Lattice induced transparency-like in symmetric metasurfaces tuned with incident angles in mid-infrared region

Abstract

It is very meaningful to implement a tunable transparency window device with a simple metasurface structure in the mid-infrared band. In this paper, we propose a symmetric metasurface structure that consists of thin layers of graphene and a split anti-ring (SAR). This structure can achieve a tunable lattice-induced transparency-like (LIT-like) spectral response in the wide frequency range of 20–40 THz. Our simulation results show that the realization of the LIT-like phenomenon is due to the strong coupling between the lattice diffraction resonance mode (LDRM) and the wide plasmon resonance mode produced by SAR. The LIT-like response can be dynamically shifted by adjusting the incident pitch angle, the single and double LIT-like can also be switched by adjusting the azimuth angle, which provides convenient post-fabrication tunability. The coupling mechanism of the single LIT-like phenomenon is explained via a dual-oscillator model, which agrees well with the simulation results. In addition, the effects of spacer layer thickness, spacer layer refractive index, ambient refractive index on the position and size of the transparency window are analyzed. Lastly, a tunable delay bandwidth product between 0.46 and 0.86 will be produced due to the addition of graphene. Our finding manifests a novel design of the mid-infrared dynamically tuned slow-light device. • The symmetric metasurface can realized the LIT-like effect, which is produced by the strong coupling of plasmonic mode and LDRM. • The LIT-like effect can be tuned in mid-infrared regime by changing the incident pitch angle. • Single and double transparency windows can be switched when the incident azimuth angle is 0° and 90°. • The delay bandwidth product can be dynamically controlled by Fermi energy and incident pitch angle.