Multi-band spin-selective transmission and reflection in bi-layer T-shaped metamaterial

Abstract

The control of the spin angular momentum of light plays an irreplaceable role in modern photon applications. In this work, we proposed a chiral metamaterial based on a bi-layer T-shaped structure. When circularly polarized light is incident along the normal direction (-z), the spin-selective transmissions and reflections occur in the mid-infrared frequency, which results in different transmittance and reflectance in quad-band frequencies. Here, the difference in transmittance (ΔT) values are 0.5, 0.4, 0.5, and 0.7, respectively. And the difference in reflectance (ΔR) reaches up to 0.4, 0.3, 0.4, and 0.5, respectively. Due to the chirality of the structure, the resulting circular dichroism (CD) is close to 0.2. In addition, the frequency and amplitude of the quad-band spin selections can be easily manipulated by rotating the rotation angle θ. Finally, we found that the similar spin-selective transmission and reflection can be achieved in Gigahertz (GHz) and Terahertz (THz) wavebands. The metamaterial might promote the application and development of versatile photonic devices.