Ultra-broadband and completely modulated absorption enhancement of monolayer graphene in a near-infrared region

Bandwidth tunability of graphene absorption enhancement by hybridization of delocalized surface plasmon polaritons and localized magnetic plasmons

The bandwidth-tunable absorption enhancement of monolayer graphene is theoretically studied in the near-infrared wavelengths. The monolayer graphene is placed on the silver substrate surface with a periodic array of one-dimensional slits. Two absorption peaks are found to result from the hybridization of delocalized surface plasmon polaritons and localized magnetic plasmons. The positions of absorption peaks are accurately predicted by a coupling model of double oscillators. The full width at half maximum of absorption peaks is largely tuned from about 1-200 nm by changing the array period of slits. The effect of the slit size on absorption peaks is also investigated in detail. Our work is promising in applications for photoelectric devices.

Silicon-based asymmetric dimer-resonator grating for narrowband perfect absorption and sensing

In this work, a method for designing an ultra-narrowband absorber platform is presented with asymmetric silicon-based dimer-resonators grating. Within the infrared range of 3000 ∼ 4000 nm, two narrowband absorption peaks with absorptivity greater than 99% are produced by the absorber. Moreover, during the optical sensing, such an absorber platform shows high-performance sensitivity factors for the absorption wavelengths at λ₁ = 3468 nm (S = 3193 nm/RIU, FOM = 532) and at λ₂= 3562 nm (S = 3120 nm/RIU, FOM = 390). Strong scattering coupling and the magnetic resonances supported in this silicon based grating produce the high absorption. Otherwise, additional methods such as the polarization and incident angles are used to further tune the absorption responses in the intensity and wavelengths, indicating the feasibility for artificial manipulations. The achieved ultra-sharp perfect absorption and the related sensitive response hold the silicon based resonant scheme with wide applications in bio-sensing, spectral filtering and other fields.

Multiple dipolar resonant silicon-based metamaterials for high-performance optical switching and sensing

Dielectric nanostructures reinforcing light-matter interactions by manipulating geometric parameters have a sound momentum in optoelectronic applications. Here, we construct and numerically demonstrate a new platform with multiple dipolar resonant behaviors or impressive switching operation and optical sensing with a high sensitivity and figure of merit (FOM) via the graphene-silicon combined metamaterials. Ultra-sharp resonances are excited by introducing broken symmetry in such all-dielectric metamaterials (ADMs) consisting of two silicon trapezoidal bodies on a silica substrate. By analyzing the distributions of the electromagnetic fields and current densities, we find that two types of multipole modes have been excited to support multiple ultra-narrowband resonances in the near-infrared range. The influence of geometers, such as period, thickness, asymmetry parameters, and polarization angle of the incident light, has also been studied. In addition, by adjusting the Fermi levels of graphene, we realize a 95% amplitude modulation efficiency, which manifests perfect capacity for an optical switch. According to the calculated results, the highest sensitivity can reach 447.5 nm/RIU and a large FOM is also up to 1173 RIU^-1. This platform not only introduces new insight onto the achievement of high-quality ultra-sharp resonant responses but also offers a distinct possibility for the further development of high-quality related applications in optical sensors, notch filtering, strong light-matter interactions including the nonlinear optics, and multispectral optoelectronics.