arXiv subjects

Weimin Deng

Publications and source records attributed to Weimin Deng.

4 recordsLinked to original sources

arXiv2026

Valley-locked Optical Spin Merons in Valley Photonic Crystal Waveguides

Optical skyrmionic textures, including N\'eel-type skyrmions and merons, have attracted significant attention across diverse physical systems for their promising applications in ultra-precise metrology, optical information processing, and quantum technologies. However, the lack of an effective approach for their on-chip directional transport and manipulation impedes their applications in photonic integrated devices. Here, we numerically demonstrate a photonic platform that utilizes topologically protected valley edge state to achieve robust on-chip directional transport of optical spin merons. These merons originate from spin-orbit coupling within the evanescent field at the valley photonic crystal surface and exist as eigenstates of the topologically protected edge state, ensuring their robust propagation even in the interface with defects. Leveraging the valley degree of freedom of topological edge states, we further achieve valley-locked spin merons, enabling flexible control over the polarity of spin merons. By endowing spin merons with topological protection in momentum space, our work provides an approach for robust on-chip transport and manipulation of spin merons, thereby paving the way for expanding their application in photonic systems.

physics.optics↗

arXiv2024

Spin-orbit interactions of the twisted random light

The twist phase of random light represents a nontrivial two-point phase, endowing the field with orbital angular momentum. Although the mutual transition of the spin and orbit angular momenta of coherent light has been revealed, the relationship between spin-orbital angular momentum interaction (SOI) and the twist phase has remained unexplored. This is because of the stochastic nature of random light, making it challenging to explore the properties of angular momenta that rely on well-defined spatial and polarization structures. This study addresses this gap from the view of the asymmetry coherent-mode decomposition for twisted random light to gain insight into the intricate interplay between the twist phase and the SOI within a tight focusing system. Our findings reveal that spin and orbit angular momentum transitions occur in the tightly focused twisted random light beam, yielding the transverse spin density controlled by the twist phase. This effect becomes more pronounced when the spin of random light and the chirality of the twist phase are the same. Our work may find significant applications in optical sensing, metrology, and quantum optics.

physics.optics↗

arXiv2024

Observation of Moir\'e Plasmonic Skyrmion Clusters

Skyrmions are topological defects belonging to nontrivial homotopy classes in particle theory. Their remarkably stable topology has recently been observed in electromagnetic waves. For the evanescent fields near a surface, this has been realized so far only for elementary optical skyrmions, with a fixed skyrmion number. Here we report, both in theory and experiment, the concept of moir\'e plasmonic skyrmion clusters, where multi-skyrmions are nested to form a large optical skyrmion cluster. By leveraging twistronics engineering of plasmonic nanostructures, we demonstrate both crystallized and quasi-crystallized optical skyrmion lattices, revealing an unprecedented degree of topological control. In a misaligned composite nanostructure, the rapid inverting of optical skyrmion number is achieved, which is explained by a lattice model. This topological change of moir\'eplasmonic skyrmion clusters can serve as a precise beacon of the relative alignment deviation between composite nanostructures.

physics.optics↗

arXiv2024

Extremely intrinsic chirality in two-dimensional planar waveguide grating induced by quasi-bound states in the continuum

The strong chiral light-matter interaction is crucial for various important fields such as chiral optics, quantum optics, and biomedical optics, driving a quest for the extreme intrinsic chirality assisted by ultrahigh quality ($Q$-) factor resonances. In this quest, we propose a straightforward method to achieve extreme intrinsic chirality in lossless planar structures by manipulating the quasi-BIC through in-plane perturbation. The temporal coupled-mode theory is employed to derive the conditions necessary for achieving maximal intrinsic chirality. The quasi-BIC should be excited within the transparent spectral range of the structure and couple with $x$- and $y$-polarized waves with the same intensity but a phase difference of $π$/2. For an illustration, a planar chiral dielectric dimeric waveguide grating is designed that strong interacts with left circularly polarized (LCP) light while decouples from right circularly polarized (RCP) light through in-plane symmetry engineering. Furthermore, by adjusting the magnitude of the in-plane asymmetry, we can independently manipulate the $Q$-factors of the chiral quasi-BIC while maintaining nearly unity circular dichroism. Our results provide a simple yet powerful paradigm for achieving extreme intrinsic chirality on an easily manufacturable platform, which may have potential applications in chiral emission, chiral sensing, and enantiomer separation.

physics.optics↗