Abstract
In this article, the effects of the rotation angle between upper and lower n-fold rotational symmetric nano-structures are studied. Various modes of circular dichroism (single wavelength band, dual-wavelength bands, and more than two wavelength bands) in the wavelength band from 3.3 to 5 μm are realized. Circular dichroism up to 0.798 are observed. Meanwhile, sensitivity of circular dichroism to the rotation angle and reconfigure strategy for opposite responses has been discussed. Based on Born-Kuhn model, physical mechanism of mode’s switching is explained with charge distributions. The multi-mode chiroptical responses in mid-infrared band and the variety of design strategies have potential applications in the field of tunable multi-band chiral devices.
Highlights
Metamaterial is an artificial material with many electromagnetic properties that do not exist in nature, such as perfect absorption
When the rotation angle is set to 0° (i.e., Fig. 2(a)), significant asymmetric transmission can be observed in short wavelength band (3.3-3.95 μm), middle wavelength band (3.95-4.26 μm), and long wavelength band (4.26-5 μm)
When the rotation angle is set to 10° (Fig. 2(b)), a large asymmetric transmission can be observed in the middle and long wavelength bands
Summary
Metamaterial is an artificial material with many electromagnetic properties that do not exist in nature, such as perfect absorption Et al 2020), negative refraction (Valentine, et al 2008), electromagnetically induced transparency-like (Xu, et al 2019). It has provided excellent solutions for modulators, sensors, etc. When metamaterials have chiral properties, such as giant optical activity; circular dichroism; negative refractive index and etc. Chiral metamaterials have significant improvement in chiral parameters compared with natural chiral materials because of their strong electromagnetic coupling. As a typical phenomenon of chirality, circular dichroism (CD) is used to characterize the different electromagnetic responses of materials between left-hand circularly polarized (LCP) waves and right-handed polarized (RCP) waves. CD has been widely utilized in protein structure examining, nanostructural analyzing, medicine detecting, etc. (Berova, et al 2000; Ranjbar and Gill 2009)
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