Classical field theory methods in laser physics. III. Propagation of laser radiation in vacuum outside a resonator

The third Part of our work continues the analysis of the problem considered in Parts I and II J. Russ. Laser Res.,17, 205 (1996);18, 2 (1997)]. We continue the search for the answer to the question: What is laser radiation from the viewpoint of the classical theory of wave fields? Here, we give one of the possible interpretations of propagation of laser radiation in vacuum outside a resonator from both the nonrelativistic and relativistic points of view. The relation between the metric and the radiation field structure is noted. Moreover, the third Part contains the conclusion concerning the work as a whole. It presents the main observations that may be useful for further studies of the problem.