[OPTICAL REVIEW Vol. 7, No. 6 (2000) 489-494]

Femtosecond Time-Resolved Third-Order Nonlinear Response of4-(N, N-Diethylamino)-β-Nitrostyrene Solutions in the NonresonantRegion --Experimental Evidence of Group-Velocity Dispersion Effect--

Yoshihisa YAMAOKA1, Ryuji MORITA1,2 and Mikio YAMASHITA1,2

1Department of Applied Physics, Hokkaido University, Kita-13, Nishi-8, Kita-ku, Sapporo, 060-8628 Japan, 2CREST, Japan Science and Technology Corporation (JST), Kawaguchi Center Building, 1-8, Honcho 4-chome, Kawaguchi, Saitama, 332-0012 Japan

(Received November 5, 1999; Accepted August 2, 2000)

We measure the femtosecond time-dependent, third-order nonlinear optical response for 4-(N, N-diethylamino)-β-nitrostyrene (DEANST) dissolved in N, N-dimethylformamide (DMF) from 0.1 to 1.4 M concentrations in the nonresonant region using time-resolved degenerate four-wave mixing (DFWM) spectroscopy. It is found that the DFWM signal profile with delayed responses depends on the concentration. This concentration dependence is determined to be mainly due to the group-velocity dispersion effect of the DEANST solution at the high concentration and the nonlinear response of the DMF solvent at the low concentration, but not due to the change in third-order nonlinear response of DEANST itself.

Key words : femtosecond third-order nonlinearity, group-velocity dispersion, delayed nonlinear response, femtosecond time-resolved degenerate four-wave mixing, second hyperpolarizability