Degenerate four-wave mixing of tunable dye laser pulses in good optical quality single crystal platelets of poly bis(p-toluene sulfonate) of 2, 4-hexadiyne-1, 6 diol (PTS) polydiacetylene was used to measure the spectral and temporal dependence of the material’s third order nonlinear optical susceptibility χ(3). For the wavelength range measured ‖χ(3)‖ varied from 9×10−9 esu at 6515 Å to 5×10−10 esu at 7015 Å. The material’s response time was determined to be less than the optical pulse width (≂6 ps) over this wavelength range.

The temporal response of the third-order nonlinear optical susceptibility in poly bis( p-toluene sulfonate) of 2,4-hexadiyne-1,6 diol was determined by time-resolved degenerate four-wave mixing using tunable dye laser pulses with 300 fs duration. In the material’s absorption region these experiments were combined with saturated absorption techniques yielding a measurement for the excited state lifetime of 1.8 ps. Off resonance the nonlinear response was determined to be optical pulse width limited.

We have developed a novel technique which utilizes the intensity-dependent dispersion relation of surface plasmons to study the third order nonlinear susceptibility coefficient χ(3). This new technique yields information about both the magnitude and the sign (with respect to χ(1)) of χ(3). Experimental results are reported for GaAs and Si at input wavelengths of 1.05 and 1.11 μm, respectively.