Newsgroups: sci.physics.plasma
From: lawson@pax.llnl.gov (William S. Lawson)
Organization: Lawrence Livermore National Laboratory
Subject: Re: Short pulse group velocity Q

In article <2vu8rd$klt@mojo.eng.umd.edu>, mdp1@crux2.cit.cornell.edu (Mark)
writes:
|> I am working on research which includes an analytical calculation of the
|> group velocity of a short laser pulse in either vacuum or plasma. First,
|> a little clarification. This laser pulse is a Gaussian pulse both axially
|> and radially. When I say short pulse, I mean that the pulse length L <<
|> the Rayleigh length, but the wavelength lambda << L. I am trying to locate
|> any references or information regarding previous group velocity calculations
|> for such a pulse. If anybody knows where I might find a reference on this,
|> I would greatly appreciate your sending me information to the email address
|> listed below. The velocity in plasma is not even that important at this
|> point, for now I would just like a reference on short pulse propagation in
|> vacuum. I thank you in advance.

Short-pulse propagation in a vacuum is like any other kind of propagation in a
vacuum -- there is no distortion of any kind, and the group velocity is c. A
plasma is more complicated, but at optical frequencies, it shouldn't be too
bad. Any book on plasma theory should give you the dielectric tensor you need.
-- Bill Lawson