Poly degenerate four-wave mixing

To date, results have only been acquired for the ethoxy-substituted poly(ester) with a pentamethylene spacer. A 2.5 pm film produced a third-harmonic signal at 632.8 nm 29 times the intensity of a quartz signal, corresponding to a of approximately 8 x 10 13 esu. Degenerate four-wave mixing experiments are underway on this and other materials, and preliminary results are comparable to the values from third harmonic generation. 

Poly(3-alkyl-a-thiophene) systems show significant third-order nonlinear susceptibilities ( ) Though, oligothiophenes have been studied for their third-order susceptibilities, accurate third-order optical nonlinearity data obtained by degenerate four-wave mixing or electric-field-induced second harmonic generation (EFISH) are difficult to attain reliably on samples with poor solubility characteristics (92MM1901). 

The temporal response of the third-order nonlinear optical susceptibility in poly(PTS) crystal was determined by time-resolved degenerate four-wave mixing (DFWM) by Carter and coworkers. The excited lifetime T ws measured to be 1.8 0.5 ps at 652 nm in the resonant region. The values of phase relxation time T2 measures by Hattori and Kobayashi for a cast film of poly(3BCMU) were 30 and 90 fs for the respective incident... 

Amorphous PDAs. Yu et al.(2i) prepared poly(hexa-2,4-diynylene terephthalate), which is not photosensitive, but does polymerize by heating at 150 C. A value of 3.2 X 10 ° esu (determined the degenerate four wave mixing technique at 532 nm) has been reported for this material The polymers 3 and 4 (Chart 4) are not photosensitive, but underwent cross-polymerization when heated at 180°C (in the molten state) for 2.5 hours with simultaneous UV irradiation, giving red transparent materials. The x values for these materials were found to be 1.9 - 3.5 x 10 ° esu for polymers 3 and 2.7 -2.9 x 10 esu for polymers 4. Absorption spectra of one of the polymers 4 are shown in Figure 3. The films have an absorption maximum at 400 nm and a trough at 340-350 nm, but absorption tails down towards 700 nm due to their amorphous nature. 

B. P. Singh, P. N. Prasad, F. E. Karasz, Third-Order Non-hnear Optical Properties of Oriented Films of Poly(p-Phenylene Vinylene) Investigated by Femtosecond Degenerate Four Wave Mixing. Polymer 1988,29,1940-1942. 

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