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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) Diagram of the sphere-slab structure and coordinate. The spheres are arranged in a square lattice with the lattice constant a. The radii of spheres are 0.3a. The slab is placed next to the spheres and the thickness is 0.3a. (b) shows the absolute value of the electric field in one primitive cell at . The incident wave is along Z-axis normally to the XY-plane, the amplitude of the incident field is 1 and the polarization is along X-axis. Red coordinate represents the field intensity distribution along the X-axis at the interface between the spheres and the slab (Y = 0, Z = 1.1); Blue coordinate corresponds to the field intensity distribution along the Z-axis at X = 0.01 and Y = 0.01. (c) and (e) describe the reflectivity R as a function of the reduced wavelength  and the component of wave vector kx for S and P wave, respectively. Because the resonant peaks are too sharp to be displayed, we highlight the bound states with dashed lines. The boundary between the black and colored region is the light line. The corresponding reflectivity for the S and P waves at various incident angles are given in (d) and (f) as a function of the reduced wavelength .
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f1: (a) Diagram of the sphere-slab structure and coordinate. The spheres are arranged in a square lattice with the lattice constant a. The radii of spheres are 0.3a. The slab is placed next to the spheres and the thickness is 0.3a. (b) shows the absolute value of the electric field in one primitive cell at . The incident wave is along Z-axis normally to the XY-plane, the amplitude of the incident field is 1 and the polarization is along X-axis. Red coordinate represents the field intensity distribution along the X-axis at the interface between the spheres and the slab (Y = 0, Z = 1.1); Blue coordinate corresponds to the field intensity distribution along the Z-axis at X = 0.01 and Y = 0.01. (c) and (e) describe the reflectivity R as a function of the reduced wavelength and the component of wave vector kx for S and P wave, respectively. Because the resonant peaks are too sharp to be displayed, we highlight the bound states with dashed lines. The boundary between the black and colored region is the light line. The corresponding reflectivity for the S and P waves at various incident angles are given in (d) and (f) as a function of the reduced wavelength .

Mentions: We consider a double layer structure consisting of monolayer dielectric spheres with a square lattice and a dielectric slab as shown in Fig. 1(a). The distance between two neighbor spheres is taken as a, the relative permittivity and relative permeability of spheres are marked by εs and μs, respectively. The relative permittivity and permeability of the dielectric slab are expressed by εd and μd. For nonmagnetic materials, μs = μd = 1. By choosing appropriate parameters of the structure, we construct a BIC at the interface between the monolayer dielectric spheres and the dielectric slab, and realize to trap EM waves at such a position. Then, we put a sheet of monolayer graphene at such a position and explore the interaction between external EM fields and the graphene.


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

Zhang M, Zhang X - Sci Rep (2015)

(a) Diagram of the sphere-slab structure and coordinate. The spheres are arranged in a square lattice with the lattice constant a. The radii of spheres are 0.3a. The slab is placed next to the spheres and the thickness is 0.3a. (b) shows the absolute value of the electric field in one primitive cell at . The incident wave is along Z-axis normally to the XY-plane, the amplitude of the incident field is 1 and the polarization is along X-axis. Red coordinate represents the field intensity distribution along the X-axis at the interface between the spheres and the slab (Y = 0, Z = 1.1); Blue coordinate corresponds to the field intensity distribution along the Z-axis at X = 0.01 and Y = 0.01. (c) and (e) describe the reflectivity R as a function of the reduced wavelength  and the component of wave vector kx for S and P wave, respectively. Because the resonant peaks are too sharp to be displayed, we highlight the bound states with dashed lines. The boundary between the black and colored region is the light line. The corresponding reflectivity for the S and P waves at various incident angles are given in (d) and (f) as a function of the reduced wavelength .
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1: (a) Diagram of the sphere-slab structure and coordinate. The spheres are arranged in a square lattice with the lattice constant a. The radii of spheres are 0.3a. The slab is placed next to the spheres and the thickness is 0.3a. (b) shows the absolute value of the electric field in one primitive cell at . The incident wave is along Z-axis normally to the XY-plane, the amplitude of the incident field is 1 and the polarization is along X-axis. Red coordinate represents the field intensity distribution along the X-axis at the interface between the spheres and the slab (Y = 0, Z = 1.1); Blue coordinate corresponds to the field intensity distribution along the Z-axis at X = 0.01 and Y = 0.01. (c) and (e) describe the reflectivity R as a function of the reduced wavelength and the component of wave vector kx for S and P wave, respectively. Because the resonant peaks are too sharp to be displayed, we highlight the bound states with dashed lines. The boundary between the black and colored region is the light line. The corresponding reflectivity for the S and P waves at various incident angles are given in (d) and (f) as a function of the reduced wavelength .
Mentions: We consider a double layer structure consisting of monolayer dielectric spheres with a square lattice and a dielectric slab as shown in Fig. 1(a). The distance between two neighbor spheres is taken as a, the relative permittivity and relative permeability of spheres are marked by εs and μs, respectively. The relative permittivity and permeability of the dielectric slab are expressed by εd and μd. For nonmagnetic materials, μs = μd = 1. By choosing appropriate parameters of the structure, we construct a BIC at the interface between the monolayer dielectric spheres and the dielectric slab, and realize to trap EM waves at such a position. Then, we put a sheet of monolayer graphene at such a position and explore the interaction between external EM fields and the graphene.

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.