Study On Standing Wave Laser Chaos With Self Feedback

Chaos is a kind of irregular movement, which means that in a determinate nonlinear dynamic system, having no use for stochastic factor, a homoplastically stochastic in fact ordered movement is produced because of inner nonlinear interaction inside the system. It exists in various natural fields, so does it in laser.In some cases, chaotic laser is harmful, for example, our staff room is planning using an integral sphere to measure material reflectivity. In the experiment, the material reflected light may return to the oscillator cavity, which may result in laser chaos, and the measurement result will be inaccurate. In this case, optical isolation or making correction to the output light undulation by using the input light is not feasible.To solve the problem, we have to study the mechanism and condition of laser chaos, dig out the real facts and running order to avoid chaos according to the order.Based on semiclassical theory of laser, this paper was devoted to study a new mechanism of laser chaos resulted from laser self feedback in the standing wave condition. Serving for the theme that how the feedback coefficient and delayed time influence the laser chaos, some research were carried out as follow:The basic concepts of chaos concerned with the theme were reviewed. Based on the study of nonlinear dynamics of laser, the travelling wave equation and stability condition of Maxwell-Bloch equation were introduced. Then the production of chaos as well as its possible applications on national defence and civil economy was analyzed.Theory innovation: A single mode standing wave Maxwell-Bloch equation (include homogeneous and inhomogeneous conditions )was deduced on my own. The unitary Maxwell-Bloch equation of standing wave was also deduced. Then the stability of the unitary Maxwell-Bloch equation was analysed. The effect of feedback coefficient on the stability of the M-B equation was gained through a numerical simulation. As the feedback coefficient increased, the output laser changed from stability to chaos. The bigger the feedback coefficient, the more chaotic the output laser.Experiment innovation: a He-Ne laser chaos study was done in the experiment. With the change of the feedback intensity , the feedback length or the feedback angle, the chaotic rule of output laser was gained. The result showed that with the increase of the feedback intensity or the decrease of the feedback length , the laser chaos became more deeply. With the change of the feedback angle, a critical angle was discovered. When the feedback angle was bigger than the critical value, the output laser was stable; When the feedback angle was smaller than the critical value, the output laser was chaotic. The critical value decreased as the feedback length increased.This paper has applied importance in optical chaos application and in some case where optical isolation or making correction to the output light undulation by using the input light is not feasible.