laser and gaussian beam propagation and transformationEncyclopaedia of Optical Engineering. Laser and Gaussian beam propagation and transformation. LASER AND GAUSSIAN BEAM PROPAGATION AND TRANSFORMATION In Encyclopaedia of Optical Engineering. R. Barry Johnson, Ronald G. Driggers, eds. Marcel Dekker, Inc. New York: 2002. Javier Alda Optics Department. Univesity Complutense of Madrid. School of Optics. Avda. Arcos de Jalón s/n. 28037 Madrid. Spain. Phone: +34.91.394.6874 Fax: +34.91.394.6885 E-mail: j.alda@fis.ucm.es October 2001 1. INTRODUCTION Optical engineers and researchers working in optics deal with laser beams and optical systems as usual tools in their specific areas. The knowledge of the special characteristics of the propagation of laser beams through optical systems has to be one of the keystone of their actual work, and the cle……