Tunable Bound States in the Continuum in a Reconfigurable Terahertz Metamaterial

Abstract

Bound states in the continuum (BIC) is an exotic concept describing systems without radiative loss. BICs are widely investigated in optics due to numerous potential applications including lasing, sensing, and filtering, among others. This study introduces a structurally tunable BIC terahertz metamaterial fabricated using micromachining and experimentally characterized using terahertz time domain spectroscopy. Control of the bending angle of the metamaterial by thermal actuation modifies the capacitance enabling tuning from a quasi‐BIC state with a quality factor of 26 to the BIC state. The dynamic response from the quasi‐BIC state to the BIC state is achieved by blueshifting the resonant frequency of the LC mode while maintaining a constant resonant frequency for the dipole mode. Additional insight into the tunable electromagnetic response is obtained using temporal coupled mode theory (CMT). The results reveal the effectiveness of bi‐layer cantilever‐based structures to realize tunable BIC metamaterials with potential applications for nonlinear optics and light‐matter control at terahertz frequencies.

Full-Space Wavefront Shaping of Broadband Vortex Beam with Switchable Terahertz Metasurface Based on Vanadium Dioxide

“…In the numerical calculations, the basic size parameters of the unit cell are optimized by the CST and determined as follows: P = 26 µm; l 1 = 18 µm; l 2 = 15.17 µm; w = 2 µm; α = 45 • ; β = 22.5 • ; h 1 = 0.2 µm; h 2 = 10 µm; and h 3 = 2 µm. The gold film with a conductivity of 4.56 × 10 7 S/m is patterned to create the Z-shaped anisotropic metal structures [29], and the lossless polyimide with the permittivity of εPI = 3.5 is selected as the dielectric layer material [30].…”

Angular‐Dispersive Narrowband Absorption Induced by Quasi‐BIC in SiO2‐Au Metamaterial

“…Usually, quasi-BIC can be stimulated in geometry symmetry-broken, oblique incidence, or coupling-mode resonant system, respectively, named as symmetry-protected BIC [26,27] and accidental BIC, [28] and shows considerable sensitivity and tunability in both geometry parameter space and incident momentum space. [29][30][31] From the first experiment observation of quasi-BIC in photonic crystal (PhC) in 2013, [32] periodic micro-nano structures such as PhCs and metamaterials have been an ideal platform to deeply research and practically apply quasi-BIC owing to their highly artificial designability and complementary metal-oxide-semiconductor compatibility in wide spectra ranging from terahertz to visible spectra. [33] In 2018, Koshelev et al proposed a series of in-plane asymmetry resonator designs using high-refractive-index dielectrics or metals and demonstrated their quasi-BIC properties.…”