Tunable ultra-wideband graphene-based filter with a staggered structure.

We present a tunable ultra-wideband band-stop filter utilizing graphene with a straightforward staggered structure. The transmission spectrum has been meticulously analyzed using the effective-index-based transfer matrix method (EIB-TMM). The results demonstrate that the filtering properties can be precisely tailored by manipulating the Fermi energy level of graphene. Importantly, we have successfully achieved a remarkable ultra-wideband stopband by optimizing the staggered parameters. Our exploration of redefining the staggered structure through adjustments to three critical parameters has revealed a crucial role in expanding bandwidth. This investigation deepens our understanding of how nonperiodic structures can effectively broaden bandwidth and holds great promise for the prospective design of ultra-wideband band-stop devices.

Designing a nearly perfect infrared absorber in monolayer black phosphorus.

Black phosphorus (BP) is a type of 2D layered material with a direct bandgap that displays high carrier mobility and strong in-plane anisotropy; it also exhibits potential as a promising optoelectronic material for IR applications. In this paper, we propose a nearly perfect IR absorber composed of a metal film, a spacer with a monolayer BP inside, and a distributed Bragg reflector (DBR). The electric field is confined inside the resonator generated by the metal film and DBR, and the absorption can be enhanced up to nearly 100%, owing to the strong interaction of BP with the confined field. Our results show that the absorption performance of the proposed structure is not only critically dependent on the electron density but also relies on the position of the BP within the spacer. This dependence can be mitigated because the absorption peak wavelength can be tuned by adjusting the angle of the light and the parameters of the DBR. Moreover, the absorber can be served as a reflective linear polarizer based on the anisotropic absorption properties. Our work can be helpful in designing a narrow perfect absorber and polarization-sensitive devices for IR waves.

Design of an ultrasensitive SPR biosensor based on a graphene-MoS2 hybrid structure with a MgF2 prism.

We propose, to the best of our knowledge, a new configuration of a biosensor based on the graphene-MoS2 hybrid structure by adopting the lower refractive index MgF2 prism in order to improve the sensitivity and the figure of merit (FOM). We can obtain an ultrasensitive sensor with values of sensitivity and FOM as high as 540.8°/RIU and 145/RIU, respectively, by modulating the parameters in the configuration and comparatively choosing a different absentee layer material. The proposed structure is applicable in the realization of an integrated device for the surface plasmon resonance biosensor.