The polarization holographic gratings recorded in Au nanoparticles-doped methyl orange/polyvinylpyrrolidone (MO/PVP) composite films were investigated. The polarization state of diffraction beams was controlled by a probe light and holographic gratings together. The first-order diffraction efficiency of the MO/PVP film doped with Au nanoparticles was measured to be 3.2 times larger than that of pure composite film. Meanwhile, an obvious enhancement of photoinduced birefringence of MO molecules was also demonstrated. This enhancement of diffraction efficiency and photoinduced birefringence was discussed in terms of the localized field effect via the surface plasmon resonance of Au nanoparticles, which was confirmed by finite-difference time-domain simulation.
The third-order nonlinear optical (NLO) properties of a series of fluoro-containing polyimides embedded with H-shaped chromophores including two donor-π-acceptor units were investigated by employing the single-beam Z-scan technique in the femtosecond regime. A strong nonlinear refraction index n2 on the order of 10−17 m2/W was acquired for the serial polymers at 810 nm laser pulses. The value of n2 was larger than that of the polymers with a corresponding mono donor-π-acceptor unit under the same laser excitation and negligible nonlinear absorption was observed in the two series of polymers at femtosecond pulse irradiation. The mechanism for the NLO response is discussed in terms of the molecular structure and dipole moment. We conclude that fluoro-containing polyimide polymers, with stronger electron-withdrawing substituents, embedded within H-shaped chromophores yield a noticeable improvement in the nonlinear refraction index. The figures of merit were evaluated for their potential applications in all-optical switching.
In this paper, patterning SiO2 thin film on the Si (100) surface was successfully demonstrated using a synchrotron radiation (SR) stimulated etching technique with SF6 + O2 as the reaction gas and a Co contact mask. The contact Co contact mask on the SiO2 surface was fabricated by sputtering Co film on a photolithography resist pattern and lift-off technique. The thickness of the Co mask measured using a step profile meter was about 145 nm. The SR irradiation with flowing SF6 and O2 can effectively etch the silicon dioxide and the etching process stop at the silicon surface. The etching rate was found to increase with decreasing the substrate temperature. The Co mask was found to show sufficient resistivity for the SR etching. The etched pattern was evaluated by scanning electron microscopy (SEM) and step profile meter.