We propose a convertible metamaterial device with triple-band and broad-band characteristics based on bulk Dirac semimetal (BDS) and vanadium dioxide (VO2). When VO2 is in the fully insulating state, the proposed convertible device presents three distinctive absorption peaks in terahertz (THz) range with absorptance >98%. Absorptance spectra analysis shows a clear independence on the conductivity of VO2 when the device act as a triple-band absorber. When VO2 is in the fully metallic state, the convertible device expresses a broad-band absorption. In addition, this broad-band absorptivity can be continuously adjusted by changing the conductivity of VO2. Importantly, without making any changes to the structure parameters, the system exhibits unique convertible mechanism from triple-band to broad-band absorption. Electric field distributions are further discussed to explore the physical origin of this convertible absorber. Benefitting from the variable Fermi level of BDS, resonance frequency can be dynamically tuned. This design approach combined the use of BDS and VO2 not only paves a new way to realize a convertible absorber from triple-band to broad-band absorption, but also enables us to control the resonance frequency and absorption intensity in THz range. It is believed that the tunable converter provides plentiful applications such as modulator, energy harvesting and optic-electro switches.
Coherent perfect absorption (CPA) is realized in metasurfaces composed of crossed vertical bulk Dirac semimetal (BDS) stripes and S i O 2 . Under the illumination of two counter-propagating coherent beams, the coherent absorption is continuously controlled from almost 0 (approximately 6.2 × 10 − 5 ) to 99.97% by changing the beams’ relative phase, which gives a modulation depth of about 1.6 × 10 4 . Furthermore, the coherent absorption can be controlled substantially by varying the relative intensity, the Fermi energy of BDS, and the structural parameters of the metasurfaces. Further research shows that the metasurface has broadband angular selectivity: CPA frequency splits into TE and TM polarization bands under oblique incidence. Our results provide an effective way to manipulate the interaction of light and BDS, and there may be potential applications in coherent detectors and optical modulators.
In this paper, influence of InP coupling cavity on Fano resonance of sub wavelength MIM waveguide was studied by FDTD. It was observed that the resonant wavelengths of mode mj (j = 1, 2, 3) were closely related with the height H2 of InP coupling cavity. In addition, before and after the addition of air cavity, the relative farfield intensities I was a function of height H2. Therefore, InP as discrete state could be used as the filling dielectrics of Fano resonance in the MIM waveguide.
In this paper, influence of InP coupling cavity (height H2) on Fano resonance of sub wavelength MIM waveguide was studied by FDTD. It was observed redshift of the resonance peaks of mode mj (j=1, 2, 3) with H2 increase and the resonant wavelengths of mode mj (j=1, 2, 3) were a function of the height H2. Before and after the addition of air cavity, the relative farfield intensities I was a function of height H2. Therefore, InP as discrete state would be used as the filling dielectrics of Fano resonance in the MIM waveguide.
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