Study of saturable absorption properties of graphite polymer composite films

[[abstract]]本論文使用石墨顆粒和聚合物的複合薄膜作為飽和吸收體，研究其非線性吸收特性。以PVA和石墨粉混和成溶液，製作不同濃度的石墨-PVA複合薄膜樣品，以輸出波長可調的OPO脈衝雷射系統研究石墨-PVA複合薄膜的飽和吸收效應，量測各個樣品在不同激發波長的穿透度與脈衝強度間的關係，結果顯示石墨顆粒濃度越大，會有較大的調制深度，較短波長的激發光有較大的調制深度，但要使石墨飽和所需要的光強度也會較大。 和其它研究文獻比較，本研究使用的石墨-PVA複合薄膜在低的激發強度就可看到飽和吸收的現象，我們算出石墨顆粒在樣品中的體積百分比分冸為0 17%、0 36%、0 57%，佔很小的比例，因此使石墨飽和所需要的光強度不大，只需要低的激發強度即可得到不錯的穿透度調制。[[abstract]]This study investigated the nonlinear absorption characteristics of graphite polymer composite films PVA and graphite powders were mixed with water to fabricate different concentrations of graphite-PVA composite film samples A wavelength-tunable optical parametric oscillation laser system was used to measure the dependence of the transmittance of the graphite-PVA composite films on the pulse intensity at various excitation wavelengths The results show that the films with larger concentrations of the graphite particles have greater modulation depth Shorter excitation wavelengths can obtain greater modulation depth but a larger intensity is needed to achieve saturation in graphite In comparison with other literature low excitation intensities were enough to achieve saturable absorption effect in this study The volume percentage of graphite particles in the samples were 0 17% 0 36% and 0 57% which accounted for a small proportion Therefore low excitation intensities were enoughto get good modulation of optical transmittanc