Search

Nonlinearity-induced asymmetric diffraction based on spatial self-phase modulation is demonstrated experimentally through the illumination of a focus Gaussian laser beam on azo-containing materials coupled together with an A/B structure. We report here that symmetry breaking occurs to the intensity distribution of the transmitted light with diffraction rings when the propagation direction of the pump light is reversed, where asymmetric diffraction excitation takes place. In certain cases, unidirectional diffraction excitation could be realized. In addition, as the light intensity is enhanced, the diameter of the diffraction pattern increases linearly and the linear coefficient is related to the propagation direction of the beam. The diffraction efficiency of the nth diffraction ring differs significantly between the two directions when incident light is set in some specific intensity range. The achievement of the symmetry breaking of light propagation is attributed to the different nonlinear optical response strength of the two azo-containing materials. [ABSTRACT FROM AUTHOR]

Area-selective deposition of self-assembled monolayers (SAMs) has been demonstrated on patterns of SiO2/Si(100). The pattern was fabricated by synchrotron radiation stimulated etching of SiO2 thin films on Si substrate. Several kinds of the patterns were obtained with different types of masks. A dodecene SAM was deposited on Si surface and an octadecyltrichlorosilane SAM was deposited on SiO2 surface. The deposited SAMs were densely packed and well ordered characterized by infrared spectroscopy, ellipsometry, and water contact angle measurements. [ABSTRACT FROM AUTHOR]

The nonlinear absorption and optical limiting properties of a chiral polymer were investigated by employing Z-scan technique in femtosecond regime. Reverse saturable absorption was observed in the polymer at 800 nm and the nonlinear absorption coefficient of 5.97 cm/GW was obtained at the irradiance of 2.75 GW/cm2. The nonlinear absorption coefficient versus the input irradiance was measured to meet a linear increasing function, giving evidence of two-photon induced excited-state absorption existing. Particularly, the chiral polymer was shown to possess a large ratio (∼251) of excited-state to ground-state absorption cross-section and a remarkable optical limiting behavior was achieved in it. [ABSTRACT FROM AUTHOR]