ABSTRACT
Jacky Byatt In most laser applications it is necessary to focus, modify or shape the laser beam by using lenses and other optical elements. In general, laser-beam propagation can be approximated by assuming that the laser beam has an ideal Gaussian intensity profile, corresponding to the theoretical TEM00 mode. Coherent Gaussian beams have transformation properties that require special consideration. The output from single-mode (TEM00) lasers is highly Gaussian (helium-neon lasers and argon-ion lasers are very good examples). In contrast, high-power lasers often operate with many modes and are highly non-Gaussian. The propagation of non-Gaussian lasers is discussed later in this chapter.
