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Interaction between Self Phase Modulation and Positive Group Velocity Dispersion in PMMA Polymer for Simplified Thin Film Compressor of High-Intensity Ultrashort Laser Pulses
Y.S. Nada, J.M. El-Azab, H. Othman, T. Mohamad, S.M.A. Maize

We report on using Polymethyl Methacrylate (PMMA) polymer as a broadening material for high-intensity femtosecond laser pulses. The broadened pulse is recompressed using compressor such as pair of gratings or chirped mirrors in order to achieve simplified thin-film compressor with compression factor of 11. The Nonlinear Schrödinger Equation (NLSE) is solved numerically to examine the combined effect of normal group velocity dispersion (GVD) and self-phase modulation (SPM) in PMMA polymer. The effects of PMMA polymer thickness and input pulse intensity on the broadening factor are studied. It is noticed that higher time broadening factors could be obtained by increasing the input intensity and using larger thicknesses of PMMA. Depression of Small Scale Self Focusing (SSSF) effect is discussed in order to achieve the optimum conditions of laser pulse compression. Lower B-integral values are corresponding with input pulse intensities lower than 1 TW/cm2 and polymer thickness shorter than 100 μm.

Keywords: PMMA, self-phase modulation, self-focusing, group velocity

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