constructing high-Q resonators with enhanced performances, which can be applied in various optical fields.22:T52d,Flexible control of light absorption within the lithography-free nanostructure is crucial for many polarization-dependent optical devices. Herein, we demonstrated that the lithography-free tunable absorber (LTA) can be realized by using two one-dimensional (1D) photonic crystals (PCs) consisting of an α-MoO₃ layer at visible region. The two 1D PCs have different bulk band properties, and the topological interface state-induced light absorption enhancement of α-MoO₃ can be realized as the α-MoO₃ thin film is inserted at the interface between the two 1D PCs. The resonant cavity model is proposed to evaluate the anisotropic absorption performances of the LTA, and the results are in good agreement with those of the transfer matrix method (TMM). The absorption efficiency of the LTA can be tailored by the number of the period of the two PCs, and the larger peak absorption is the direct consequence of the larger field enhancement factor (FEF) within the α-MoO₃ layer. In addition, near-perfect absorption can be achieved as the LTA is operated at the over-coupled resonance. By varying the polarization angle, the absorption channels can be selected and the reflection response can be effectively modulated due to the excellent in-plane anisotropy of α-MoO₃.23:T528,Bound states in the continuum (BICs) have drawn fundamental and technological interests due to their distinct features such as infinite quality factor and extremely localized fields. Recently, it has been shown that the light absorption of graphene can be effectively enhanced by using symmetry-protected quasi-BICs; however, the important role of the counterparts of accidental quasi-BICs for light absorption enhancement of ultrathin films has not been studied, to our knowledge. Herein, light absorption enhancement of graphene is demonstrated through the excitation of accidental quasi-BICs based on a simple silicon grating metasurface (SGM). Highly efficient light absorption of monolayer graphene can be achieved at over-coupled resonance, and the locations of the absorption peaks and their peak values can be dynamically tuned by varying the incident angle. The enhanced light absorption of graphene is originated mainly from the hybrid toroidal dipole and electric quadrupole mode according to the far-field multiple decompositions and near-field distributions of the unit cell of the structure. In addition, the absorption responses of the SGM with graphene are robust to the variation of structural parameters, and their optical performances can be highly modulated as the Fermi level of graphene is altered.

#	Concept	H-Index	Publications	Citations
1	Engineering	3	3	95
2	Applied Physics	3	3	95
3	Materials Science	2	2	43
4	Physics	2	2	72
5	Condensed Matter Physics	1	1	52

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