Time：2014-03-27ClickTimes：
Antennas, which can implement conversion between free space electricmagnetic
field and guided waves, have been widely used for more than a century. In
optical frequency regime, optical antennas are served as a tool to control light
at nanoscale.
In order to control the coupling between light and surface plasmon polaritons
(SPPs), Jiasen Zhang’s group has investigated the resonant properties of optical
slot nanoantennas. Dr. Jing Yang et al. proposed asymmetric optical slot
nanoantenna pairs (AOLNPs) to implement broadband SPP directional coupling. Two
slot antennas with different size were fabricated in a gold film, which have
different resonant frequencies. For an incident wave, the phase retardation
between the antennas is generated, which results in directional coupling between
light and SPPs. They implemented unidirectional SPP launching using AOLNPs and
the extinction ratio is larger than 40. The AOLNPs were also used to control the
radiation direction of SPPs. A novel all-optical display device was presented to
show the propagation directions of SPPs using AOSNPs without any electric
device. This paper was published on Nano Letters [Yang et al., Nano Letters 14,
704-709 (2014)].
They also proposed L-shaped optical slot nanoantennas to obtain broadband
spin-controlled SPP launching and radiation. The phase retardation and spectra
overlapping between two resonant plasmon modes in the L-shaped optical slot
nanoantenna lie at the origin of this effect. SPP launching in two perpendicular
directions are controlled by the spin of the incident light. Broadband
directional launching of SPPs is achieved and the extinction ratio keeps larger
than 7dB within a wavelength range of 150 nm. Furthermore, the photon spin of
SPP radiation via the L-shaped optical slot nanoantennas is controlled by SPP
propagation directions. These investigations provide a route for spin-controlled
nanophotonic applications. This paper will published on Laser & Photonics
Reviews （http://onlinelibrary.wiley.com/journal/10.1002/%28ISSN%291863-8899）.
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Fig. 1. SEM image of the designed plasmonic display device using
optical slot nanoantenna array and the CCD images of the plasmonic
display device when the surface plasmon polaritons (SPPs) propagated
along four different directions. The white arrows on the top right
corner of the CCD images show the SPP propagation directions. From Nano
Letters 14, 704-709 (2014).
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Fig. 2 Directional SPP launching using L-shaped optical slot
nanotantennas. (a) SEM image of the experimental sample. (b) SEM image
of the L-shaped optical slot nanoantenna array. (c) and (d) are CCD
images of the scattering gratings for the left-circularly polarized and
right-circularly polarized incident light, respectively. From Laser &
Photonics Reviews (in press).
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