Transition metal poly-ynes have previously been demonstrated to possess large third-order susceptibility.1 This nonlinearity arises from the presence of extensive electron delocalization in the individual repeat units of the polymer chain. To further enhance the nonlinearity, we synthesized the series of polymers shown in Table I. We attempted to increase the electron delocalization in the repeat units of these polymers by incorporating pyridine and naphthalene in place of the more usual benzene rings. The number of diethynylarenes in the repeat units in some of the newly synthesized materials was increased from 1 to 2. Both of these changes were found to increase the nonlinearity substantially (by factors of 2 or more). Thin films of good optical quality were fabricated from the polymers, and their nonlinearities were measured. The imaginary part of the susceptibility was dominant over the real part. A two-photon absorption coefficient of about 2 cm/MW was measured in one of the films. We then performed an optical switching experiment with-one of the polymers in a pump-probe arrangement.
© 1991 Optical Society of AmericaPDF Article