Development of azobenzene material and research of its excited state enhanced three-order nonlinearity

The 3rd nonlinear optical susceptibility chi((3)) and its response time of the excited-state of 4'-(2 ", 4 ", 6 "-trichlorophenazoamino)-phenazo-4-nit robenzene were measured with the double-wave coupling technique of the YAG picosecond double (532nm) and triple (355nm) frequency laser. The measured chi((3)) increases by one order of magnitude. Its response time is also of an improvement. The study shows that the excited-state enhanced 3rd nonline ar optical susceptibility is directly proportional to the population in the related excited-state, and is saturated with the increase of the pumping l aser. The theory of the phase space filling of excitons was used to explain the experiment results. The exciton length of 22 X 10(-8) cm in the sample was thus obtained from the theory-fitted value, which agrees reasonably wi th the generally acceptable order of (20-50) X 10(-8) cm.