[OPTICAL REVIEW Vol. 17, No. 3 (2010) 346-351]
© 2010 The Japan Society of Applied Physics

Mechanism for Giant Electro-Optic Response of Porphyrin J-Aggregates in Polymer Film and Aqueous Solution

Kazuaki NAKATA1, Takayoshi KOBAYASHI2, and Eiji TOKUNAGA1,3*

1Department of Physics, Faculty of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjukuku, Tokyo 162-8601, Japan
2Department of Applied Physics and Chemistry, Institute for Laser Science, The University of Electro-Communications, 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585, Japan
3Research Center for Green Photo-Science and Technology, Tokyo University of Science, 1-3 Kagurazaka, Shinjukuku, Tokyo 162-8601, Japan

(Received September 19, 2009; Accepted December 15, 2009)

We report the dependence of the polarizability difference Δα on the orientational distribution of porphyrin J-aggregates. For quasi-one-dimensionally oriented aggregates in a polymer film, the red shift in YF configuration was about 2 to 3 times smaller than that in YF configuration, where Y is the orientational direction of the J-aggregates and F is the applied AC electric field vector. For an aqueous solution where J-aggregates were three-dimensionally oriented, the exciton band showed an electric-field-induced broadening. In addition, a red-shifted signal for two-dimensionally oriented aggregates in the polymer film was reduced by one order of magnitude at 77 K compared with that at room temperature. These results were explained reasonably well by the molecular rearrangement model, which was applied to a variety of orientational distributions.

Key words: porphyrin, J-aggregate, static polarizability, Frenkel exciton, electroabsorption, electrooptic effect, Kerr effect, polymer film, aqueous solution, orientational distribution

*E-mail address: eiji@rs.kagu.tus.ac.jp