US developing untraceable weapons
schear at lvcm.com
Sat Oct 12 22:31:15 PDT 2002
At 10:17 PM 10/12/2002 -0400, Tyler Durden wrote:
>Well, there was also some other details left out by that article. A "100kW
>beam" doesn't tell you very much if you don't know the beam diameter.
It tells you the output power, from which one may estimate input power
>A 1310nm telecom laser can cause serious eye damage with 10mW, but that's
>10mW into, say 38 um^2. But it ain't going to do nothing to enemy aircraft
>located at a distance. A 100kW laser might easily have a smaller energy
>density depending on the diameter. In addition, there's the problem of
>focusing that thing through turbulence, but turbulence through certain
>wavelength windows may not be a problem.
Beam spread is one of the most significant considerations in delivering
high energy to distant targets. In general, one wants a large beam size to
The phenomenon of diffraction influences the propagation of Gaussian light
beams. The output of a laser is generally ''pencil-like'' in nature and has
a very low divergence, yet is subject to diffraction that causes it to
spread. Gaussian beam theory deals with this effect. The Rayleigh range, Z
sub R, is used as a criterion for determining the spreading of a
monochromatic Gaussian light beam as it propagates in free space.
In 1987 it was discovered that were ''nondiffracting'' beam types. The
zeroth-order Bessel beam is one such solution and results in a beam with a
narrow central region surrounded by a series of concentric rings. Ideally
this beam type exhibits no diffraction or spreading, in practice it is
possible to obtain Bessel beams of less than 1/10 the divergence of a
Gaussian beam of otherwise similar properties. Bessel beams have been the
subject of intense investigastion for a broad range of optical applications.
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