The GLMT-framework previously introduced concerns arbitrary shaped beams. In practice however, one is often concerned with well defined special kinds of beams and, when the nature of the beam is known, much more can be said about GLMT. In this chapter, we discuss the special case of Gaussian beams, with a complement providing more information on Gaussian beams and discussing other beams as well. Gaussian beams (laser beams in their fundamental mode TEM 00) are widely employed in the field of optical particle sizing, corresponding to our original motivation in developing the GLMT (, , ,  for gaining a fairly complete background). Examples of applications of GLMT to the technique of phase-Doppler for simultaneous measurements of sizes and velocities of particles in flows may be found in , , , , among others. Another kind of special beams which is becoming more and more important for optical particle sizing is laser sheets also called cylindrical waves (see for instance , , , , ). It is of interest to remark that the description of a Gaussian beam is a limit case of the description of a cylindrical wave. See also discussions of top-hat beams in , . Laser sheets and top-hat beams will be more extensively discussed in the complement. For phase-Doppler techniques, see chapter VIII.
KeywordsGaussian Beam Laser Sheet Beam Shape Bessel Beam Paraxial Approximation
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