Abstract:A dual-band terahertz (THz) absorber using the periodic cross-shaped graphene arrays is presented. It is shown that the dual-band light absorption enhancement of graphene results from the edge graphene plasmon (EGP) resonance, and the locations of the two absorption peaks can be precisely estimated by using the Fabry-Pérot (F-P) cavity model. Slight residual reflection remains at the two absorption peaks because the input impedance of the cross-arm cannot be perfectly matched with the free space impedance. In … Show more
“…To corroborate the correlation between the absorption performances and the related electromagnetic parameters of the Cr-based metasurface, here we investigate the input impedances of the total structure by using the impedance theory. Based on the impedance theory [ 55 , 56 ], the impedance Z of the Cr-based MA can be obtained by the extraction of the scattering parameters as follows: where S 11 , S 22 , S 21 , S 12 are S parameters; k , n , and D are the wave vector, the effective refractive index, and thickness of the structure, respectively. The reflection of the Cr-based MA can be calculated as R = [( Z − Z 0 )/( Z + Z 0 )] 2 , where Z and Z 0 are the normalized impedance of the structure and free space, respectively.…”
Section: Physical Basis For Ultrabroadband Absorption Enhancementmentioning
confidence: 99%
“…To corroborate the correlation between the absorption performances and the related electromagnetic parameters of the Cr-based metasurface, here we investigate the input impedances of the total structure by using the impedance theory. Based on the impedance theory [55,56], the impedance Z of the Cr-based MA can be obtained by the extraction of the scattering parameters as follows:…”
Section: Physical Basis For Ultrabroadband Absorption Enhancementmentioning
Broadband metamaterial absorbers (MAs) are critical for applications of photonic and optoelectronic devices. Despite long-standing efforts on broadband MAs, it has been challenging to achieve ultrabroadband absorption with high absorptivity and omnidirectional characteristics within a comparatively simple and low-cost architecture. Here we design, fabricate, and characterize a novel compact Cr-based MA to achieve ultrabroadband absorption in the visible to near-infrared wavelength region. The Cr-based MA consists of Cr nanorods and Cr substrate sandwiched by three pairs of SiO2/Cr stacks. Both simulated and experimental results show that an average absorption over 93.7% can be achieved in the range of 400–1000 nm. Specifically, the ultrabroadband features result from the co-excitations of localized surface plasmon (LSP) and propagating surface plasmon (PSP) and their synergistic absorption effects, where absorption in the shorter and longer wavelengths are mainly contributed bythe LSP and PSP modes, respectively. The Cr-based MA is very robust to variations of the geometrical parameters, and angle-and polarization-insensitive absorption can be operated well over a large range of anglesunder both transverse magnetic(TM)- and transverse electric (TE)-polarized light illumination.
“…To corroborate the correlation between the absorption performances and the related electromagnetic parameters of the Cr-based metasurface, here we investigate the input impedances of the total structure by using the impedance theory. Based on the impedance theory [ 55 , 56 ], the impedance Z of the Cr-based MA can be obtained by the extraction of the scattering parameters as follows: where S 11 , S 22 , S 21 , S 12 are S parameters; k , n , and D are the wave vector, the effective refractive index, and thickness of the structure, respectively. The reflection of the Cr-based MA can be calculated as R = [( Z − Z 0 )/( Z + Z 0 )] 2 , where Z and Z 0 are the normalized impedance of the structure and free space, respectively.…”
Section: Physical Basis For Ultrabroadband Absorption Enhancementmentioning
confidence: 99%
“…To corroborate the correlation between the absorption performances and the related electromagnetic parameters of the Cr-based metasurface, here we investigate the input impedances of the total structure by using the impedance theory. Based on the impedance theory [55,56], the impedance Z of the Cr-based MA can be obtained by the extraction of the scattering parameters as follows:…”
Section: Physical Basis For Ultrabroadband Absorption Enhancementmentioning
Broadband metamaterial absorbers (MAs) are critical for applications of photonic and optoelectronic devices. Despite long-standing efforts on broadband MAs, it has been challenging to achieve ultrabroadband absorption with high absorptivity and omnidirectional characteristics within a comparatively simple and low-cost architecture. Here we design, fabricate, and characterize a novel compact Cr-based MA to achieve ultrabroadband absorption in the visible to near-infrared wavelength region. The Cr-based MA consists of Cr nanorods and Cr substrate sandwiched by three pairs of SiO2/Cr stacks. Both simulated and experimental results show that an average absorption over 93.7% can be achieved in the range of 400–1000 nm. Specifically, the ultrabroadband features result from the co-excitations of localized surface plasmon (LSP) and propagating surface plasmon (PSP) and their synergistic absorption effects, where absorption in the shorter and longer wavelengths are mainly contributed bythe LSP and PSP modes, respectively. The Cr-based MA is very robust to variations of the geometrical parameters, and angle-and polarization-insensitive absorption can be operated well over a large range of anglesunder both transverse magnetic(TM)- and transverse electric (TE)-polarized light illumination.
“…For a fixed wavelength, Re( n eff,y ) will be the maximum for the smallest w and the largest d . Here, the slit resonance can be equivalent to a localized F-P cavity resonance due to the standing wave patterns along the y direction, and the F-P cavity resonance condition can be described as 57,58 :where δ is the phase shift, λ is the resonance wavelength, l = 400 nm is the F-P cavity length, ϕ = π/2 is the phase shift, m is an integer which represents the resonant order, and m = 2 in calculation.Figure 3( a ) Real part of the effective refractive-index Re( n eff,y ) of the slit resonance mode of the SSPs vs. wavelength under different location d and width w of the slit. ( b ) Resonance wavelengths estimated by using the F-P cavity model for different location d and width w of the slit.…”
The effect of ultra-narrowband light absorption enhancement is presented by using metamaterials with symmetry-broken square silicon patches (SSPs). The symmetry of the SSP can be broken by introducing a narrow slit deviating from its center. By breaking the symmetry of the SSPs, slit resonance mode with standing wave patterns can be excited, and the locations of the absorption peaks can be well estimated by using the Fabry-Pérot (F-P) cavity model. Although there is no excitation of surface plasmon resonance, ultra-narrowband light absorption can be achieved by minimizing the reflectance through perfect impedance matching and simultaneously eliminating the transmittance by the metallic substrate. Good ultra-narrowband absorption features can be maintained as the parameters of the buffer layer and the SSPs are altered. When this type of symmetry-broken SSPs-based metamaterial is used in refractive-index sensors, it shows excellent sensing properties due to its stable ultra-narrowband absorption enhancement.
“…Plasmonic perfect absorbers (PPAs) based on surface plasmon polaritons (SPPs) effect serve a pivotal role in optical communication, filters, imaging, sensors. − PPAs have attracted considerable attention for their fascinating characteristics due to the enhancing and absorbing electromagnetic (EM) waves in metal nanoparticles (MNPs) and their capability of the realization of highly integrated optical circuits (IOCs). − The close relationship of the SPPs associated with the refractive index (RI) of the surrounding medium makes them become an available option for detecting the biomolecule, toxic liquid, and flammable gas. − The narrow-FWHM (full width at half-maximum) PPAs can be utilized to detect RI materials since its unique optical property is very sensitive to environmental change. ,− So far, many PPAs sensors have been proposed and achieved remarkable advances. ,− Some of the previously reported PPAs concern the wavelength in the terahertz (THz) . THz stands for the segment of the EM radiation between microwave and infrared ranging from 3 mm to 30 μm.…”
Optical absorbers
with multiple absorption channels are required
in integrated optical circuits and have always been a challenge in
visible and near-infrared (NIR) region. This paper proposes a perfect
plasmonic absorber (PPA) that consists of a closed loop and a linked
intersection in a unit cell for sensitive biosensing applications.
We elucidate the physical nature of finite element method simulations
through the absorptance spectrum, electric field intensity, magnetic
flux density, and surface charge distribution. The designed PPA achieves
triple channels, and the recorded dual-band absorptance reaches 99.64
and 99.00% nm, respectively. Besides, the sensitivity can get 1000.00
and 650 nm/RIU for mode 1 and mode 2, respectively. Our design has
a strong electric and magnetic field coupling arising from the mutual
inductance and the capacitive coupling in the proposed plasmonic system.
Therefore, the designed structure can serve as a promising option
for biosensors and other optical devices. Here, we illustrated two
examples, i.e., detecting cancerous cells and diabetes cells.
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