We have developed an all-optical method to control the in- and out-of-plane spatial orientation of nematic liquid crystal
(NLC) molecules by leveraging the highly localized electric fields produced in the near-field regime of gold nanoparticle
(AuNP) layers. A 1-2 micron thick NLC film is deposited on a close-packed drop-cast AuNP layer, excited with tunable
optical sources and the transmission of white light through it analyzed using polarization optics as a function of incident
light wavelength, excitation power and sample temperature. Our findings, supported by simulations using discrete-dipole
approximations, establish the optical switching effect to be repeatable, reversible, spectrally-selective, operational over a
broad temperature range, including room temperature, and requiring very small on-resonance excitation intensity (0.3
W/cm2). For the case of the in-plane switching we have additionally demonstrated that controlling the incident excitation
polarization can continuously vary the alignment of the NLC molecules, allowing for grayscale transmission.
Makiko T. Quint, Silverio Delgado, John H. Paredes, Linda S. Hirst, and Sayantani Ghosh, "Optical switching of nematic liquid crystal film arising from induced electric field of localized surface plasmon resonance," Proc. SPIE 9547, Plasmonics: Metallic Nanostructures and Their Optical Properties XIII, 954729 (Presented at SPIE Nanoscience + Engineering: August 13, 2015; Published: 28 August 2015); https://doi.org/10.1117/12.2186197.
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