Graphene perfect absorber with loss adaptive Q-factor control function enabled by quasi-bound states in the continuum

Sangjun Lee,Sangin Kim,Joohyung Song

doi:10.1038/s41598-021-02318-8

Sangjun Lee, Sangin Kim + Show 1 more

Open Access

https://doi.org/10.1038/s41598-021-02318-8

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Journal: Scientific Reports	Publication Date: Nov 24, 2021
Citations: 9	License type: open-access

Affiliation: Ajou University

Abstract

Numerous device structures have been proposed for perfect absorption in monolayer graphene under single-sided illumination, all of which requires the critical coupling condition, i.e., the balance between the loss of graphene and the leakage rate of the device. However, due to the difficulty of the precise control of the quality of synthesized graphene and unwanted doping in graphene transferred to the substrate, the loss of graphene is rather unpredictable, so that the perfect absorption is quite difficult to achieve in practice. To solve this problem, we designed a novel perfect absorber structure with a loss adaptive leakage rate control function enabled by the quasi-bound states in the continuum (BIC) and numerically demonstrated its performance. Our designed device is based on a slab-waveguide grating supporting both the quasi-BIC and the guided-mode resonance (GMR); the quasi-BIC with an adjustable leakage rate controlled by an incident angle is responsible for absorption, while the GMR works as an internal mirror. Since the proposed device scheme can have an arbitrarily small leakage rate, it can be used to implement a perfect absorber for any kind of ultrathin absorbing media. Due to the simple structure avoiding an external reflector, the device is easy to fabricate.

Highlights

Numerous device structures have been proposed for perfect absorption in monolayer graphene under single-sided illumination, all of which requires the critical coupling condition, i.e., the balance between the loss of graphene and the leakage rate of the device
This is the fundamental problem of all the previously proposed perfect absorber schemes. To solve this problem, we newly propose a perfect absorber scheme with a controllable leakage rate based on a quasi-bound states in the continuum (BIC)
The quasi-BIC is adopted in the slab-waveguide grating (SWG) as the lossy resonant mode and its resonance should be tuned to the guided-mode resonance (GMR) and the background scattering which forms an internal reflector function

Summary

Introduction

Numerous device structures have been proposed for perfect absorption in monolayer graphene under single-sided illumination, all of which requires the critical coupling condition, i.e., the balance between the loss of graphene and the leakage rate of the device. Due to the difficulty of the precise control of the quality of synthesized graphene and unwanted doping in graphene transferred to the substrate, the loss of graphene is rather unpredictable, so that the perfect absorption is quite difficult to achieve in practice To solve this problem, we designed a novel perfect absorber structure with a loss adaptive leakage rate control function enabled by the quasi-bound states in the continuum (BIC) and numerically demonstrated its performance. Our group proposed another mirror-less perfect absorber scheme based on an asymmetric single resonator such as a slab-waveguide grating (SWG) by adopting a one-port mimicking concept[20] In this scheme, two indirectly coupled degenerate guided-mode resonance (GMR) modes are used to achieve a virtual one-port system, in which only one mode experiences loss and the other functions as an internal reflector in conjunction with the Fabry–Perot (F-P) like background scattering. The incidence angle dependence of quasi-BIC is analyzed by using the coupled mode theory (CMT)[5,6,38]

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Conclusion