Abstract
An independently tunable dual-resonance hybrid structure incorporating graphene is proposed to achieve selective light trapping and response tuning in the visible and near-infrared band. The incident light with different wavelengths are intensely localized in two separated resonant cavities via the synergetic effect of the guided mode resonances (GMRs) and optical Tamm states (OTSs), which leads to the strong enhancement of the light-matter interaction of graphene in different parts of the structure. The dual-band perfect absorption associated with critical coupling is achieved, whereas the two resonant modes can be independently tuned by adjusting the corresponding structural parameters. Furthermore, by dynamically changing the permittivity of the resonant cavities or the chemical potential of graphene, the absorption wavelength can be continuously adjusted and the absorption efficiency can be regulated stepwise.
Highlights
OVER the past decade, graphene has broadly attracted attention in the field of opto-electronics owing to its ultrahigh mobility and ultra-broad response band [1]
When light is incident from the top, the guided mode resonances (GMRs) and optical Tamm states (OTSs) excited by the top grating and the bottom distributed Bragg reflector (DBR) would localize the optical field in cavity1 and cavity2, forcing it to interact with the graphene inserted
Since the absorption properties of graphene is mainly related to the imaginary part of its permittivity (Imag(ɛg)), we further present Imag(ɛg) as a function of the chemical potential μc over a range from 0.7 to 1.3μm in Fig. 2(b), which clearly indicates that Im(ɛg) corresponding to different wavelengths decreases stepwise at certain μc values, leading to a direct weakening of the graphene light absorption
Summary
OVER the past decade, graphene has broadly attracted attention in the field of opto-electronics owing to its ultrahigh mobility and ultra-broad response band [1]. Dual or more channels may be desired in some applications, including multiband detectors [11], solar cells [12]and white light emitting devices [13]. For this case, some hybrid systems with multiple resonant modes have been proposed. Long[16] achieved multi-channel ultranarrow absorption by employing a subwavelength dielectric grating to excite multi-order guided-mode resonances. Most of these works conduct with the same monolayer of graphene as the active medium, without considering the independent extraction of dual-band signals. Designs that deposit graphene on the surface of the device may lead to damage to integrity and stability of the graphene layer during practical processing, resulting in additional loss channels[18]
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