Search

Graphical abstract:

Nonlinear optical properties of metallic and oxide metallic nanoparticles have been extensively studied as saturable absorbers in fiber-optic lasers in the infrared region for the generation of short and/or ultrashort pulses. In this paper, we report an experimental study of the nonlinear optical response of silver and zinc nanoparticles for continuous-wave illumination at 1550 nm. Nonlinear absorption was investigated using the power-dependent transmission and Z-scan techniques. The results obtained from the first technique showed that the zinc and silver particles behave like saturable absorbers, the modulation depths obtained were 15 % and 32 %, respectively. The Z-scan technique showed the presence of nonlinear refraction and absorption in both samples, the open aperture configuration confirmed the behavior of the materials as saturable absorbers. Additionally, the nonlocality of the nonlinear response was analyzed using a numerical model.

The radiation pressure forces for Au nanoparticles in the Rayleigh regime under the influence of a coherent source of infrared light from 0.7-1.5 m of a Gaussian beam with fundamental mode corresponding to the TEM00mode are studied. An intensity distribution of the source in terms of the spot size and power are considered to analyze the gradient, scattering and absorption forces on a sphere located arbitrarily on a Gaussian beam. The results have shown, through an analysis stability, the optical manipulation is better suited for longer wavelengths, small particles, and a beam waist significantly reduced.

By using the Hot Filament Chemical Vapor Deposition (HFCVD) technique tungsten thin films were deposited on amorphous quartz substrates. To achieve this, a tungsten filament was heated at 1300 °C during 30 minutes maintaining a constant pressure inside the chamber at 460 mTorr and substrate at 700 °C. Transition from tungsten oxide deposits to tungsten thin films, by varying the substrate temperature, were characterized by means of Scanning Electron Microscope (SEM), Atomic Force Microscope (AFM), X-Ray Diffraction and, micro-Raman spectroscopy. The SEM micrographs reveal that the tungsten films have no more than 200 nm in thickness while XRD show evidence of the films crystallize in the á-tungsten modification. On the other hand, AFM shows that the tungsten thin films exhibit a uniform and smooth surface composed with semi-spherical shapes whose diameters are below than 50 nm. Furthermore, to the naked eye, the as-deposited tungsten films exhibit a high mirror-like appearance.