Enhanced absorption of graphene strips with a multilayer subwavelength grating structure

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The optical absorption of graphene strips covered on a multilayer subwavelength grating (MSG) surface is theoretically investigated. The absorption of graphene strips with MSG is enhanced in the wavelength range of 1500 nm to 1600 nm by critical coupling, which is associated with the combined effects of a guided resonance of MSG and its photonic band gap effect. The critical coupling of the graphene strips can be controlled by adjusting the incident angle without changing the structural parameters of MSG. The absorption of graphene strips can also be tuned by varying key parameters, such as grating period, strip width, and incident angle.