The invention relates to a quaii-BIC chiral metasurface device based on
refractive index modulation and a preparation method and application thereof.The chiral metasurface device comprises a plurality of sub-
wavelength structure partitions which are sequentially arranged along the X axis, and every two adjacent sub-
wavelength structure partitions are rotationally and symmetrically arranged relative to the Y axis; a sub-
wavelength structure in the sub-wavelength structure partition comprises at least two optical
dielectric layers which are stacked along the Z axis, at least one sub-wavelength structure in the sub-wavelength structure partition is obliquely arranged relative to the Y axis, and a
refractive index difference exists between the at least two optical
dielectric layers, so that the metasurface device realizes intrinsic
chirality. The metasurface device realizes tunable strong intrinsic
chirality at multiple wavelengths, and the preparation method has the advantages that the
processing difficulty is low, the thickness of the optical
dielectric layer is low, the thickness and the inclination angle of the optical
dielectric layer do not need to be accurately controlled, the lift-off process is compatible, and high-precision large-area metasurface device preparation can be realized.