[extropy-chat] nanoantenna

[scerir]

[from 'Physics News Update']

LASER OPTICAL ANTENNAS represent a relatively new approach to
getting around the old diffraction limit characterizing conventional
optics, namely the inability of a lens to focus light for imaging
purposes to any better than about half the wavelength of the light
being used.  Like a rooftop antenna which grabs meter-sized radio
waves and turns them (courtesy of a tuned circuit) into signals far
smaller in physical extent, so the optical antenna converts visible
light into an illuminating beam of much higher resolving power.  For
example, 800-nm light can produce images with a spatial resolution
of no better than about 400 nm.  A new device, built by the groups
of Ken Crozier and Federico Capasso at Harvard, producing spot sizes
as small as 40 nm using 800-nm light, is the first optical antenna
to be fully integrated (laser and focusing apparatus on one
platform) and the first to prove (by directly measuring light
intensities) the narrowness of the focused spot of light.  Their
method combines two proven techniques---plasmonics, in which light
waves, striking a metal surface, can create plasmons, which are a
sort of electromagnetic disturbance (see
http://www.aip.org/pnu/2006/split/770-1.html for background) with a
wavelength less than that of the incoming light; and near-field
microscopy, in which the diffraction limit is avoided by placing the
specimen very close to the imaging device.  In the Harvard setup the
antenna consists of two gold patches (130 nm long by 50 nm wide)
separated by a 30 nm gap.  Light falling on the gold strips (which
sit right on the facet of an ordinary commercial laser diode)
excites a huge electric field in the gap.  A specimen located
beneath this gap sees it as a 30-nm wide burst of light (although at
this stage in the work the spot size is more like a 40 nm x 100 nm
rectangle).  In many forms of subtle microscopy, power is sometimes
feeble, but here, in pulsed operation, the antenna can generate a
robust peak intensity of more than a gigawatt/cm^2.  (For comparison
images recorded with a force microscope, an electron microscope, and
the new laser antenna, see http://www.aip.org/png/2006/266.htm ).
Crozier  (kcrozier at deas.harvard.edu, 617-496-1441) says that spot
sizes of 20 nm should be possible and that likely applications for
their laser antenna will be found in the areas of optical data
storage (where 3 terabytes of data could be stored on a CD),
spatially-resolved chemical imaging, and near-field scanning optical
microscopy (NSOM).  (Cubukcu et al., Applied Physics Letters, August
28, 2006; lab website at www.deas.harvard.edu/crozier ; see also
http://www.aip.org/pnu/2004/split/701-1.html)

[and something for extropic artists, maybe...] 

LARGE-AREA SENSOR SKINS AND MICROPHONES might be possible with
flexible transistors made from cheap ferroelectret packing foam.
Just as in ferromagnetic materials tiny magnetic dipoles become
permanently oriented in the presence of an applied magnetic field,
so in ferroelectric materials electric dipoles become permanently
polarized by the application of an electric field.   Ferroelectrets,
a novel class of cheap electroactive materials based on cheap
polymer foams, are often used as packing material and for thermal
insulation.  But now physicists at the Johannes Kepler University
(in Linz, Austria) and Princeton University (US) have shown that
ferroelectret films can muster electric fields big enough to trigger
(switch) a field effect transistor.  Hence many of the things
transistors are good for can be engineered using flexible, cheap
ferroelectret materials as building blocks.  Already the researchers
have demonstrated in the lab working versions of flexible
touch-sensors and microphones.  Ingrid Graz (ingrid.graz at jku.at)
says that her new form of soft electronics could be useful for
producing flexible paper-thin keyboards and flexible microphones for
mobile phones, active noise control devices, toys, hearing aids, and
surround-sound systems.  (Graz et al., Applied Physics Letters, 14
August 2006)