Directional Selective Nonlinear Transmission of Femtosecond Pulses in Glass-Metal Nanocomposites

Summary form only given. Third-order nonlinear optical materials have gained special attention due to their unique role in all optical switching, optical limiting and optical communication applications. Composite materials based on nanoparticles (NP) in transparent matrix proved to be promising candidates whose χ⁽³⁾ can be adequately tailored by tuning the material parameters such as size, shape, and filling factor of nanoparticles [1].The samples studied are metallic nanocomposites consisting of glass containing spherical silver nanoparticles (Ag NP) arranged in a two-layer geometrical structure.

The nanoparticles are distributed within a thin surface layer of glass of thickness few microns, while the remainder of the sample thickness (1mm), consists of pure soda-lime silicate glass (SLSG). A femtosecond Z-scan technique has been used for nonlinear characterization. In general one measures the transmission change as a function of intensity [2].

A Ti:Sa laser (wavelength λ=800nm, pulse duration τ=100fs, repetition rate 1kHz) is used as excitation source. The excitation at 800nm pump wavelength results in considerable two-photon absorption (2PA) for Ag NPs due to their surface plasmon resonance (at 410nm), whereas glass UV absorption requires at least three photons absorbed simultaneously.

To investigate the nonlinear properties of these two-layer systems thethe Z-Scan measurements are performed by irradiating from particle as well as substrate side of the sample [3].