[MURG] Joseph M. Graham Jr.

[Joseph M. Graham Jr.]

Hello, murg,

Physicists have made a new type of ultra-precise laser pointer by
"squeezing" a beam in two directions. Hans Bachor and colleagues at
the Australian National University in Canberra and the Université
Pierre et Marie Curie in Paris are able to position the beam with a
precision of 1.6 Angstroms. This is almost 1.5 times better than the
theoretical limit for a conventional laser. The technique could be
used to improve the performance of a range of optical instruments and
also in imaging applications in physics and biology (N Treps et al.
2003 Science 301 940).

Laser beams suffer from quantum noise and until recently researchers
believed that this noise would set a fundamental limit on the
resolution of devices. However, it is possible to overcome these
limitations by squeezing the fluctuations (that is, reducing the
uncertainty) in one of the variables describing the beam, at the
expense of increasing the fluctuations in another variable. 

Bachor and colleagues mixed a standard laser beam with two squeezed
light beams. They found that the fluctuation amplitude of the laser
beam decreased from 2.3 Angstroms - the standard quantum noise limit -
to 1.6 Angstroms. The researchers managed to order the photons in the
squeezed beams in two different transverse directions at the same
time. This cancels out the quantum noise in a particular measurement
position. 

"Such an effect had been predicted but has never been seen until now,"
team member Nicolas Treps told PhysicsWeb. "What finally made this
work possible was the merging of the beams in an optical cavity and
the ability to operate the two sources of squeezed light
simultaneously." 

The team now hopes to exploit the technique in atomic force
microscopy, measurements of refractive index and studies of molecules
in living cells. However, Treps and co-workers say that the technique
still requires more fundamental work and that real applications will
follow only after researchers have developed easy-to-use, efficient
sources of squeezed light


[From PhysicsWeb]

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Physicists have created "slow" and "fast" light in a crystal at room
temperature for the first time. The team at the University of
Rochester in the US used an 'alexandrite' crystal to reduce the speed
of light to just 91 metres per second, and also to make a laser pulse
travel faster than the speed of light. Previously these effects -
which are not in conflict with special relativity - had only been
observed at cryogenic temperatures or in complicated experimental
set-ups. The new technique could be used for applications such as
optical data storage, optical memories and quantum information devices
(M Bigelow et al. 2003 Science 301 200).

Light travels at a speed of 300 million metres per second in a vacuum,
but in recent years physicists have managed to slow laser pulses down
to speeds of metres per second - or to bring them to a complete halt -
in ultracold gases. In similar experiments physicists have observed
superluminal or faster-than-light pulse propagation. These effects
have also been observed in crystals at cryogenic temperatures and in
"hot" gases. Now Matthew Bigelow, Nick Lepeshkin and Robert Boyd have
observed the same effects in a much simpler system - a crystal at room
temperature. 

All the experiments exploit changes in the refractive index of an
optical medium caused by quantum interference effects. Whereas
previous experiments relied on a process known as "electromagnetically
induced transparency", the Rochester team exploited "coherent
population oscillations" in the crystal. This involves shining two
lasers - a pump beam and a weaker probe beam - at the crystal. Under
certain conditions the probe beam experiences reduced absorption over
a narrow range of wavelengths. The refractive index also increases
rapidly in this "spectral hole", which leads to a much reduced group
velocity - the velocity at which a laser pulse travels - for the probe
beam. 

Earlier this year, the Rochester team used this technique to reduce
the group velocity of a laser pulse to 58 metres per second in a ruby
crystal at room temperature. Bigelow and co-workers have now repeated
this feat in a crystal of alexandrite. Moreover, by using different
wavelengths they can make a spectral "antihole" in which the
absorption is higher, and which leads to superluminal propagation.
They observed light speeds of 91 metres per second for a laser with a
wavelength of 488 nanometres, and minus 800 metres per second for
wavelengths of 476 nanometres. Negative speeds indicate superluminal
velocities because the pulses appear to leave the crystal before they
enter it under these conditions. 

"Our technique is applicable to many solid materials, not just
alexandrite," Lepeshkin told PhysicsWeb. "Another important feature of
our approach is the ability to cover a fairly broad range of optical
frequencies." The researchers will now investigate solid state
materials with higher bandwidth to use in their system that are
suitable for communication applications.

Author
Belle Dumé is Science Writer at PhysicsWeb
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 Name:			Joseph M Graham Jr.
Apt.26D
Address: 		1701 Ocean Ave.
 Asbury Park, NJ 07712
United States
 Day Phone:		(732) 775-0265
 Evening Phone(732) 775-0265
 Email Address:		jmgj2 at netzero.com
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We don't need to understand the brain in order to replace it as a whole copy into the holographhic computer.
And after the Brain is in the holographhic computer we can cut the connectivity to the hippocampus.
And find a fact of time or event that happen in the past memory. No more lies with a hippocampus.


P.S. What did Bill Clinton do in the House.  (he he he)


Best regards. 

Joseph M. Graham Jr.
jmgj2 at netzero.com
2003-09-23