Physical origin of directional beaming emitted from a subwavelength slit

Abstract

We propose the physical origin for a directional beam of light emitting from a single subwavelength slit in metallic film that is characterized by a corrugation feature at the exiting side of the film. We theorize that the beaming phenomenon can be explained simply as surface plasmon diffraction along the corrugation as long as the multiple scattering effects are taken into account to restate the dispersion relationship of the surface plasmon. In order to prove our theory, both an experimental setup and numerical simulations were undertaken. Results obtained match well with our theory of an explanation based on a surface plasmon diffraction scheme.

Plasmonic beaming and active control over fluorescent emission

“…One period of this oscillation is comparable to the SPP wavelength (~380 nm) on the metal surface, which again confirms that the SPP propagation on the top metal surface has a key role in the beam formation 26 . The magnitude of g determines the phase that SPPs pick up in travelling from the central slit to the first groove.…”

Specialized directional beaming through a metalens and a typical application

“…One of the typical works is the presentation regard ing the control of beaming through the subwavelength metallic slits reported by Yu et al in Ref. [16][17][18]. In their discussion, they confirmed that convergence and diver gence of the beaming after the slits are determined by the relationship between the wave vector k SP and item of 2π/Λ, where Λ is the period of the corrugated structure on metal film, as shown in Figure 1A-C.…”

Small-divergence semiconductor lasers by plasmonic collimation

“…Thus the re-emitted light has a wavevector normal to the laser facet (u ¼ 0). At the same frequency, the wavevector of the SPs on a metal surface patterned with a grating (k sp -grating ) is larger than the wavevector of the SPs on a planar metal surface (k sp -planar ) 13 , which is almost equal to the free-space wavevector k o in the mid-infrared region of the spectrum. As a result, the grating period L (¼8.9 mm) should be smaller than the free-space wavelength (L ¼ 2p/k sp -grating , 2p/k sp -planar % 2p/k o ¼ l o ¼ 9.9 mm) in order to generate a collimated beam normal to the laser facet.…”

“…There have been subsequent theoretical and experimental studies of this aperture -groove structure [10][11][12][13][14] , but there have been very few attempts to integrate this structure into an active device [15][16][17] .…”