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 requirements.
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 reduce divergence. 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. http://www.st-and.ac.uk/~atomtrap/papers/AJPBessel.pdf http://www.st-and.ac.uk/~atomtrap/Research/IBB.htm