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ABSTRACT: A single-layer of breath figure pattern was explored via the dynamical optical images and the temperature evolution. The pattern was prepared with the solution of carbon disulfide (CS(2)) dissolved 1% weight concentration of polystyrene. The evaporation of CS(2) was considered to be the most important role to the formation of the breath figure pattern. The understanding of the breath figures pattern will promote the technique to fabricating an imprinted template with demanded hexagonal structures.
Optics Express 08/2010; 18(17):18464-70. · 3.59 Impact Factor
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ABSTRACT: Diffraction behavior of cholesteric liquid crystal (CLC) grating with the surface plasmon effect was investigated. One indium tin oxide plate of the CLC grating cell was covered with silver nanoparticles. With the application of a proper voltage, a well formed phase grating was constructed in the CLC cell. The CLC grating was probed by a beam of the polarized-monochromatic light, and the wavelength range was from 450 to 700 nm. It was shown that an extra first-order diffraction band was observed around 505 nm. The physical reason of the extra diffraction band could be the surface plasma effect emerged from silver nanoparticles. The extra diffraction band due to the surface plasmon effect can offer potential applications in nano-optics, such as the optical switch function.
Journal of Applied Physics 10/2008; · 2.17 Impact Factor
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ABSTRACT: We report the results of our experimental investigation of laser induced gold nanoparticle gratings and their optical diffraction properties. A single shot of a pair Nd-YAG laser pulses with the same polarization is directed toward a 6 nm thick gold film on a substrate of polymethyl methacrylate. As a result of the laser illumination, the thin gold film is fragmented into an array of nanoparticles. Through the observation of scanning electron and dark-field optical microscopes, we discovered that the morphology of the gold nanoparticle grating is dependent on the fluence of laser pulse. The spectrum of first order diffraction shows the dependence on the absorbance property due to the presence of the nanoparticles. The ablation of nanothickness thin films via the use of laser pulses may provide a simple and efficient method for the fabrication of nanoscale structures, including two dimensional arrays of nanoparticles.
Applied Physics Letters 08/2008; 93(6):061109-061109-3. · 3.84 Impact Factor
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ABSTRACT: This study investigates the optical nonlinearity of beam propagation in homogeneously aligned nematic liquid crystal (NLC) cells at a temperature close to the nematic-isotropic temperature (TNI). The undulate propagation mode with convergent and divergent loops appearing alternately is reported and the thermally enhanced optical reorientation nonlinearity at the focus is described. The optically induced phase transition exists along the pump beam direction. With the application of the conscopic technique, the arrangements of LC at the focus are proposed in this study. Results of this study demonstrate that the evolution of the LC configuration was affected by the pump beam based on the analysis of conoscopic patterns.
Optics Express 04/2008; 16(6):4078-84. · 3.59 Impact Factor
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ABSTRACT: A simple and accurate measurement method for determining the cell parameters of a twisted nematic liquid-crystal display (TN-LCD) is proposed. Based on the measurement of the maximum reflectance and the maximum transmittance of a TN-LCD by rotating the polarizer at a particular angle, between the front director of the liquid crystals and the transmission axis of the polarizer, the cell gap and the twist angle can be determined according to the Jones matrix theory, and the twist sense can also be determined easily by applying an external small voltage to slightly change the effective refractive index of the liquid crystal.
Applied Optics 07/2007; 46(17):3493-7. · 1.41 Impact Factor
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ABSTRACT: Periodic surface plasmon-enhanced diffraction effect in cholesteric liquid crystal (CLC) grating is demonstrated. The CLC grating is a periodic structure and results in the excitation of a periodic surface plasmon. The surface plasmon-enhanced diffraction effect may be important in nano-optics applications.
Lasers and Electro-Optics, 2007. CLEO 2007. Conference on; 06/2007
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ABSTRACT: The authors report the observation of an enhanced optical diffraction in cholesteric liquid crystals (CLCs) due to the presence of silver nanoparticles. The silver nanoparticles are deposited on the surface of one of the indium tin oxide electrodes of the CLC cell. With the application of a proper voltage, the liquid crystals assume its cholesteric phase with the helical axis perpendicular to the applied electric field. The CLC grating was probed by a beam of polarized light in the spectral range from 450 to 750 nm. The direction of propagation of the beam is perpendicular to the helical axis of the liquid crystals. The authors report a significant enhancement in the first-order diffraction efficiency at around 543 nm. The results of the experimental observation are presented and discussed.
Applied Physics Letters 05/2007; 90(18):183115-183115-3. · 3.84 Impact Factor
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ABSTRACT: A multiguide directional coupler with a gratinglike indium-tin-oxide electrode on a planar nematic liquid-crystal film is studied. The linearly polarized beam can be coupled into adjacent channels with the periodic modulation of the refractive index by applying a periodic electric field. The intensity distribution of coupling in the transverse direction varies with the distance of beam propagation. The coupling effects, which depend on the polarization of the incident beam and the temperature of the liquid crystals, are also discussed.
Journal of Applied Physics. 05/2005; 97(10):103113-103113-4.
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ABSTRACT: A voltage-controllable multiguide directional coupler is designed with a nematic liquid crystal cell, comprising a grating-like indium-tin-oxide electrode. An incident polarized laser beam can couple into adjacent channels by periodic distribution of the refractive index. This capability is attributed to the reorientation of the periodic liquid crystal caused by the application of a voltage. The coupling variation of the optical power in the transverse direction parallel to the waveguide surface is investigated. This work presents a promising coupling function for potential applications of optical communication devices.
Applied Physics Letters 08/2004; 85(6):855-857. · 3.84 Impact Factor
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ABSTRACT: We address the reorientational optical nonlinearity of homogeneously aligned neamtic liquid-crystal (NLC) cells. The propagation of light in NLC cells depend strongly on temperature. At a temperature approaching the clearing point, an undulating beam and multifocal points are observed in the NLC cell by use of a polarizing optical microscope. Using a conoscopic technique, we observed novel consecutive concentric and parabolic patterns projected onto a screen. Optical energy is considered to compete with thermal energy to affect NLC's orientation and to generate singularities in the steady state. A model of the configuration of the liquid crystal's orientation is proposed.
Optics Letters 01/2004; 28(23):2357-9. · 3.40 Impact Factor
