Partial spatial coherence and polarization properties of surface plasmon fields

Abstract

We analyze theoretically the (spectral) spatial coherence and polarization properties in fluctuating surface plasmon fields generated at a lossy, thin metal film surrounded on both sides by air. Using rigorous electromagnetic interactions at the interfaces and the theory of optical coherence in 3D fields, we show that new coherence and polarization effects may occur in such plasmon fields. In particular, coherence lengths extending over several thousands of wavelengths, or coherence lengths significantly shorter than the wavelength of light in vacuum, can be found at certain frequencies. Using a recent 3D formulation, we also examine the degree of polarization in such random surface plasmon fields. We show that the field may be partially polarized in the immediate vicinity of the excitation of the surface plasmon modes, even though it is fully polarized farther away. In addition, we demonstrate that an increasing number of modes leads to a more polarized field above the plasmon excitation region, with the degree of polarization effectively independent of the height.