Central metal ion enhances the excited state optical nonlinearity of naphthalocyanine compound

The third-order optical nonlinearities of lead and palladium naphthalocyanine compounds were studied comparatively using Z-scan technique with ns laser pulses at 532 nm. The experimental results showed that the two kinds of naphthalocyanine compounds also indicated strong nonlinear absorption (reserve saturable absorption) and nonlinear refraction(self-focusing) characteristics. Nonlinear absorption coefficient for lead and palladium naphthalocyanine compounds by theroetical fitting were 6.5410-10 m/W and 3.9010-10 m/W, reprectively. Nonlinear refractive index coefficient n2 were 1.6810-10 esu and 8.0410-11 esu, reprectively. The second-order molecular hyperpolarizabilities were 3.4410-28 esu and 2.5710-28 esu, reprectively, which were approximately about 105 order in magnitude than that of CS2(4.3210-33 esu). The experimental results show that the lead naphthalocyanine compound exhibits great optical nonlinearities than palladium naphthalocyanine compound results from the heavy metal atoms as central atom of naphthalocyanine lead compounds enhance the optical nonlinearities of naphthalocyanine compounds.