Nuts & Volts

■ BY JEFF ECKERT
ADVANCED TECHNOLOGY
NEW COHERENT LIGHT
SOURCE DISCOVERED
■ Emission of coherent light at 22 THz
from a molecular dynamics simulation
of shocked NaCl (table salt).
For 50 years or so, the only way to
generate coherent light has been
through the use of a standard or
free-electron laser, but researchers
from Lawrence Livermore National
Laboratory (www.llnl.gov) and the
Massachusetts Institute of Technology
(www.mit.edu) have discovered that
common table salt is capable of emitting
light in the range of 1 to 100 THz
when subjected to a mechanical shock.
Through a series of theoretical
calculations and experimental
simulations, scientists generated a
mechanical shock wave inside a
dielectric crystalline material, in this
case NaCl. One would expect to see
only incoherent photons and sparks
emitted from the shocked crystal, but
weak yet measurable coherent light
emerged. The emission frequencies
are determined by the shock speed
and the lattice makeup of the crystal.
In the illustration, the left panel
shows the emission of the light as a
function of time while the shock is
propagating. The right panel shows
the generated radiation as a function
8 March 2006
TECH KNOWLEDGEY
EVENTS, ADVANCES, AND NEWS
of location within the shocked crystal,
indicating that the 22 THz coherent
signal is generated at the
shock front (between the
white dotted lines).
According to Evan Reed,
a postdoctoral fellow at
LLNL, applications for
this research are
numerous, but the most
immediate result may be
a new diagnostic tool to
determine the properties
of shock waves.
Coherent light, being
very narrow bandwidth
radiation, is useful for
interferometry (the
measurement of two or more waves
coming together at the same time and
place, such as optical and shock
waves). Further experiments will be
conducted in collaboration with
researchers from the Los Alamos
National Laboratory (www.lanl.gov).
PHOTO COURTESY OF LAWRENCE LIVERMORE NATIONAL LABORATORY.
GALEX MAPS OUT THE
CARTWHEEL GALAXY
For nearly three years, the Galaxy
Evolution Explorer (GALAX)
PHOTO COURTESY OF NASA/JPL-CALTECH.
2006
space telescope has been in orbit,
observing galaxies in ultraviolet light
in an endeavor to gather 10 billion
years of cosmic history. A recent
subject of scrutiny is the Cartwheel
galaxy, which is of particular interest
because, about 100 million years
ago, a smaller galaxy plunged
through it, creating ripples of star
formation.
This is shown in the false-color
composite depiction, which is made
up of images from the GALAX
far-ultraviolet detector (blue), the
Hubble Space Telescope’s wide field
and planetary camera 2 in B-band
visible light (green), the Spitzer Space
Telescope’s infrared array camera at 8
microns (red), and the Chandra X-ray
Observatory’s advanced CCD imaging
spectrometer-S array instrument
(purple).
Although astronomers have not
identified exactly which galaxy collided
with the Cartwheel, two of three
candidate galaxies can be seen in this
image to the bottom left of the ring —
one as a neon blob and the other as a
green spiral. For more information
about the project and other images,
visit www.galex.caltech.edu
WAVEGUIDE
CONTROLS
SPEED OF LIGHT
Late last year, IBM
( w w w . i b m . c o m )
announced the creation
of a tiny device that was
described as a major
advancement toward the
eventual use of light
instead of electricity in
■ The GALEX orbiting
space telescope
contributed to this
composite image of
the Cartwheel galaxy.