Two new organic dye samples J and L with a large two-photon absorption (TPA
) cross section have been reported. The linear absorption spectra show that
there is no linear absorption at the wavelength from 650 to 1200 mn. The m
olecular TPA cross section was measured to be as high as 2.59 x 10(-47) cm(
4.)s and 2.98 x 10(-47) cm(4.)s at 1064 nm for samples J and L, respectivel
y. The input-output curves indicate that there is a clear optical power lim
iting behaviour when the input intensity is higher than 0.4 GW/cm(2). Furth
ermore, the basic theory of the TPA process has been discussed.