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Phase-induced polarization modulation has been achieved experimentally by means of the all-optical holographic method. An extra spiral phase is added to a Gaussian beam and then a holographic grating is recorded through the interference of a Gaussian beam and the phase-vortex beam with the same linear polarization state in an azobenzene liquid-crystalline film. We report here that the polarization state of the diffraction light from the recorded grating is different from that of the incident light, while no polarization variation occurs for the holographic grating recorded by two Gaussian beams. The phase-induced polarization modulation is mainly attributed to the formation of birefringence in the film generated by phase vortex, which is investigated through the ripple patterns resulting from the competition between photoinduced torques and analysed by the Jones matrix. The experimental results could enrich the connotation between optical parameters and offer a method to realize polarization modulation through phase control. [ABSTRACT FROM AUTHOR]

Abstract: The nonlinear absorption of an azo-containing ion liquid crystal polymer, in dimethylformamide solution or solid thin film, has been investigated using Z-scan technique. Under the excitation of nanosecond or picosecond pulses at 532nm, the film presents large saturable absorption (SA), while the solution shows reverse saturable absorption. The alteration of nonlinear absorption behavior is due to the change of excited state cross-section and the time of intersystem crossing in solution and film. Irradiated by a continuous wave laser, SA is observed in both solution and film due to the low excitation optical intensity and thermal effect. [ABSTRACT FROM AUTHOR]

Abstract: Colloidal Au and colloidal Ag were prepared by chemical reaction method and the nonlinear optical properties of Au and Ag nanoparticles doped polyvinylpyrrolidone (PVP) composite films were investigated using Z-scan technique with 38 ps pulses at 532 nm. Open aperture Z-scan measurements indicated that both the Au/PVP and Ag/PVP composite films exhibited reverse saturable absorption. Nonlinear absorption coefficients and third-order nonlinear refractive indices were determined. The mechanisms accounting for the process of nonlinear refractions were analyzed and the figures of merit W and T of the Au/PVP and Ag/PVP composite films were evaluated. [Copyright &y& Elsevier]

Abstract: The nonlinear refraction and photoinduced birefringence of chlorophosphonazo I (CPA I ) doped PVA thin films were investigated. The single-beam Z-scan measurement showed that CPA I doped PVA thin film possessed a large value of nonlinear refractive index (n 2=1.82×10−12 cm2/W) under a pulse 532nm excitation, and the mechanism accounting for the process of nonlinear refraction was discussed in term of resonant electronic effect. Moreover, fast and stable molecular reorientation was observed when investigating the photoinduced birefringence of CPA I doped PVA thin film with a CW 532nm laser as pump light and a CW 650nm laser as probe light. [Copyright &y& Elsevier]

Abstract: Patterning SiO2 thin film on the Si (100) surface was demonstrated by synchrotron radiation (SR) stimulated etching with a contact cobalt mask. The reaction gas was a mixture of SF6 and O2. The contact cobalt mask was fabricated by sputtering cobalt films on a photolithography resist pattern and lift-off technique. The thickness of the mask was about 145nm. The SR irradiation with flowing SF6 and O2 could effectively etch the silicon dioxide and the etching process stopped at the SiO2/Si interface. The etching rate at room temperature was about 2.7nm per 100mAmin. The etched pattern was evaluated by scanning electron microscopy (SEM), atomic force microscopy (AFM) and step profile meter. Area-selective and anisotropy etching were achieved and the roughness (Ra) with a line profile on the etched surface was about 0.05nm. [Copyright &y& Elsevier]

A nano-pattern of SiO2 on a Si (100) surface has been demonstrated by synchrotron-radiation-stimulated etching with a tungsten nano-pillar mask. The reaction gas was a mixture of SF6 and O2. The mask was fabricated using a focused ion beam with W(CO)6 as the source gas. The width and height of the tungsten nano-pillar were ∼80 nm and 160 nm, respectively. Synchrotron radiation irradiation with flowing SF6 and O2 effectively etches the silicon dioxide, and the etching process followed the surface photochemical reaction. The etched surface was very flat, and no undercutting occurred during the etching process. [ABSTRACT FROM AUTHOR]