Angle-independent beam splitter based on spoof surface plasmon

In this work, we propose an angle-independent beam splitter based on spoof surface plasmon. Arbitrary incident waves can be divided in half, and scatter towards two specific and independent directions. The proposed beam splitter consists of the upper periodic metal cylinder and the metal grating below. The former is placed to modulate the incident wave and the spoof surface plasmon with the specified wave vector, and the latter is used to support the excited spoof surface plasmon. To verify the proposed functionalities, we design three beam splitters with different splitter angles and calculate their field distributions under the illumination of the same Gaussian beam. The ideal numerical results agree well with the theory.