We review the principle and methodology of leakage radiation microscopy (LRM) applied to surface plasmon polaritons (SPPs). Therefore we first analyse in detail the electromagnetic theory of leaky SPP waves. We show that LRM is a versatile optical far-field method allowing direct quantitative imaging and analysis of SPP propagation on thin metal films. We illustrate the LRM potentiality by analyzing the propagation of SPP waves interacting with several two dimensional plasmonic devices realized and studied in the recent years.PACS numbers:

We demonstrate that nanostructures carefully designed on both sides of a thin suspended metallic membrane couple light into a chiral near field and transmit vortex beams through a central aperture that connects the two sides of the membrane. We show how far-field orbital angular momentum (OAM) indices can be tailored through nanostructure designs. We reveal the crucial importance of OAM selection rules imposed by the central aperture and derive OAM summation rules in perfect agreement with experimental data. PACS numbers:Structured light beams with phase or polarization singularities, have revealed unique optical properties with applications ranging from super-resolution imaging [1] to high-resolution sensing [2] and from particle micromanipulation [3] to quantum optics [4]. Currently, chiral nanostructures draw promising routes for enhancing singular optical signatures, thus providing extended control over new functionalities in metamaterial science [5] and biomimetics engineering [6,7]. Interestingly, while the connection between optics and chirality is well established for 3 dimensional (3D) chiral structures, the interaction of chiral light with 2D chiral objects is a topic of on-going debate [8][9][10], with strong potential in physical chemistry for chirality enhancement in the near field [11][12][13].Recently, singular optical effects have been discussed in the near field, in particular in relation to chiral surface plasmon (SP) modes which have been shown to carry orbital angular momentum (OAM) [14][15][16][17]. But until now, singular SP modes and associated spin-orbit coupling have only been probed in the near field [18][19][20]. Studies on plasmonic beaming with OAM have been scarce [21,22] and the relation between near-field chirality and OAM in the far field was never addressed.In this Letter, we demonstrate that nanostructures carefully designed on both sides of a thin suspended membrane lead to tailoring optical OAM in the far field. Single and double-sided plasmonic structures consisting of concentric grooves periodically spaced from a central subwavelength aperture -so called plasmonic bull's eye (BE)-have shown extraordinary optical transmission and beaming effects [23,24]. Yet, the OAM behaviour of these structures was not discussed. This Letter presents a comprehensive analysis of the OAM transfer during plasmonic in-coupling and out-coupling by chiral nanostructures at each side of a membrane, stressing in particular the role of a back-side structure in generating vortex beams as e iℓϕ with tunable OAM indices ℓ. With such membranes, we achieve propagating beams carrying OAM up to |ℓ| = 8. Moreover we reveal and analyze the fundamental role of the central aperture in the system's OAM generation through specific selection rules.Our device consists of a suspended thin (h ∼ 300 nm) metallic membrane, fabricated by evaporating a metal film over a poly(vinyl formal) resine supported by a transmission electron microscopy copper grid. After evaporation, the resine is removed using a focused ion-bea...

We introduce a point-like scanning single-photon source that operates at room temperature and offers an exceptional photostability (no blinking, no bleaching). This is obtained by grafting in a controlled way a diamond nanocrystal (size around 20 nm) with single nitrogen-vacancy color-center occupancy at the apex of an optical probe. As an application, we image metallic nanostructures in the near-field, thereby achieving a near-field scanning single-photon microscopy working at room temperature on the long term. Our work may be of importance to various emerging fields of nanoscience where an accurate positioning of a quantum emitter is required such as for example quantum plasmonics.