Abstract
Suspensions of light-absorbing dielectric nanoparticles in liquid crystals (LCs) revealed a strong optical nonlinearity [1]. Metal nanoparticles (NPs) appeared to be also good dopants as absorbing particles due to a strong absorption in plasmon resonance band and high photostability. We report on the strong and fast cubic optical nonlinearity in the suspension of nematic LC E7 doped with the spherical mesogen-coated gold NPs [2] (core diameter, d ≈ 1.6 nm, concentration, c ≈ 0.5 wt %). The nonlinearity was observed by recording dynamic intensity sinusoidal gratings in planar aligned LC nanosuspension (thickness 55 μm). The gratings with the periods, Λ = 5 ÷ 50 μm, were recorded with two linear polarized pump beams (Ipump = 0 ÷ 50 W/cm2) with wavelength λpump = 532 nm being near plasmon resonance of the gold NPs. The efficiency of the first order diffraction, η, and characteristic times of the grating formation and relaxation, τ, were tested with a test beam (λtest = 632.8 nm) at different polarizations of the pump and test beams, grating period, and intensity. The square dependence of diffraction efficiency was observed (Fig.1) corresponding to a cubic nonlinearity of the material with the nonlinearity parameter and , and characteristic time of 1 ms.
© 2011 Optical Society of America
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