Synthesis and nonlinear optical properties of Lif films containing gold nanoparticles

Abstract

We have studied the structure and optical properties of a thin lithium fluoride (LiF) film containing nanosized gold particles, which has been obtained by the thermal evaporation of LiF and Au followed by deposition onto the surface of a glass substrate heated to 590 K. Data of scanning electron microscopy and X-ray diffraction (XRD) showed that the composite film possesses a polycrystalline structure with an average LiF grain size of about 170 nm. The formation of gold nanoparticles in the film was confirmed both by XRD data and the presence of plasmon resonances in the optical absorption spectrum, which is close to the spectra obtained by model calculations for a LiF matrix with 20- to 40-nm-sized gold particles. Using the Z-scan technique, it is shown that the composite film exhibits nonlinear absorption of pulsed laser radiation with a wavelength of 780 nm and pulse duration of 150 fs at a power exceeding 100 mW. The magnitude of this effect is comparable to that observed previously for various single-crystalline matrices containing gold nanoparticles.