Abstract

The standard electric-field-induced second-harmonic (EFISH) technique for measurement of the first hyperpo larizability ( b ) of nonlinear optical molecules is limited by the fact that the second hyperpolarizability ( g ) also contributes to the second-harmonic signal from which b is deduced. We present a modified time-resolved EFISH in which the first and the second hyperpolarizabilities can be determined separately and accurately in the same experiment. We studied para-nitro aniline dissolved in a highly viscous solvent, glycerol, under conditions whereby the electric field was applied faster than the characteristic time for molecular rotation. This technique enabled the g contribution to the signal to be resolved separately from the b contribution. The results confirm that for this molecule g contributes only ~10% of the total EFISH hyperpolarizability.

© 2001 Optical Society of America