Abstract

Recently, we presented an optical bistable system that consists of a laser diode interferometer with an optoelectronic feedback circuit. We analyzed the nonlinear property of the system and predicted that the unstable light output of the laser diode exhibits chaotic behavior provided an appropriate time lag is introduced in the feedback loop. In the present paper, we report the experimental observation of tangent bifurcation in the light output. We show that the laser output turns out to be a stable period three-cycle in a certain range of the bias injection current. This stable period three-cycle, however, will become unstable and evolves into its higher-even-order harmonic solutions with the increase of the delay time. Up to eighth-order harmonic solutions are experimentally observed. A reasonable interpretation of the phenomenon is given by considering the continuity model for the actual system. At the nearby parameter value of the tangent bifurcation, we also observed an unstable light output. Such instability may be considered as a type of intermittent chaos.

© 1991 Optical Society of America