Absorption spectra and second-harmonic generation of Langmuir–Blodgett monolayers containing a hemicyanine dye with a large second-order hyperpolarizability are reported. The dye is found to be in the form of H aggregates in a pure-dye film and mostly monomeric in a 1:4 dye–arachidic acid film. This observation explains a report in the literature that mixed dye–arachidic acid films display greater second-harmonic generation efficiency than a pure-dye film. It may also be a factor in the reported failure of second-harmonic generation to increase quadratically with the number of layers in noncentrosymmetric multilayer films.
© 1988 Optical Society of America
Original Manuscript: August 19, 1987
Manuscript Accepted: October 30, 1987
Published: February 1, 1988
J. S. Schildkraut, T. L. Penner, C. S. Willand, and A. Ulman, "Absorption and second-harmonic generation of monomer and aggregate hemicyanine dye in Langmuir–Blodgett films," Opt. Lett. 13, 134-136 (1988)