Nonlinear output and critical behaviors of an optical multistable amplifier with conjugate polymer

This paper presents some results on the nonlinear output charactertistics and critical behaviors of a nonlinear optical system with conjugate polymer like polydiacetylenes, in a three-level model. Based on the model of interaction of this kind of matter with the pumping field, probing field and coherent field, the nonlinear susceptibility deduced by the method of the density matrix element, and the multistable output characteristics and effects of lasing or lasing wihtout inversion are furthe studied, using the dynamic equation of the 'forced oscillation model of laser and bistability'. On the other hand, through the approach of 'quasi-thermal dynamics', we analyzed the properites of the critical point of the system. The result shows that when the system is set on a tri-stable situation there exist an unstable critical point of second kind phase transiton and near which the behavior of the system had not been reported before, as we know.