I. INTRODUCTION In recent years intensive investigations of surface plasmon polaritons (SPPs) have been made in the promising context of nanophotonics. This research is actually motivated by the current trends for optical device miniaturisation and by the possibilities of merging aspects of nanophotonics with those of electronics. SPPs are electromagnetic waves bounded to dielectric-metal interface. As surface waves, SPPs are exponentially damped in the directions perpendicular to the interface [1]. Furthermore, SPPs could be used to transfer optical information in a two dimensional (2D) environment. This appealing property can be used for optical addressing of different 2D optical systems and nanostructures located at a dielectric/metal interface. Actually several 2D SPP devices including passive nanostructures including mirrors or beam splitter and active elements like molecules or quantum dots are currently under development and investigation. Developments such as these raise the prospect of a new branch of photonics using SPPs, for which the term ”plasmonics” emerged [2–4]. However, for experimental investigations of optical devices an important characteristic of SPP modes is that their spatial extent is governed and defined by the geometry of the nanoelements rather that by the optical wavelength [7]. This consequently opens possibilities for breaking the diffraction limit but requires instruments of observation adapted essentially to the subwalength regime and being capable of imaging the propagation of SPPs in their 2D environment. Usually the analysis of the subwalength regime implies necessarily near field optical (NFO) methods [5, 6] able to collect the evanescent (i. e., non radiative) components of the electromagnetic fields associated with SPPs. However, when the metal film on which the 2D optical elements are built is thin enough (i. e ., with a thickness below 80-100 nm) and when the subtratum optical constant (usually glass) is higher than the one of the superstratum medium an other possibility for analyzing SPP propagation occurs. This possibility is based on the detection of coherent leaking of SPPs through the substratum. Such a far-field optical method is called leakage radiation microscopy (LRM) [8–10] and allows indeed a direct quantitative imaging and analysis of SPP propagation on thin metal films. The aim of this article is to present a short overview of recent progress in the field of SPP 2