All-dielectric terahertz metasurfaces with high Q Fano resonance based on indirect perturbation and bound states in the continuum

Enhancing the Goos–Hänchen shift based on quasi-bound states in the continuum through material asymmetric dielectric compound gratings

“…The proposed asymmetric dielectric compound gratings in this paper can be fabricated using existing semiconductor fabrication technology. [19,21] First, a layer of silicon is deposited on the silica substrate by plasma-enhanced chemical vapor deposition (PECVD), and the required silicon grating is obtained through electron beam lithography (EBL) and reactive ion etching (RIE). Second, a dielectric layer with refractive index n is deposited via epitaxial technique, followed by EBL and RIE, and a grating with refractive index n can be obtained.…”

“…Two common methods to break the plane symmetry of a grating or metasurface are to change the geometry of the grating or metasurface unit [17][18][19] and to change the refractive index of the grating or metasurface unit material. [20][21][22][23] Most of the current studies are based on geometric asymmetry to achieve symmetry-protected QBIC resonance, but this approach suffers from the problem of imposing fundamental limitations on achieving the lowest geometric asymmetry, especially in the near-infrared and visible spectral bands.…”

“…[23] The Q factor is directly proportional to the negative quadratic of the asymmetry of the structure. [17][18][19] Therefore, the Q factor will significantly vary with the change in structural asymmetry, but there may be errors in the fabrication process, resulting in poor controllability. [19] Compared with geometric asymmetries, material asymmetry has the advantage of abundant means of implementation, such as by current injection, [24] photothermal effect, [25] Kerr effect [26] and epitaxy.…”

“…[17][18][19] Therefore, the Q factor will significantly vary with the change in structural asymmetry, but there may be errors in the fabrication process, resulting in poor controllability. [19] Compared with geometric asymmetries, material asymmetry has the advantage of abundant means of implementation, such as by current injection, [24] photothermal effect, [25] Kerr effect [26] and epitaxy. [22] In addition, the material asymmetric grating or metasurface has strong controllability.…”

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

“… 20 In the same year, Feng et al proposed a metamaterial, whose unit structure consisted of asymmetric triple-parallel silicon rectangles and recorded a high Q -factor and high robustness for it. 21 In 2023, Wang et al proposed a two-band metamaterial absorber at terahertz frequency with a periodically patterned metallic structure on the top of the wafer, which exhibited perfect absorption properties and a high Q -factor in two bands, 0.89 THz and 1.36 THz. 22 In 2023, He et al proposed a four-band tunable narrow-band terahertz absorber that had a perfect multimodal absorption in the 1–9 THz range and could sense with high sensitivity.…”