| Summary: | 碩士 === 國立中正大學 === 物理系 === 87 === In this thesis, we used Z-scan technique with a frequency doubled, Q-switched and mode-locked Nd:YAG laser operating in mode to investigate the nonlinear optical properties in a chloro-aluminum (ClAl) Phthalocyanine (Pc) solution and a a carbon-60 solution respectively.
For chloro-aluminum (ClAl) phthalocyanine (Pc) dissolved in ethanol or methanol, dubbed as CAP, we found the nonlinear absorption to be repetition rate dependent when the input energy is relatively high. The observed transmittance around the focus is higher when the laser ran at lower repetition rates (1Hz) than at high repetition rates (5Hz and 10 Hz). This is attributed to heat induced natural connection whose recover time is in the order of tenth seconds.
Using the same apparatus and the same technique, we also investigated the nonlinearities in a Carbon 60 solution. Using single picosecond pulses out of the laser, we observed positive nonlinear refraction due to electronic transition. Using the full pulse trains, a sign change of nonlinear refraction relative to that of single pulse excitation is observed, and is attributed to the heat-induced temperature rise and the population relaxing to C60’s triplet states.
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