Nonlinear Optical Properties of Water-Soluble Polymeric Dyes with Biological Applications

The nonlinear optical properties of two water-soluble polymeric dyes, poly(R-478) (an anionic anthraquinone dye) and poly(S-119) (an anionic azo dye), are investigated utilizing nanosecond and femtosecond optical techniques such as z -scan, nonlinear transmission, and time-resolved luminescence. Poly(R-478) showed large nonlinear refraction when studied with femtosecond laser pulses at 800 nm, with a value for the intensity-dependent refractive index ( n I ) of 1.26 × 10 -4 cm 2 /GW. The thin film result at 1064 nm indicated a large nonlinear absorption in both polymeric dyes. The origin of the large fast optical nonlinearities in the polymeric system S-119 was investigated by probing the different functional groups of the polymer. The chromophore group (Sunset Yellow) of the S-119 polymer showed a smaller nonlinear response when compared to the polymer result. Significant differences in the electronic dynamics between the parent poly(S-119) and the chromophore Sunset Yellow were observed by time-resolved luminescence spectroscopy. The applications of the NLO effects in these polymers are demonstrated for laser ablation of A549 lung carcinoma cells.