Here we have investigated the strong coupling of the guided modes with different orders in graphene-based onedimensional (1D) dielectric grating structures in the visible wavelengths. We found that the guided mode resonances (GMR) with different orders can strongly couple with each other under the oblique incidence of light. Absorption spectral response exhibits a distinct spectral anti-crossing with the Rabi splitting up to 59.8 meV. Simulation results further show that the strong coupling of GMR modes enables the bound state in the continuum (BIC) in this coupled system, which can be flexibly modulated by adjusting structural parameters. The proposed hybrid grating structures will benefit the applications in on-chip optical filtering, sensing, and optoelectronic detection.
Here we propose a metasurface consisting of asymmetric dielectric tetramer arrays, which can realize a polarization-sensitive light modulation through toroidal dipole resonance (TDR) in the near-infrared (NIR) region. We found, by breaking the C4v symmetry of the tetramer arrays, two narrow-band TDRs can be created with the linewidth around 1.5 nm. Multipolar decomposition of scattering power and electromagnetic field distribution calculations confirm the excitation of TDRs. Our simulation results show that 100% modulation depth in light absorption and selective field confinement can be achieved by changing the polarization orientation of the incident light. Our findings will prompt versatile applications in optical switching, storage, polarization detection, and light emitting devices.
We have theoretically studied the strong coupling of the surface plasmon polaritons (SPP) and magnetic polaritons (MP) modes in an Au grating/dielectric/Au resonance structure in the near-infrared waveband. Our results show that SPP and MP modes can strongly interact with each other at the metal grating/dielectric/metal (MDM) interface, leading to a large Rabi splitting. We also find that the light absorptivity in the high- and low-frequency branches within the anticrossing region are abnormally different. Moreover, the simulation results indicate that strong SPP-MP coupling can be tuned by modulating the geometric parameters of the structure. The unique characteristics of strong coupling of SPP and MP modes in this simple MDM hybrid structure will be helpful in the design of various polaritonic devices.
Strong and controllable circular dichroism (CD) is of great significance in enormous applications of life science. Here we have theoretically investigated the CD response in an Au split-ring resonator (SRR)/graphene nano-ribbon arrays on a metal substrate. The circular dichroism (CD) intensity in the proposed structure can approach 50%. Our theoretical investigation indicate that the strong CD is arisen from the symmetry breaking with the longitudinal plasmonic coupling in this hybrid system. More interestingly, we find that the strong optical CD can be very robust to the change of geometrical parameters of SRR and graphene nanoribbon as well as their vertical separation. Our design provides a new route for developing the compact and robust optical chiral devices in application of biochemical sensing and optical communication.
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