Khian-Hooi Chew

Oxygen-doped 2D GaN strongly anchors lithium polysulfides and enhances sulfur reduction kinetics in Li–S batteries.

The reconstruction and manipulation of an optical field passing through a scattering medium have attracted significant attention. The generation and manipulation of vector beams with arbitrary non-uniform polarization-state using a highly anisotropic scattering medium (HASM) remain a challenging topic. Here, a high-resolution vector light field with an arbitrary polarization state over a highly scattering medium is generated by employing an extended polarization transfer matrix (EPTM) for more intuitive and convenient manipulation of the polarization state of output light. To our knowledge, this is the first time that EPTMs have been used to achieve the superposition of non-orthogonal polarization states with diverse energy-weight ratios through polarization-multiplexing each polarization component of the input field and intermodal phase adjustments between polarized light components after passing through HASM. These findings improve our understanding of the HASM’s vector manipulation capabilities regarding non-uniformly polarized light and may have potential applications in relevant fields.

Material recognition of targets plays a crucial role in various applications, including autonomous systems, industrial inspection, augmented reality, and remote sensing. However, it presents a persistent challenge for computer vision systems, which often fail to distinguish materials, especially in complex scenes, accurately. In this work, the polarization features of reflected light from the target are analyzed, and the degree of linear polarization (DOLP) is leveraged to identify the material of the targets. A polarization-guided material recognition network (PMRNet) is proposed to enhance material recognition by leveraging the DOLP of reflected light from targets. PMRNet comprises a polarization feature aggregation diffusion network, which enhances the feature representation capability and reduces the information loss by multiscale feature fusion. It also includes a polarization sharing detection head that enables material recognition of targets through fusing cross-polarization features. Experimental results demonstrate the effectiveness and robustness of the proposed method with better evaluation indicators compared with other material recognition methods. Only the DOLP information as input can effectively reduce the complexity of the network and enhance the robustness of the network. In complex scenes, the DOLP contributes more significantly to accurate material recognition than polarization angle and intensity features, underscoring the value of DOLP polarimetric information for distinguishing materials under challenging conditions.

In this study, we demonstrate both theoretically and experimentally second harmonic generation (SHG) of a twisted vector vortex optical field (TVVOF) using a nonlinear type-II phase-matched β-BaB₂O₄ (BBO) crystal. Our study introduces a novel method to manipulate SHG by independently modulating the two orthogonal polarization components of a TVVOF. This flexibility in controlling SHG can be achieved through accurate experimental adjustments of the polarization components. Furthermore, we reveal that the SHG can be dynamically tuned by varying the angle between the polarization direction of the optical field and the principal axis of the BBO crystal via rotation. These findings provide a new approach for the flexible manipulation of SHG in structured vector optical fields, which have potential applications in optical communication, quantum optics, and photonic device engineering.

Based on the two-dimensional (2D) nonlinear Schrödinger equation, we investigate the collapse dynamics of a vector vortex optical field (VVOF) in nonlinear Kerr media with parity–time (PT)-symmetric modulation. The critical power for the collapse of a VVOF in a Kerr-ROLP medium (Kerr medium with a real optical lattice potential) is derived. Numerical simulations indicate that the number, position, propagation distance, and collapse profile of the collapse of a VVOF in sine and cosine parity–time-symmetric potential (SCPT) Kerr media are closely related to the modulation depth, initial powers, and the topological charge number of a VVOF. The VVOF collapses into symmetric shapes during propagation in a Kerr-ROLP medium, and collapse shapes are sensitively related to the density of the PT-symmetric optical lattice potential. In addition, due to gain–loss, the VVOF will be distorted during propagation in the Kerr-SCPT medium, forming an asymmetric shape of collapse. The power evolution of the VVOF in a Kerr-SCPT medium as a function of the transmission distance with different modulating parameters and topological numbers is analyzed in detail. The introduction of PT-symmetric optical lattice potentials into nonlinear Kerr materials may provide a new approach to manipulate the collapse of the VVOF.

Underwater target detection is an essential topic in the applications of underwater exploration. However, underwater target detection faces serious challenges, such as complex scattering, low visibility, and target clutter. Here a polarization-enhanced underwater multiple material target detection method is proposed to address these challenges. The similarity principle of locally backscattered polarization features is utilized to suppress the influence of backscattered light. Our target detection model combines polarization gradient and edge detection techniques to optimize the detection process, enabling superior target detection and feature extraction. Experimental results indicate that our method has significantly enhanced the detection performance in multiple (overlapping or nonoverlapping) material targets, especially in high turbid underwater scattering environments. This research provides a promising new approach for polarized target detection in underwater environments and opens up new possibilities for underwater multiple-material target detection.

This study investigates the influence of high-order twisting phases on polarization states and optical angular momentum of a vector light field with locally linear polarization and a hybrid state of polarization (SoP). The twisted vector optical field (TVOF) is experimentally generated based on the orthogonal polarization bases with high-order twisting phases. The initial SoP of a TVOF modulated by the high-order twisting phase possesses various symmetric distributions. The propagation properties of a high-order TVOF with locally linear polarization and hybrid SoP are explored, including the intensity compression, expansion, and conversion between the linear and circular polarization components. In particular, orbital angular momentum (OAM) appears in a high-order TVOF during propagation where no OAM exists in the initial field. The variation of OAM distribution in cross-section becomes more frequent with the increase of the twisting phase order. In addition, a non-symmetric OAM distribution appears in a non-isotropic TVOF, leading to the rotation of the beam around the propagation axis during propagation. The optical energy flow distribution of a high-order TVOF provides a more profound understanding of the propagation dynamics of high-order TVOF. These results provide a new approach for optical field manipulation in a high-order TVOF.

We study the influence of high-order twisting phases on polarization states and optical angular momentum of a vector light field with locally linear polarization and a hybrid state of polarization (SoP). The initial SoP of a twisted vector optical field (TVOF) modulated by the high-order twisting phase possesses various symmetric distributions. The propagating properties of a high-order TVOF with locally linear polarization and hybrid SoP are explored, including the intensity compression, expansion, and conversion between the linear and circular polarization components. In particular, orbital angular momentum (OAM) appears in a high-order TVOF during propagation where no OAM exists in the initial field. The variation of OAM distribution in cross-section becomes more frequent with the increase of the twisting phase order. In addition, a non-symmetric OAM distribution appears in an anisotropic TVOF, leading to the rotation of the beam around the propagation axis during propagation. These results provide a new approach for optical field manipulation in a high-order TVOF.