Lasers as a Test Bench for Theories of Non-Equilibrium Structures

Abstract

The appearance of intensity pulsations at the output of a laser was noted immediately after the first successful operation of the ruby laser. At first this phenomenon was thought to be the consequence of external noise, optical inhomogeneities in the active medium or mechanical instabilities; later it became apparent that, while the stability of the output intensity was surely conditioned by instrumental imperfections, self-pulsing could also be the consequence of the nonlinear interaction between the electromagnetic radiation and the active atoms [1]. In 1975 H. Haken [2a] showed that the single mode equations of the laser are isomorphic to the Lorenz equations [2b]. Because the latter at that time were already known to include chaotic oscillations among its possible solutions, Haken’s proof endowed the laser with a complex temporal phenomenology of its own. In the early 1980’s the first experimental observations of period doubling, bifurcations and chaos began to appear in the literature [3 4]. Maybe, the main reason for the delay was the fact that during two decades laser physicists were worried more on the design of new and more stable lasers than in the study of laser physics. Since 1982 a a considerably body of evidence has been uncovered leading to the observation of period doubling, quasi-periodicity, intermittency, crises, Shil’nikov instabilities and many other phenomena in optical systems [5 6].