A novel polymer film doped with natural active chloroplastin was formed by spin coating backings. The nonlinear refractive index of this composite polymer was measured by picosecond laser pulses. Comparing our experimental setup for measuring nonlinear refractive index and the response time of our samples with the original Z-scan system proposed by M. Sheik-Bahae et al., we added a variable time delay path and a tunable probe beam into this system to implement the measurement of the response time and spectra of n2. The nonlinear refractive index and response time of the polymer film ((alpha) equals 1.29 cm-1) is about 4.9 X 10-8 esu and 85 ps. When we put a F-P filled with the polymer film into a nanosecond pulse laser path, we observed optical bistability phenomena. The rising time was less than 1 ns and the recover time was about 2.5 ns. Analyzing and comparing the nonlinearities of chloroplastin derived from heat effects and (pi) -electron transition, we found that the heat effects, reorientation, and redistribution of the chloroplastin molecule can be neglected and the large optical nonlinearities of the film were of electronic origin.
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