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Ultrasensitive optical absorption in graphene based on bound states in the continuum.

Zhang M, Zhang X - Sci Rep (2015)

Bottom Line: By taking suitable BICs, the selective absorption for S and P waves has not only been realized, but also all-angle absorption for the S and P waves at the same time has been demonstrated.We have also found that ultrasensitive strong absorptions can appear at any wavelength from mid-infrared to far-infrared band.These phenomena are very beneficial to biosensing, perfect filters and waveguides.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Beijing Normal University, Beijing 100875, China.

ABSTRACT
We have designed a sphere-graphene-slab structure so that the electromagnetic wave can be well confined in the graphene due to the formation of a bound state in a continuum (BIC) of radiation modes. Based on such a bound state, we have realized strong optical absorption in the monolayer graphene. Such a strong optical absorption exhibits many advantages. It is ultrasensitive to the wavelength because the Q factor of the absorption peak can be more than 2000. By taking suitable BICs, the selective absorption for S and P waves has not only been realized, but also all-angle absorption for the S and P waves at the same time has been demonstrated. We have also found that ultrasensitive strong absorptions can appear at any wavelength from mid-infrared to far-infrared band. These phenomena are very beneficial to biosensing, perfect filters and waveguides.

No MeSH data available.


(a) Schematic diagram of the sphere-graphene-slab structure. (b), (c) and (d) show the absorption as a function of wavelength λ under the normal incident wave. Here a is taken as 5.5185 μm. (b) Various thickness of the slab at r = 0.3a. (c) Various sizes of the sphere at D = 0.3a. (d) Different EF at r = 0.3a and D = 0.3a. The other parameters are identical with those in Fig. 1.
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f2: (a) Schematic diagram of the sphere-graphene-slab structure. (b), (c) and (d) show the absorption as a function of wavelength λ under the normal incident wave. Here a is taken as 5.5185 μm. (b) Various thickness of the slab at r = 0.3a. (c) Various sizes of the sphere at D = 0.3a. (d) Different EF at r = 0.3a and D = 0.3a. The other parameters are identical with those in Fig. 1.

Mentions: In the following, we study the absorption properties of monolayer graphene when it is put at the interface between the monolayer dielectric spheres and the dielectric slab as shown in Fig. 2(a). In order to study the absorption properties of monolayer graphene in such a structure, we have developed layer-multiple-scattering method to include the graphene layer. Details of our calculated method are provided in the Methods section. Based on such a method, we have calculated absorption (A) with different tunable variables of the system. The absorption is defined from the requirement of energy conservation A = 1-T-R. Here T and R represent the transmittance and reflectivity, which are defined as the ratio of the transmitted, respectively the reflected, energy flux to the energy flux associated with the incident wave. In our calculations, the lattice constant is taken as a = 5.5185 μm, the other parameters for spheres and the slab are taken identical with those in Fig. 1. At room temperature 300 K and for mid-infrared wavelengths, the conductivity of monolayer graphene may be approximated with a Drude-like expression3233343536where ω is the angular frequency, EF represents Fermi level of graphene and the electron relaxation time τ is taken to be 0.3 ps based on typical values of the carrier mobility37.


Ultrasensitive optical absorption in graphene based on bound states in the continuum.

Zhang M, Zhang X - Sci Rep (2015)

(a) Schematic diagram of the sphere-graphene-slab structure. (b), (c) and (d) show the absorption as a function of wavelength λ under the normal incident wave. Here a is taken as 5.5185 μm. (b) Various thickness of the slab at r = 0.3a. (c) Various sizes of the sphere at D = 0.3a. (d) Different EF at r = 0.3a and D = 0.3a. The other parameters are identical with those in Fig. 1.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4317701&req=5

f2: (a) Schematic diagram of the sphere-graphene-slab structure. (b), (c) and (d) show the absorption as a function of wavelength λ under the normal incident wave. Here a is taken as 5.5185 μm. (b) Various thickness of the slab at r = 0.3a. (c) Various sizes of the sphere at D = 0.3a. (d) Different EF at r = 0.3a and D = 0.3a. The other parameters are identical with those in Fig. 1.
Mentions: In the following, we study the absorption properties of monolayer graphene when it is put at the interface between the monolayer dielectric spheres and the dielectric slab as shown in Fig. 2(a). In order to study the absorption properties of monolayer graphene in such a structure, we have developed layer-multiple-scattering method to include the graphene layer. Details of our calculated method are provided in the Methods section. Based on such a method, we have calculated absorption (A) with different tunable variables of the system. The absorption is defined from the requirement of energy conservation A = 1-T-R. Here T and R represent the transmittance and reflectivity, which are defined as the ratio of the transmitted, respectively the reflected, energy flux to the energy flux associated with the incident wave. In our calculations, the lattice constant is taken as a = 5.5185 μm, the other parameters for spheres and the slab are taken identical with those in Fig. 1. At room temperature 300 K and for mid-infrared wavelengths, the conductivity of monolayer graphene may be approximated with a Drude-like expression3233343536where ω is the angular frequency, EF represents Fermi level of graphene and the electron relaxation time τ is taken to be 0.3 ps based on typical values of the carrier mobility37.

Bottom Line: By taking suitable BICs, the selective absorption for S and P waves has not only been realized, but also all-angle absorption for the S and P waves at the same time has been demonstrated.We have also found that ultrasensitive strong absorptions can appear at any wavelength from mid-infrared to far-infrared band.These phenomena are very beneficial to biosensing, perfect filters and waveguides.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Beijing Normal University, Beijing 100875, China.

ABSTRACT
We have designed a sphere-graphene-slab structure so that the electromagnetic wave can be well confined in the graphene due to the formation of a bound state in a continuum (BIC) of radiation modes. Based on such a bound state, we have realized strong optical absorption in the monolayer graphene. Such a strong optical absorption exhibits many advantages. It is ultrasensitive to the wavelength because the Q factor of the absorption peak can be more than 2000. By taking suitable BICs, the selective absorption for S and P waves has not only been realized, but also all-angle absorption for the S and P waves at the same time has been demonstrated. We have also found that ultrasensitive strong absorptions can appear at any wavelength from mid-infrared to far-infrared band. These phenomena are very beneficial to biosensing, perfect filters and waveguides.

No MeSH data available.