Authors: J. Spicer, K. See, Y. Katsumi, D. Zhang, J. Brupbacher and T. Vargo
Affilation: Johns Hopkins University, United States
Pages: 789 - 792
Keywords: optical behavior, linear, nonlinear, polymer matrix
The linear optical properties of a functionally graded, palladium nanoparticle reinforced fluorinated ethylene polymer matrix nanocomposite (PMNC) were investigated in this work. Synthesized through repeated infusions of a palladium organometallic precursor gas into an insulating, fully fluorinated polymer matrix film, the composite consists of discrete, palladium nanoparticles distributed throughout the polymer matrix. Under controlled processing conditions, preferential near-surface nucleation of nanoparticles can be achieved and, as a result of increases in nanoparticle density near the surface, percolation of the nucleated particles was observed. The presence of this near surface percolated layer significantly alters the optical properties of this materials system. To understand this behavior in detail, these materials have been characterized using Fourier transform infrared spectroscopy, X-ray photoelectron spectrometry, transmission electron microscopy. The reflectivity of the nanocomposites was investigated in depth and compared with the predicted behavior obtained from the Tourquato-Kreibig-Fresnel (TKF) model. The nonlinear optical properties of these materials have also been investigated using optical limiting experiments. Under relatively low fluence conditions, the palladium nanoparticles are excited to effectively change the nanocomposite into an efficient reflector as a result of plasma formation at the material surface. With plasma formation, optical transmission through the nanocomposite decreases significantly. Using a 8 ns laser pulse at 1064 nm, the measured transmission characteristics show that pulse fluences of nearly 1.3 x 104 mJ/cm2 reduced the transmission coefficient to less than 10% of the linear value.