Linear and third-order nonlinear optical properties of conjugated diazobenzene oligomers


Jonathan L. Humphrey,, Kimberly M. Lott, and Darius Kuciauskas, Department of Chemistry, Virginia Commonwealth University, 1001 W. Main Street, Richmond, VA 23284
The potential use of materials with large third-order optical nonlinearity in important applications like photodynamic therapy and optical switching has driven decades of research into improving the nonlinear properties of organic molecules. These studies have found that extending the conjugation length of an organic chromophore is an effective means of increasing molecular third-order optical nonlinearity. In conjugated oligomers, this effect is of limited utility as the amplification saturates after the chain has been extended by several repeat units. Extending this mode of amplification would aid in the development of improved nonlinear materials. To this end, we have investigated the linear and nonlinear optical properties of conjugated oligomers of diazobenzene units with ethynyl linkages. These oligomers show no evidence of saturation over the length range of the study in both linear and nonlinear spectroscopies. The effective conjugation length is found to be greater than 36 repeat units.