Third-order nonlinear optical properties of undoped polyaniline solutions and films probed at 532 nm

The third-order nonlinear optical properties of polyaniline (PANI) solution s and films were investigated at 532 nm by use of Z-scan, power limiting, a nd optical Kerr gate techniques. The polymers studied were the undoped part ially oxidized (emeraldine base) and fully reduced (leucoemeraldine base) f orms of PANI. Our results demonstrate that the leucoemeraldine base is more suitable for use in devices such as all-optical switches and optical power limiters operating at 532 nm. The worse performance of the emeraldine base is due to the presence of defects inside the bandgap, of the polymer. (C) 2001 Optical Society of America.