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Abstract Optical vortices have the tremendous potential to increase data capacity by leveraging the extra degree of freedom of orbital angular momentum. On the other hand, anisotropic 2D materials are promising building blocks for future integrated polarization‐sensitive photonic and optoelectronic devices. Here, highly anisotropic third‐harmonic optical vortex beam generation is demonstrated with fork holograms patterned on ultrathin 2D germanium arsenide flakes. It is shown that the anisotropic nonlinear vortex beam generation can be achieved independent of the fork grating orientation with respect to the crystallographic orientation. Furthermore, 2D fork hologram is designed to generate multiple optical vortices having different topological charges with strong anisotropic responses. These results pave the way toward the advancement of 2D material‐based anisotropic nonlinear optical devices for future applications in photonic integrated circuits, optical communication, and optical information processing. 

Abstract Detection and identification of chiral molecules are important for pharmaceutical industry, clinical analysis, and food analysis. Here, chiral molecular sensing based on spatially selective coupling between achiral metasurface and chiral molecules is demonstrated. The designed achiral metasurface exhibits strong optical chirality and electric field with dissymmetric distribution, and chiral molecules are selectively placed over the area with large optical chirality to form the coupled metasurface-molecule system with circular dichroism (CD) response for chiral molecular sensing. The CD spectra of the metasurface coupled with pure D-alanine enantiomer, L-alanine enantiomer and their mixtures are examined. The linear relationship between the peak CD value and the enantiomeric excess is demonstrated for the detection and identification of pure enantiomers and their mixtures. Furthermore, the CD response of the coupled system shows potential for the sensing of molar concentration of chiral molecules. Moreover, the effect of spatial location of molecules on the CD response is analyzed to show potential for position sensing of chiral molecules. These results of chiral molecular sensing with achiral metasurface offer new opportunities for advancing biomolecular sensing applications. 

Achiral metasurfaces with near-field optical chirality have attracted great attention in molecular sensing and chiral emission control. Here, the circular dichroism (CD) response of an achiral metasurface induced by spatially selective coupling with polymethyl methacrylate (PMMA) molecules is demonstrated. A designed achiral metasurface with a V-shaped resonator exhibits large optical chirality with a strongly dissymmetric distribution under circular polarization. By introducing a PMMA molecule layer on top of the metasurface, which covers the area with large optical chirality, CD in absorption of 0.38 and a dissymmetric factor of optical chiralityg_cof 0.16 are obtained. Furthermore, an analysis of the coupled harmonic oscillator model reveals stronger coupling strength between the PMMA layer and the metasurface under RCP incidence, compared to the LCP case. Moreover, it is shown that the far-field CD response of the metasurface is linearly correlated with the dissymmetric near-field optical chirality distribution. The demonstrated results present the potential for advancing applications in chiral molecule vibrational sensing, thermal emission control, and infrared chiral imaging. 

To deal with distribution shifts in graph data, various graph out-of-distribution (OOD) generalization techniques have been recently proposed. These methods often employ a two-step strategy that first creates augmented environments and subsequently identifies invariant subgraphs to improve generalizability. Nevertheless, this approach could be suboptimal from the perspective of consistency. First, the process of augmenting environments by altering the graphs while preserving labels may lead to graphs that are not realistic or meaningfully related to the origin distribution, thus lacking distribution consistency. Second, the extracted subgraphs are obtained from directly modifying graphs, and may not necessarily maintain a consistent predictive relationship with their labels, thereby impacting label consistency. In response to these challenges, we introduce an innovative approach that aims to enhance these two types of consistency for graph OOD generalization. We propose a modifier to obtain both augmented and invariant graphs in a unified manner. With the augmented graphs, we enrich the training data without compromising the integrity of label-graph relationships. The label consistency enhancement in our framework further preserves the supervision information in the invariant graph. We conduct extensive experiments on real-world datasets to demonstrate the superiority of our framework over other state-of-the-art baselines. 

Visible-light-driven N-centered radicals lead to C-centered α-amino radicals through rare net-1,2-HAT processes, with trapping by silyl enol ethers to access β-amido ketone derivatives. 

Integrating phase-change materials in metasurfaces has emerged as a powerful strategy to realize optical devices with tunable electromagnetic responses. Here, phase-change chiral metasurfaces based on GST-225 material with the designed trapezoid-shaped resonators are demonstrated to achieve tunable circular dichroism (CD) responses in the infrared regime. The asymmetric trapezoid-shaped resonators are designed to support two chiral plasmonic resonances with opposite CD responses for realizing switchable CD between negative and positive values using the GST phase change from amorphous to crystalline. The electromagnetic field distributions of the chiral plasmonic resonant modes are analyzed to understand the chiroptical responses of the metasurface. Furthermore, the variations in the absorption spectrum and CD value for the metasurface as a function of the baking time during the GST phase transition are analyzed to reveal the underlying thermal tuning process of the metasurface. The demonstrated phase-change metasurfaces with tunable CD responses hold significant promise in enabling many applications in the infrared regime such as chiral sensing, encrypted communication, and thermal imaging.