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DF: Fachverband Dielektrische Festkörper

DF 6: Optical and nonlinear optical properties, photonic

DF 6.5: Vortrag

Dienstag, 15. März 2011, 12:00–12:20, MÜL Elch

Polarization controlled switching of optical nonlinearity in nanocomposite glass — •Sabitha Mohan and Gerhard Seifert — Physics Institute, Martin-Luther-Universität Halle-Wittenberg, von-Danckelmann-Platz 3, 06120 Halle (Saale)

Nonlinear optical properties of uniformly oriented anisotropic metal nanoparticles in a glass matrix are studied using the Femtosecond Z-Scan technique. The glass samples (thickness 200µm) contain spheroidal nanoparticles only in a thin surface layer of 1-2 micrometer thickness. The macroscopic structural anisotropy of the composite system allows to tailor the optical nonlinearities of longitudinal and transverse Plasmon band separately. Ultrafast excitation of the longitudinal plasmon band (peak at  550 nm) in the near-resonant regime with 1030nm excitation wavelength (280fs pulse duration, 1 kHz repetition rate) results in a saturable absorption along with a negative nonlinear refraction. Contrastingly in the non-resonant regime the excitation results in a positive nonlinear refraction with negligible nonlinear absorption, which stems from the pure glass substrate. The contribution from the transverse plasmon band is observed by tuning the excitation wavelength to 800nm (pulse duration τ=80fs, 1 kHz repetition rate) which is in two-photon absorption resonant with the transverse plasmon band (peak at  390 nm). Studying samples with different aspect ratio, we obtained the dispersion of third-order nonlinearity in the near resonant regime, showing a boosting of the nonlinear processes due to the dielectric field enhancement.