SATURABLE ABSORPTION IN POLY(INDENOFLUORENE) - A PICKET-FENCE POLYMER

Poly(indenofluorene) shows a strong degenerate four-wave mixing (DFWM) response when it is excited with 100-fs pulses at 800 nm. The DFWM si gnal scales with the 1.5 power of the input intensity, which we interp ret as being due to absorption saturation phenomena. The saturation wa s studied by open-aperture Z scan in dilute solutions of poly(indenofl uorene) in chloroform. The changes in the absorption coefficient cu ar e described by the formula alpha = alpha(0)[1 + (I/I-sat)(1/2)], where I-sat is the saturation intensity, which is found to be of the order of 100 MW/cm(2). (C) 1998 Optical Society of America.