ANALYSIS OF DISPERSIVE AND ABSORPTIVE BISTABILITY IN A 4-LEVEL SYSTEMTYPICAL OF ORGANIC MEDIA

We investigate a general theory of optical bistability fbr a four-leve l system with single and triple states. Both absorptive and dispersive mechanisms are included. By solving the stable-state equation of a de nsity matrix and using the mean-field approximation, we derive the sta te equation of bistability. The bistabilities with dispersion and abso rption of single and triplet states, including pure dispersion and pur e absorption, are numerically studied. The effects of cooperative para meters, resonant transition detuning, and cavity detuning parameters o n bistable behavior are analyzed. We find that the absorption of tripl et states is beneficial to dispersive bistability but is detrimental t o absorptive bistability. The detuning of the resonant transition betw een single states is detrimental to bistability, whereas that between triplet states is beneficial to bistability. The structure of four lev els with single and triplet states is a typicality of organic media. O ur analysis is helpful for research into bistability devices of organi c media. (C) 1997 Optical Society of America.