| Abstract [eng] |
Saulius Vaisiūnas, The Investigation of Photomodification and Optical Resistance on Laser Irradiation Wavelength In Polymers. Two photon polymerization technology is one of the most promising fields of laser physics today. However, many experiments are limited to a two-phonon polymerization phenomenon study and the delivery of business-oriented derivatives. The main reason for this is the limited technical ability to select the desired parameters. As for the physical polymerization mechanism, the main wave lengths (515 nm, 800 nm, 1030 nm) are commonly used for laser writing. However, no studies have been carried out that describe the processes taking place in the precursors of photosensitive polymerization of polymers by consistently varying laser beam wavelengths. To complete this research gap and to get a better understanding of the origin of polymerizations, this non-reflective study is carried out. The z-scan open and closed aperture method is used based on a continuous experiment. The experiment uses a 175 fs pulse duration Yb: KGW synchronized mode pulsed Pharos laser produced by Light Conversion. Also, the parametric amplifier Orpheus and the second harmonic generator "Lira". At the same time, this system can generate radiation in the range of 310-2600 nm. The work maintains a constant frequency of 400 kHz pulse repetition. The range of 350 - 1120 nm wavelengths is also selected. The evaluation of the results are based on the radiation transmition function mentioned in the literature. The approximation of these functions determines nonlinear absorption coefficients and their variation with respect to the radiation wavelength. According on their wavelength dependence, the influence of different photon absorption mechanisms has been determined and confirmed for the polymerization reaction. The wavelength range 375 – 975 nm is dominated by the single photon absorption acquired by measured linear absorption spectrum of the sample. In 530 - 790 nm, the two - phonon absorption polymerization mechanism predominates using a z-scan open aperture method. The 790 - 975 nm wavelength range increases the absorption efficiency of the three photons, while the absorption efficiency of the two photons decreases. These are results that describes the origin of polymerization reaction in the range of 375 nm to 975 nm in different wavelengths. |
