Common-path surface plasmon interferometer with radial polarization

We present a common-path surface plasmon interferometer with radial polarization. We show how the V z effect, the output of the microscope versus defocus z, can be derived utilizing a radially polarized illumination and a virtual annulus. The measurement of the V z effect gives a strong signature of the surface plasmon propagation, which is functionally related to the material properties. We discuss the advantages of using radial polarization compared to linear polarization.