Excitations of Multiple Fano Resonances Based on Permittivity-Asymmetric Dielectric Meta-Surfaces for Nano-Sensors

Abstract

We have designed an all-dielectric device based on permittivity-asymmetric rectangular blocks on meta-surfaces, yielding multiple Fano resonances with high sensitivity and high figure of merit (FOM) in the near-infrared regime. By introducing different materials to break the permittivity-symmetry, three sharp Fano peaks are generated with high Q-factors arising from the interference between the sub-radiant modes and the magnetic dipole resonance modes. Combining the field distributions and the multipole decomposition in Cartesian coordinates, the resonance modes are analyzed to be magnetic quadrupoles (MQs) and magnetic dipoles (MDs). Furthermore, the dependence on materials and geometric parameters has been studied. The maximal sensitivity, FOM and Q-factor reach 394nm/RIU, 4925 and 14437, respectively. This proposed structure provides a good alternative to geometry-asymmetric meta-surface structures and may be used for multichannel sensing, nonlinear optical devices, and laser.

Ultra-high Q-factor and amplitude-tunable Fano resonance in vanadium dioxide–silicon hybrid metamaterials

“…Correspondingly, the Qfactor is approximately 165 198 from the formula, Q = Re(u)/ 2Im(u) = u 0 /2g. 32 In this work, in-plane SLR could be generated in the metamaterial due to the periodic arrangement of the resonator units in the design. When the resonance frequency of a single resonator is close to the SLR frequency, a strong energy transfer can be achieved from the incident terahertz wave to the local plasma, resulting in a sharp plasma resonance.…”

Dual band symmetry-protected terahertz bound states in the continuum inside the spoof localized surface plasmon induced-transparency windows

“…One has to use a unified theory to explain both phenomena at the same time. Thus, we use the coupled oscillator model to explain our discovery [31,[43][44][45][46]. Herein, we employed a coupled five harmonic oscillators model to mimic the behavior of the PIT as well as BIC effect in terahertz transmittance spectra since there are three dark modes and two bright modes in total, as shown in figure 3.…”

“…In this coupled oscillator model, the bright mode is the intrinsic resonance considered as the continuum and the dark mode is the leaky mode as shown in figure 3(c). The interaction between bright and dark modes under incident terahertz wave E = E 0 e −iωt in a coupled system can be described by the following equations [31,[43][44][45][46]:…”

“…Therefore, the three coupled oscillators model is composed of two intrinsic modes (ν 1 , ν 2 ) and three dark modes (ν 3 , ν 4 , ν 5 ) shown in figure 3. By solving the equations ( 2)-( 6), the resonant amplitudes expression of the five modes can be written as [31,[43][44][45][46]:…”

Label-Free Bound-States-in-the-Continuum Biosensors

“…All-dielectric structures that support BICs have been widely used in the design of high- Q biosensors based on their advantages of low loss and high functionality. In this section, some all-dielectric BICs biosensors are introduced, including BICs gratings [ 57 , 58 , 59 , 60 , 61 , 62 , 63 ], symmetry-broken [ 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 ] and topological-boundary-states-governed [ 78 ] BICs metasurfaces, and BICs PhCSs [ 56 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 ].…”