  High-contrast refractive indexes are pivotal in dielectric metasurfaces for
inducing various exotic phenomena, such as the bound state in the continuum
(BIC) and electric mirror (EM). However, the limitations of high-index
materials are adverse to the practical applications, thus low-contrast
metasurfaces with comparable performance are highly desired. Here we present a
low-contrast dielectric metasurface comprising radially anisotropic cylinders,
which are SiO2 cylinders doped with a small amount of WS2. The cylinder
exhibits unidirectional forward superscattering originating from the
overlapping of the electric and magnetic dipole resonances. When normal
illumination by a near-infrared plane wave, the metasurface consisting of the
superscattering constituents manifests a polarization-insensitive EM.
Conversely, when subjected to an in-plane incoming wave, the metasurface
generates a symmetry-protected BIC characterized by an ultrahigh Q factor and
nearly negligible out-of-plane energy radiation. Our work highlights the doping
approach as an efficient strategy for designing low-contrast functional
metasurfaces and sheds new light on the potential applications in photonic
integrated circuits and on-chip optical communication.
