Graphene is an ideal ultrathin material for various optoelectronic devices, but poor light–graphene interaction limits its further applications particularly in the visible (Vis) to near-infrared (NIR) region. Despite tremendous efforts to improve light absorption in graphene, achieving highly efficient light absorption of monolayer graphene within a comparatively simple architecture is still urgently needed. Here, we demonstrate the interesting attribute of bound state in the continuum (BIC) for highly efficient light absorption of graphene by using a simple Si-based photonic crystal slab (PCS) with a slit. Near-perfect absorption of monolayer graphene can be realized due to high confinement of light and near-field enhancement in the Si-based PCS, where BIC turns into quasi-BIC due to the symmetry-breaking of the structure. Theoretical analysis based on the coupled mode theory (CMT) is proposed to evaluate the absorption performances of monolayer graphene integrated with the symmetry-broken PCS, which indicates that high absorption of graphene is feasible at critical coupling based on the destructive interference of transmission light. Moreover, the absorption spectra of the monolayer graphene are stable to the variations of the structural parameters, and the angular tolerances of classical incidence can be effectively improved via full conical incidence. By using the full conical incidence, the angular bandwidths for the peak absorptivity and for the central wavelength of graphene absorption can be enhanced more than five times and 2.92 times, respectively. When the Si-based PCS with graphene is used in refractive index sensors, excellent sensing performances with sensitivity of 604 nm/RIU and figure of merit (FoM) of 151 can be achieved.

An angle-insensitive broadband absorber of graphene covering the whole visible spectrum is numerically demonstrated, which is resulted from multiple couplings of the electric and magnetic dipole resonances in the narrow metallic grooves. This is achieved by integrating the graphene sheet with a multi-grooved metasurface separated by a polymethyl methacrylate (PMMA) spacer, and an average absorption efficiency of 71.1% can be realized in the spectral range from 450 to 800 nm. The location of the absorption peak of graphene can be tuned by the groove depth, and the bandwidth of absorption can be flexibly controlled by tailoring both the number and the depth of the groove. In addition, broadband light absorption enhancement of graphene is robust to the variations of the structure parameters, and good absorption properties can be maintained even the incident angle is increased to 60°.

High‐Q resonances in metasurfaces, stemming from symmetry‐protected bound states in the continuum (BICs), have proven to be effective for achieving high‐performance optical devices. However, the properties associated with symmetry‐protected BICs are inherently limited, as even a slight variation in the asymmetry parameter leads to a noticeable shift in the resonance location. Herein, we introduce the concept of relative shift–induced quasi‐BICs (QBICs) within dimerized silicon (Si) meta‐lattices (DSMs), which can be excited when a nonzero relative shift occurs, a result of in‐plane inversion symmetry breaking and Brillouin zone folding within the structure. These QBICs have resonance locations that remain insensitive to variations in asymmetrical parameters. Additionally, their Q‐factors can be flexibly tuned, benefiting from the inverse square dependence on asymmetrical parameters. In experiment, six DSMs with different relative shifts are fabricated and the asymmetry parameter‐insensitive resonant modes under two orthogonal polarization states are experimentally observed in the optical communication waveband. Our results offer unique opportunities for constructing high‐Q resonators with enhanced performances, which can be applied in various optical fields.

Chiral quasi-bound states in the continuum (QBIC) offer novel mechanisms to achieve intrinsic chiroptical responses. However, current studies on chiral QBIC metasurfaces are restricted to the excitation of intrinsic chirality and fail to dynamically control its circular dichroism (CD) responses. Herein, we construct a phase-change metasurface based on paired Ge₂Sb₂Te₅ (GST) bars to demonstrate the dynamic control of the CD responses of chiral QBIC. The modified coupled mode theory (CMT) is proposed to evaluate the intrinsic chirality, and the predicted results are in good agreement with the finite–difference time-domain (FDTD) results. The maximal intrinsic chirality is associated with the spin-selected dipole mode, i.e., the coupled magnetic dipole (MD) QBIC mode for the left-handed circularly polarized (LCP) light and the decoupled electric dipole (ED) QBIC mode for the right-handed circularly polarized (RCP) light. By varying the volume fraction of GST, the location of chiral BIC can be tuned linearly, and the corresponding chiral response can be switched.

Optical vortex beam carrying orbit angular momentum has been extensively researched and applied recently. Among which a perfect vortex beam (PVB) has attracted much attention owing to its topological charge (TC)-irrelevant intensity profile. However, the morphology singularity, as well as implementation complexity of the PVB tie the degree of freedom for multiplexing. Herein, by introducing the concept of a composite vortex beam, we originally propose a novel kind of PVB – perfect composite vortex beam (PCVB) – which possesses a rosette-like intensity pattern that is exactly correlated with the TC and can be directly generated using a single all-dielectric geometric metasurface rather than bulky optical systems. We numerically simulate the broadband generation of the proposed PCVB with various TCs, sizes, and rotation angles. To further explore the potential of our design in practical applications, we demonstrated the coaxial array of the PCVBs and detected their optical angular force for manipulating nanoparticles. We believe that our fruitage may pave a desirable avenue for optical communication, information processing, and optical manipulation.

A hybrid structure of graphene ribbons suspended on grooves of a periodic SiC grating is proposed. Magnetic polaritons in the SiC grating can couple with surface plasmons in graphene ribbons. The field distributions obtained from COMSOL simulation, in agreement with the prediction from a LC circuit model, strongly indicate that magnetic polaritons can be excited in the SiC grating. We find that the SiC grating cavity acts as a perfect reflector; plasmon standing waves can be established under a certain size of the SiC grating. These standing waves can be confirmed using a Fabry–Perot model. The Fermi energy of graphene, and height of the grating can control the plasmon standing waves. Moreover, we analyze how the strong coupling between localized magnetic polaritons in the SiC grating and surface plasmons in graphene ribbons leads to the Rabi splitting of the absorption peak and perfect absorption in the mid-infrared region using a coupled harmonic oscillator model. These findings may promote the development of optoelectronic devices based on hybrid structures and can pave the way for the hybridization of the two types of modes.