A He-Ne laser is an example of a class A laser, which can be described by a single nonlinear
differential equation of the complex electric field. This laser system has only one degree of
freedom and is thus inherently stable. A He-Ne laser can be driven to the chaotic condition when a
large fraction of the output beam is injected back to the laser. In practice, this can be done
simply by adding an external mirror. In this situation, the laser system has infinite degrees of
freedom and therefore it can have a chaotic attractor. We show the fundamental laser equations and
perform elementary stability analysis. In experiments, the laser intensity variations are measured
by a simple photodiode circuit. The laser output intensity time series is studied using nonlinear
analysis tools which can be found freely on the internet. The results show that the laser system
with feedback has an attractor of a reasonably high dimension and that the maximal Lyapunov exponent
is positive, which is…