All-dielectric metasurfaces for intensity-controllable beam splitting and polarization conversion

Beam splitters and polarization converters of electromagnetic waves based on metasurfaces have been extensively studied. However, there are few reports on the ability to arbitrarily control the intensity ratio between different diffraction orders while achieving beam splitting and polarization conversion. In this paper, we propose a method to achieve polarization conversion and beam splitting with varying intensities by manipulating the superposition of the output orthogonal circularly polarized (OCP) light. Specifically, polarized light with certain intensities and phase distributions in multiple channels can be decomposed into the superposition of OCP light with varying amplitudes and phases. Under the excitation of circularly polarized (CP) light, the amplitudes and phases of the output OCP light can be manipulated by adjusting the size and rotation angle of the nanopillar within the meta-atom. We show three metasurfaces capable of converting CP light into OCP and linearly polarized light in dual channels, with the ability to vary the intensity ratios of these polarized lights. Simulations demonstrate that the diffraction efficiencies of the desired diffraction orders of three metasurfaces exceed 90%. This method provides a novel concept for the design of multifunctional meta-devices.