Manipulating bandwidth of light absorption at critical coupling: An example of graphene integrated with dielectric photonic structure

Wang, Jie; Chen, Ang; Zhang, Yiwen; Jian-ping, Zeng; Zhang, Yafeng; Liu, Xiaohan; Shi, Lei; Zi, Jian

doi:10.1103/physrevb.100.075407

Cited by 55 publications

(31 citation statements)

References 31 publications

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“…Thus, η can be simply expressed as η = 1 − T , which is equivalent to the extinction. Here T and η can be calculated by the CMT, [ 36–41 ] which is phenomenological method to describe the interaction between a resonator and free‐space light. In the CMT, the dynamic equation for a single resonator coupled with two ports (see Figure a) can be written as

\frac{d a}{d t} = (- i ω_{0} - γ_{r} - γ_{a}) a + k S_{1 +}

where ω 0 is the resonant frequency of the resonant mode, γ r is the radiation coupling rate of the resonant mode and γ a is the intrinsic absorption rate, respectively.…”

Section: Design Principle For High‐efficiency Modulatormentioning

confidence: 99%

“…The CMT model is illustrated in Figure 1a. Due to energy conservation and reciprocal theorem, [ 40,41 ] k and γ r are related as

k = i \sqrt{γ_{r}}

. The transmittance is defined as

T = {(||, \frac{S_{2 -}}{S_{1 +}})}^{2}

where S 2− = S 1+ + ka is the transmitted light.…”

Section: Design Principle For High‐efficiency Modulatormentioning

confidence: 99%

“…It is clear that η reaches its maximum at resonant frequency ω 0 ,

η_{0} = 1 - \frac{1}{{(γ_{r} / γ_{a} + 1)}^{2}}

When γ r ≪ γ a , η 0 reaches its minimum, η 0 = 0. When γ r = γ a namely critical coupling, [ 40,41 ] η 0 is equal to 75%. When γ r ≫ γ a , η 0 is close to 100%.…”

Section: Design Principle For High‐efficiency Modulatormentioning

confidence: 99%

See 2 more Smart Citations

Transmission‐Type Optical Modulator Based on Graphene Plasmonic Resonator Integrated with Off‐Resonant Au Structure

Xia

Wang

Zhang

et al. 2020

Advanced Optical Materials

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In this paper, a transmission‐type graphene plasmonic modulator by introducing off‐resonant Au structure is theoretically and experimentally investigated. It is found that the modulation efficiency and bandwidth could be dramatically enhanced compared with bare graphene plasmonic structure. The validity of this proposed method is verified both in the 1D and 2D graphene plasmonic structures: ribbons and holes. This work will open up a new path to design the high‐efficiency modulators, switches, and multispectral detectors.

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\frac{d a}{d t} = (- i ω_{0} - γ_{r} - γ_{a}) a + k S_{1 +}

where ω 0 is the resonant frequency of the resonant mode, γ r is the radiation coupling rate of the resonant mode and γ a is the intrinsic absorption rate, respectively.…”

Section: Design Principle For High‐efficiency Modulatormentioning

confidence: 99%

“…The CMT model is illustrated in Figure 1a. Due to energy conservation and reciprocal theorem, [ 40,41 ] k and γ r are related as

k = i \sqrt{γ_{r}}

. The transmittance is defined as

T = {(||, \frac{S_{2 -}}{S_{1 +}})}^{2}

where S 2− = S 1+ + ka is the transmitted light.…”

Section: Design Principle For High‐efficiency Modulatormentioning

confidence: 99%

See 1 more Smart Citation

Transmission‐Type Optical Modulator Based on Graphene Plasmonic Resonator Integrated with Off‐Resonant Au Structure

Xia

Wang

Zhang

et al. 2020

Advanced Optical Materials

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“…The overall field profile, however, is not significantly altered by the SLG. The property of an absorbing material determines γ a ; however, γ a is not determined solely by material properties, but also by the interaction with the cavity structure 20 . Since the field distribution and its overlap with the absorbing material will decide the γ a for a Type B structure where an SLG is embedded inside the oxide layer, the DGL structure needs to be adjusted in order to achieve the near critical-coupling condition.…”

Section: Numerical and Theoretical Analysismentioning

confidence: 99%

“…As an alternative optical cavity, a guided resonance structure is used to meet the critical coupling condition, formed by a metasurface or 1D or 2D photonic crystal layer backed with a metallic or DBR [13][14][15][16][17][18][19] . The metasurface has a fixed thickness, but by manipulating the other parameters, such as grating period or the ratio of high to low refractive index regions within a unit cell, the decay rates of the resonance mode from the resonance structure can be tuned 13,20 . By manipulating these parameters and using a back mirror, the critical coupling condition can be met and thus total absorption is achieved 13,[21][22][23] .…”

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confidence: 99%

Dual-guiding-layer resonance structure with an embedded metasurface for quasi-critical coupling without a perfect mirror

Park

2020

Sci Rep

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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.

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Flexible Terahertz Metasurface Absorbers Empowered by Bound States in the Continuum

Xu,

Xue,

Fan

et al. 2024

Advanced Materials

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Terahertz absorbers are crucial to the cutting‐edge techniques in the next‐generation wireless communications, imaging, sensing, and radar stealth, as they fundamentally determine the performance of detectors and cloaking capabilities. It has long been a pressing task to find absorbers with customizable performance that can adapt to various environments with low cost and great flexibility. Here, perfect absorption empowered by bound states in the continuum (BICs) is demonstrated, allowing for the tailoring of absorption coefficient, bandwidth, and field of view. The one‐port absorbers are interpreted using temporal coupled‐mode theory highlighting the dominant role of BICs in the far‐field radiation properties. Through a thorough investigation of BICs from the perspective of lattice symmetry, the radiation features of three BIC modes are unraveled using both multipolar and topological analysis. The versatile radiation capabilities of BICs provide ample freedom to meet specific requirements of absorbers, including tunable bandwidth, stable performance in a large field of view, and multiband absorption using a thin and flexible film without extreme geometric demands. These findings offer a systematic approach to developing optoelectronic devices and demonstrate the significant potential of BICs for optical and photonic applications, which will stimulate further studies on terahertz photonics and metasurfaces.

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Manipulating bandwidth of light absorption at critical coupling: An example of graphene integrated with dielectric photonic structure

Cited by 55 publications

References 31 publications

Transmission‐Type Optical Modulator Based on Graphene Plasmonic Resonator Integrated with Off‐Resonant Au Structure

Transmission‐Type Optical Modulator Based on Graphene Plasmonic Resonator Integrated with Off‐Resonant Au Structure

Dual-guiding-layer resonance structure with an embedded metasurface for quasi-critical coupling without a perfect mirror

Flexible Terahertz Metasurface Absorbers Empowered by Bound States in the Continuum

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