Abstract
We propose an all-dielectric quasi-one-port resonance structure that achieves near perfect absorption without the use of a back mirror. The structure mainly consists of a high-refractive-index silicon metasurface and surrounding high-refractive-index guiding layers. The dual-guiding-layer (DGL) structure has high background reflectance and is designed to have a ratio of two decay rates into the upper and lower regions within a wider range. When an absorbing material is introduced into a DGL system, it can be designed to achieve a near critical-coupling condition by reducing the constraints in the two decay rates. By using single-layer graphene as an absorbing material, the DGL resonance structure shows an absorption of ~ 97% and a phase change of ∼ 0.95π near the wavelength of 1550 nm, confirming quasi-critical coupling. The optimized DGL structure is relatively insensitive to potential fabrication imperfections, and consequently, the expected average peak wavelength and absorption are obtained as 1549.29 nm and 96.74%, respectively. Angle-dependent absorption confirms that maximum absorption occurs under normal incidence. The DGL absorber is also designed to cover the whole C-band region, in order to meet the quasi-critical-coupling condition. All mode profiles are similarly quasi-symmetric along the metasurface due to the same DGL resonance mechanism.
Highlights
We propose an all-dielectric quasi-one-port resonance structure that achieves near perfect absorption without the use of a back mirror
For the rigorous-coupled wave analysis (RCWA) simulation, the graphene thickness is set as 0.335 nm and the complex refractive is estimated based on the equation of nSLG = 3.0 + j(5.446/3 μm−1)λ, where λ is the w avelength[33]
The duty cycle ranges from 0.3 to 0.6, which is converted to a grating bar width (DC·Λ) range of 238 to 476 nm
Summary
We propose an all-dielectric quasi-one-port resonance structure that achieves near perfect absorption without the use of a back mirror. We propose and analyze a dual-guiding-layer (DGL) resonance structure on an SOI platform without using a back mirror, that achieves near-perfect absorption using single-layer graphene (SLG). The maximum absorption of the DGL absorber using a graphene layer can be slightly less than 100% due to the intrinsic property of the two-port resonance structure, which does not use a back reflector.
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