Investigation of third-order nonlinearity of an azo dye and its metal-substituted compounds

The real part of third-order optical nonlinearity of an azo dye (2-(2-thiaz olylazo)-5-diethylaminophenol TAEP) and those of its copper- and cobalt-sub stituted compounds are measured by using femtosecond optical heterodyne opt ical Kerr gate technique at the wavelength of 647 nm. All the values are fo und to be negative. Those of Cu- and Co-substituted compounds are found to be larger than that of the metal-free dye by two and three orders of magnit ude, respectively. A negative gamma (eff) as large as 10(-29) esu is found in Co complex. We use a three-level model to characterize the nonlinear pro cess, and suggest that pi -electron delocalization in metal complex leads t o an enhancement. (C) 2000 Elsevier Science B.V. All rights reserved.