A team of scientists from the University of Stuttgart, the
Max-Planck-Institute of Solid State Research in Stuttgart, the University of
Pennsylvania and by Carl Zeiss AG Corporate Research has imaged wireless
transmission of optical power between two optical nanoantennas. The researchers
developed a novel method based on photoluminescence to sensitively probe
optical fields around nanostructures and applied their technique to image the
transmission of optical signals.The results appear in the latest issue of the
journal Nature Communications ("Imaging and steering an optical wireless
nanoantenna link"). The method developed by team is a very powerful tool
in understanding the propagation of light between optical nanostructures.
Optical nanoantennas
tailor the transmission and reception of optical signals. Owing to their
capacity to control the direction and angular distribution of optical radiation
over a broad spectral range, nanoantennas are promising components for optical
communication in nanocircuits. Here we measure wireless optical power transfer
between plasmonic nanoantennas in the far-field and demonstrate changeable
signal routing to different nanoscopic receivers via beamsteering. We image the
radiation pattern of single-optical nanoantennas using a photoluminescence
technique, which allows mapping of the unperturbed intensity distribution
around plasmonic structures. We quantify the distance dependence of the power
transmission between transmitter and receiver by deterministically positioning
nanoscopic fluorescent receivers around the transmitting nanoantenna. By
adjusting the wavefront of the optical field incident on the transmitter, we
achieve directional control of the transmitted radiation over a broad range of
29°. This enables wireless power transfer from one transmitter to different
receivers
When you use your cell phone to place
a call or to send a text message, your phone connects to a nearby transceiver
station via an antenna link. Information is transmitted efficiently and
wirelessly using this invisible cable connecting your hand-held device to the
wire network. It has been a dream to take the concept of antenna links from the
radio frequency regime to the optical domain. Combining the enormous bandwidth
of optical communication with the flexibility and low loss of antenna links
renders this a very exciting concept to transmit optical signals. An optical
nanoantenna link would allow extremely high bandwidth signal transmission
between nanoscale devices. This could be used for example to speed up
communications between integrated circuits. Optical nanoantenna links could
even be reconfigured by steering the transmitted beam in the same way as is done
in radar technology.The team led by Prof. Harald Giessen of the 4 th Physics
Institute at the University of Stuttgart fabricated optical nanoantenna
structures using electron beam lithography in collaboration with the
Max-Planck-Institute for Solid State Research. These nanometer scale metal
structures control optical fields in the same way as conventional radio
frequency antennas direct the transmission and reception of radio waves. The
scientists then positioned photoluminescent molecules around the nanostructures
with nanometer scale accuracy. This allowed them to image the distribution of
optical energy around the nanoantennas. The team applied their technique to
observe for the first time the transmission of optical energy between two
linked optical nanoantennas. They further quantified the power transmission
efficiency of the link and observed that the signal transmission has low loss,
turning optical nanoantenna links into a very promising approach for
transmission of optical signals.Having demonstrated the transmission of optical
power between two optical nanoantennas, the researchers implemented a device
capable of angular beam steering. This idea was inspired and supported by Dr.
Michael Totzeck from Carl Zeiss AG in Oberkochen. An array of transmitting
antennas was used, having slightly different phases of the signals transmitted
from the individual antennas. This results in the radiated optical beam
propagating in different directions depending on the phase of the transmitters
due to interference. The research team achieved this by shaping the wave front
of the field incident on the transmitting array. By controlling the wave front
the transmitted radiation could be steered over a large angular range of 29
degrees
Source: University of Stuttgart
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