Tunable Chiral Response Of Monolayer Black Phosphorus Metamaterials In Far-Infrared Band

Metamaterials have attracted increasing attention due to their performance and characteristics beyond those of natural materials.Chiral metamaterials are specially designed metamaterials,while often exhibit much stronger chirality effect than natural materials.By changing structural parameters and using tunable materials,chiral metamaterials are easier to regulate chirality properties than natural materials.Two-dimensional materials have attracted the attention of researchers due to their ultra-thin and tunable characteristics.Monolayer black phosphorus is a tunable two-dimensional material and has anisotropic characteristics.Therefore,monolayer black phosphorus will play an important role in the fields of chirality and polarization control.The dissertation designs metamaterials working in the far infrared band based on monolayer black phosphorus,and studies the extrinsic chirality,intrinsic chirality and tunable characteristics.The main work includes:1.A metamaterial based on square monolayer black phosphorus units is designed.The metamaterial exhibits circular dichroism effect and circular birefringence effect on obliquely incident circularly polarized light,and also exhibits weaker circular conversion dichroism effect.Its circular dichroism effect exists in two adjacent bands with amplitudes of 14.0%and-18.7%.Its circular birefringence effect has a strong peak with an amplitude of 16.4°.The effects of various structural parameters,the inclination angle of incident light and the electron concentration on the chirality properties of the metamaterial were studied.In particular,the electron concentration of monolayer black phosphorus can effectively tune the chirality properties of the metamaterial.When the electron concentration is2?10^{1 3}cm^-2,the metamaterial exhibits a weaker chirality effect.When the electron concentration is9?10^{1 3}cm^-2,the circular dichroism of the metamaterial reaches 23.0%and the circular birefringence reaches 21.3°.2.A metamaterial based on cascade structures of square monolayer black phosphorus units is designed.The metamaterial has intrinsic chirality properties,and it exhibits circular dichroism effect and circular birefringence effect on vertically incident circular polarized light.Its circular dichroism effect exists in two adjacent bands,with amplitudes of-12.2%and17.5%.Its circular birefringence effect has a strong peak with an amplitude of-18.1°.The effects of various structural parameters,the inclination angle of incident light and the electron concentration on the chirality properties of the metamaterial were studied.The electron concentration of monolayer black phosphorus has a significant tuning effect on the chirality properties of the metamaterial.When the electron concentration is1?10^{1 3}cm^-2,the metamaterial exhibits a weaker chirality effect.When the electron concentration is9?10^{1 3}cm^-2,the circular dichroism of the metamaterial reaches 29.4%and the circular birefringence reaches 87.2°.