17 research outputs found
In the diffraction shadow: Norton waves versus surface plasmon-polaritons in the optical region
Surface electromagnetic modes supported by metal surfaces have a great
potential for uses in miniaturised detectors and optical circuits. For many
applications these modes are excited locally. In the optical regime, Surface
Plasmon Polaritons (SPPs) have been thought to dominate the fields at the
surface, beyond a transition region comprising 3-4 wavelengths from the source.
In this work we demonstrate that at sufficiently long distances SPPs are not
the main contribution to the field. Instead, for all metals, a different type
of wave prevails, which we term Norton waves for their reminiscence to those
found in the radio-wave regime at the surface of the Earth. Our results show
that Norton Waves are stronger at the surface than SPPs at distances larger
than 6-9 SPP's absorption lengths, the precise value depending on wavelength
and metal. Moreover, Norton waves decay more slowly than SPPs in the direction
normal to the surface.Comment: 8 pages, 8 figure
Enhanced optical transmission through arrays of subwavelength apertures in noble and transition metals
Arrays of subwavelength holes in metal film show enhanced
transmission when compared to what is expected from classical
diffraction. It appears that this phenomenon is crucially related to
surface plasmon polaritons. By their nature, surface plasmon
polaritons are particularly sensitive to the optical properties of
the metal film. In this work we relate in the optical regime these
properties on the enhanced transmission
Compact Antenna for Efficient and Unidirectional Launching and Decoupling of Surface Plasmons
Controlling the launching efficiencies and the directionality of surface plasmon polaritons (SPPs) and their decoupling to freely propagating light is a major goal for the development of plasmonic devices and systems. Here, we report on the design and experimental observation of a highly efficient unidirectional surface plasmon launcher composed of eleven subwavelength grooves, each with a distinct depth and width. Our observations show that, under normal illumination by a focused Gaussian beam, unidirectional SPP launching with an efficiency of at least 52% is achieved experimentally with a compact device of total length smaller than 8 μm. Reciprocally, we report that the same device can efficiently convert SPPs into a highly directive light beam emanating perpendicularly to the sample