Double metal subwavelength slit arrays interference to measure the orbital angular momentum and the polarization of light.

We put forward a double-slit interference device based on two metal subwavelength slit arrays to measure the orbital angular momentum (OAM) and the polarization of beams simultaneously. The subwavelength slit serves as a localized spatial polarizer, and each slit array can be regarded as a wide diffraction-slit. When an OAM beam is normally incident upon the two slit arrays, the interference fringes twist, and the displacement depends on the topological charge of OAM beams. We present a detailed theoretical analysis of this measurement model. This model does not need additional reference light and is a linear model.