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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.
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Tunable Toroidal Response in a Reconfigurable Terahertz Metamaterial
Abstract Compared with the traditional electric and magnetic multipoles, the existence of a dynamic toroidal moment has received increasing interest in recent years. This is due to its novel electromagnetic response, including dynamic non‐radiating charge‐current configurations and non‐reciprocal interactions. Reconfigurable terahertz metamaterials where artificial toroidal metamolecules and traditional microelectromechanical systems bi‐material cantilever structures are integrated within the same unit cell are presented. Through modification of the bending angle by thermal actuation, the toroidal dipole intensity increases by five orders of magnitude in the out‐of‐plane direction with an overall increase in the toroidal intensity of nearly an order of magnitude. Terahertz time‐domain spectroscopy is used to determine the evolution of the transmission as a function of the bending angle. This enables numerical confirmation of the toroidal response using multipole decomposition with additional confirmation provided by phase analysis. The results demonstrate the use of bi‐material cantilevers to realize a tunable toroidal moment with potential applications in sensing and next‐generation communication technologies.
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- Award ID(s):
- 1810252
- PAR ID:
- 10362215
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Optical Materials
- Volume:
- 9
- Issue:
- 22
- ISSN:
- 2195-1071
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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