[MURG] (no subject)

[Joseph M. Graham Jr.]

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

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