In this paper, a triple-band hybridization coherent perfect absorber based on graphene metamaterial is proposed, which consists of graphene concentric nanorings with different sizes and a metallic mirror separated by SiO₂ layer. Based on the finite-difference time-domain (FDTD) solution, triple-band coherent perfect absorption is achieved at frequencies from 0.6 THz to 1.8 THz, which results from the surface plasmon resonance hybridization. The wavelength of the absorption peak can be rapidly changed by varying the Fermi level of graphene. Most importantly, the wavelength of the absorption peak can be independently tuned by varying the Fermi level of the single graphene nanoring. Moreover, the triple hybridization perfect absorber is angle-insensitive because of the perfect symmetry structure of the graphene nanorings. Therefore, our results may widely inspire optoelectronic and micro-nano applications, such as cloaking, tunable sensor, etc.

The electromagnetic spectrum includes the frequency range (spectrum) of electromagnetic radiation and its corresponding wavelength and energy. Due to the unique properties of different frequency ranges of the electromagnetic spectrum, a series of functional devices working in each frequency rang have been proposed. Here, we propose a periodic subwavelength hoof-shaped structure array, which contains a variety of geometric configurations, including U-shaped and rectangle structures. The results show that the enhanced optical transmission (EOT) effect of the surface plasmon excited by the hoof-shaped structure is highly sensitive to the polarization of the incident light, which leads to the peak’s location shift and the amplitude intensity variety of transmission peaks of U-shaped structure in the case of coupling based on the surface plasmon of rectangle structure. In addition, take advantage of the EOT effect realized in the periodic hoof-shaped structure array, we propose a multifunctional plasmon optical device in the infrared range. By adjusting the polarization angle of the incident light, the functions of the optical splitter in the near-infrared range and the optical switch in the mid-infrared range are realized. Moreover, with the changes of the polarization angle, different proportions of optical intensities split are realized. The device has theoretically confirmed the feasibility of designing multifunctional integrated devices through a hoof-shaped-based metamaterial nanostructure, which provides a broad prospect for the extensive use of multiple physical mechanisms in the future to achieve numerous functions in simple nanostructures.

The optical response of a metamaterial can be engineered by manipulating the size, pattern, and composition of its cells. Here, we present a coloring device, which increases resolution while retaining adjustability. By adding different nanoparticles in the nanohole, the shift of the transmission peak in the visible regions is realizable and manageable, which means a series of different colors are revealed in this device. At the same time, it is also possible to fill the holes with dielectric materials of different refractive indices to achieve the purpose of color diversity. This method theoretically confirms the feasibility of designing a coloring device via surface plasmons-based metamaterial nanostructure, which holds great promise for future versatile utilization of multiple physical mechanisms to render multiple colors in a simple nanostructure.

The subwavelength structure based on metamaterial has been widely used in the application of structure color due to its unique characteristics. Here, a composite structure consisting of a circular hole and different number of metal strips is proposed. By changing the polarization direction of the incident light, the resonance peak in the visible light range shifts, and the material presents different colors. At the same time, take advantage of the shift of the resonance peak, a plasmonic optical switch, of which on/off states can be indicated by the structural color, is constructed, and the maximum contrast ratio is more than 20 dB. In addition, by means of changing the geometric parameters and materials of the metal strip, the colors presented basically cover the whole visible light range. This method theoretically proves the feasibility of using subwavelength structure to construct visual plasmonic optical switch using structural color in the visible light range, which provides a broad prospect for the application of multiple physical mechanism in nanostructure design.