Tunable Negative Index Metamaterials Based On Topological Insulator

Topological insulator as a new material of quantum physics has attracted more and more attention. Bi2Se3 is a very potential topological insulator. By changing the intrinsic properties of Bi2Se3 dielectric layer, for the first time we effectively control the intrinsic resonance of metamaterials in the near-infrared spectrum and achieve broadband double negative refractive index. Traditional tunable metamaterials require the integration of layer structure and electrode for tuning the effective optical parameters. Compared with traditional tunable metamaterials, this paper designs tunable metamaterials with nanoscale small size and easy-integration and wide application. The present research investigates the implementation of near-infrared tunable metamaterials and the construction of model, then simulates the model theoretically and calculates numerically. We adopt a sandwich structure (metal/dielectric/metal) to achieve both strong magnetic resonance and strong electric resonance, in this way we reduce the energy loss.Previously, metamaterials require light in a particular angle of incidence to excite Surface Plasmon Resonance (SPR), which requires light to incident at specific angle. However, most of metamaterials are not active at near-infrared regime. Besides, near-infrared light plays an important role in biomedical detection. Elliptical nanohole array (ENA) metamaterials have more and more application for their excellent structural characteristics and simple fabrication. The normal incident light can activate SPR. Meanwhile, the modification of its geometry structure and size could make it work at near-infrared regime and have better optical properties. As a result, the tunable metamaterials working at near-infrared regime are introduced based on fishnet metamaterials.In this paper we introduce the topological insulator Bi2Se3 as dielectric layer, since its dielectric constants for different phases vary a lot, with physical method of tuning, the effective parameters of the structure shift in a wide range and we can achieve tunability and double negative index metamaterials in near-infrared region. Negative index metamaterials can be used in biosensor, super lens, invisible cloak, new energy sourcessuch as solar cell, etc. This study presents Finite-Difference Time-Domain (FDTD) method in detail and applies it to simulate electromagnetic field intensity distribution of metamaterials. Electromagnetic properties of metamaterials obtained from the simulation is helpful. Moreover, we also calculate the optical properties of metal/dielectric/metal trilayer metamaterials numerically and theoretically verify the broadband tunability of ENA metamaterials based on topological insulator. Additionally, we implement the extraordinary physical property of double negative index at near-infrared spectrum.