Abstract
Optical activity is the rotation of the plane of linearly polarized light along the propagation direction as the light travels through optically active materials. In existing methods, the strength of the optical activity is determined by the chirality of the materials, which is difficult to control quantitatively. Here we numerically and experimentally investigated an alternative approach to realize and control the optical activity with non-chiral plasmonic metasurfaces. Through judicious design of the structural units of the metasurfaces, the right and left circular polarization components of the linearly polarized light have different phase retardations after transmitting through the metasurfaces, leading to large optical activity. Moreover, the strength of the optical activity can be easily and accurately tuned by directly adjusting the phase difference. The proposed approach based on non-chiral plasmonic metasurfaces exhibits large optical activity with a high controllable degree of freedom, which may provide more possibilities for applications in photonics.
Highlights
Optical activity is the rotation of the plane of linearly polarized (LP) light along the propagation direction as the light travels through optically active materials, and it has acquired considerable importance in analytical chemistry, spectroscopy, crystallography and molecular biology[1,2]
Theoretical analysis Any LP light can be written as an equal combination of right circularly polarized (RCP) and left circularly polarized (LCP) light[40]: ELP 1⁄4 ERCP þ eifELCP
The optical activity is the rotation of LP light by adjusting φ
Summary
Optical activity is the rotation of the plane of linearly polarized (LP) light along the propagation direction as the light travels through optically active materials, and it has acquired considerable importance in analytical chemistry, spectroscopy, crystallography and molecular biology[1,2]. When LP light is transmitted through optically active materials, the right and left circular polarization components of the LP light experience different refractive indexes, leading to a change in the relative phase between the two circular polarizations. The degree of rotation depends on the propagation length in the material and the specific rotation, which is proportional to the refractive index difference (Δn). For conventional optically active materials, Δn is related to the specific crystal system of the birefringent crystal. The strength of optical activity can be controlled by tuning the molecule arrangements of special optically active materials, such as liquid crystals and magneto-optical crystals
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