light absorption layer. The results demonstrate that the designed silicon photodetector achieves an ultra‐broad spectral response ranging from ultraviolet to mid‐infrared (355 nm to 3.35 µm). With its high responsivity and ultrafast response time, a single‐pixel imaging module and a low‐concentration gas sensing module are further developed. The imaging module can capture clear contours at a sampling rate as low as 1%, highlighting its significant potential in computational optics. The gas sensing module detects CH ₄ with a lower detection limit of 5.35 ppm in the near‐infrared and successfully demonstrates stable gas detection capabilities in the prototype.

Next‐generation photodetectors demand multidimensional information perception, high responsivity, and low noise equivalent power across an ultra‐wide spectral range. Polarization‐sensitive photodetectors based on anisotropic low‐dimensional materials offer a promising solution, yet inherent material properties impose severe performance trade‐offs. Here, this challenge is addressed by developing an ultra‐broadband polarization photodetector with back‐to‐back Schottky barriers, fabricated via UV laser treatment of semi‐metallic ZrTe ₃ . The results demonstrate that the ZrTe ₃ polarization photodetector achieves ultra‐wide spectral polarized light response from UV to terahertz (355 nm–1.43 mm) with antenna‐free integration at room temperature. Notably, it exhibits a high responsivity of 0.31 A W ⁻¹ with rise/fall times of 729 ns/14.9 µs at 532 nm. One‐year‐long photoresponse tests in air demonstrate stability for ultra‐broadband ZrTe ₃ polarization detector (UBPD). This work highlights the transformative potential of ZrTe ₃ for future wide‐spectrum polarization‐sensitive applications.

Moiré meta-devices facilitate continuous and precise modulation of optical properties through the alteration of the relative alignment, such as twisting, sliding, or rotating of the metasurfaces. This capability renders them particularly suitable for dynamic applications, including zoom optics and adaptive imaging systems. Nevertheless, such designs often sacrifice more complex functionalities, such as polarization manipulation, in favor of simplicity and tunability. Here, we propose and experimentally validate a design strategy for a twisted bilayer metasurface that exhibits both varifocal capabilities and polarization filtering properties. By selecting silicon pillars with polarization-maintaining properties for Layer I and polarization-converting properties for Layer II, the designed Moiré metasurface can become sensitive to specific polarization states. Experimental results demonstrate that the proposed design can generate on-demand terahertz (THz) focused beams, achieving an average focusing efficiency exceeding 35% under x-linearly polarized (x-LP) illumination. This is accomplished by systematically varying the twisting angles p and q of Layer I in relation to Layer II in increments of 30°. Additionally, we provide numerical evidence that the focal length of the transmitted vortex beam can be adjusted using the same approach. The Moiré meta-device platform, which is engineered to modulate optical properties via mechanical twisting, obviates the necessity for external power sources or active materials. This generalized design strategy has the potential to significantly expedite the commercialization of multifunctional metasurfaces, which can produce high-precision optics across various practical applications.

In response to the growing demands of advanced 5G/6G communication technologies, millimeter-wave vortex beams have emerged as a promising solution to increase channel capacities. This paper introduces a novel and efficient method for vortex beam generation by leveraging the intrinsic singularities of dipole scatterers and enhancing their performance through non-local coupling. We demonstrate that the intrinsic singularities—amplitude-zero points in the scattering patterns of electric dipole (ED) and magnetic dipole (MD) resonances – enable the conversion of spin angular momentum (SAM) into orbital angular momentum (OAM), generating a vortex electric field distribution. By arranging these dipolar units into a periodic array, we establish a dual-resonance non-local metasurface that improves directivity and efficiency via non-local collective interactions and the generalized Kerker effect. This configuration significantly enhances forward scattering, producing highly directional vortex beams. Our experimental results show that the non-local metasurface achieves a vortex conversion efficiency approximately 2.2 times higher than that of a reference structure around 40 GHz. This alignment-free, high-efficiency solution offers great potential for expanding millimeter-wave communication capacity and advancing photonic applications.

Waveplates provide precise control over the state of polarization and are essential components in various technologies and scientific disciplines, greatly enhancing the performance of optical systems. Recently, advancements in metasurface technology have enabled the miniaturization of bulky optical components that manipulate polarization states while mitigating insertion loss. Nevertheless, generating vortex beams with specific topological charges within the desired polarization channels remains a significant challenge when utilizing versatile metasurface-based wave plates. This work presents a generalized design strategy for multifunctional metasurfaces, demonstrated through simulations and experiments, by varying the parametric conditions that facilitate the spin decoupling mechanism. Independent encoding of spin-polarized channels is achieved by integrating both geometric and propagation phase profiles into silicon pillar designs that exhibit birefringent effects. Meta-waveplates designed for operator computational mechanisms can effectively exhibit the behavior of orbital coupling from spin angular momentum (SAM) to orbital angular momentum (OAM) within a predetermined polarization channel. Also, OAM beams with topological charge evolution behavior in the longitudinal direction are further demonstrated, effectively enhancing the design freedom of multifunctional meta-waveplates. This research paves the way for developing multifunctional, high-performance, and ultra-compact terahertz meta-devices.