RESUMEN
In the present research diamond-like carbon (DLC) films containing 4-29 at.% of silicon were deposited by reactive magnetron sputtering of carbon target. Study by X-ray photoelectron spectroscopy revealed the presence of Si-C bonds in the films. Nevertheless, a significant amount of Si-O-C and Si-Ox bonds was present too. The shape of the Raman scattering spectra of all studied diamond-like carbon containing silicon (DLC:Si) films was typical for diamond-like carbon. However, some peculiarities related to silicon doping were found. Studies on the dependence of DLC:Si of the optical transmittance spectra on the Si atomic concentration have shown that doping by silicon affects linear, as well as nonlinear, optical properties of the films. It is shown that the normalized reflectance of DLC:Si films decreased with the increased exciting light fluence. No clear relation between the normalized reflectance and photoexcited charge carrier relaxation time was found. It was suggested that that the normalized reflectance decrease with fluence can be related to nonlinear optical properties of the hydrogenated diamond-like carbon phase in DLC:Si film.
RESUMEN
In the present research, hydrogen-free diamond like carbon films with embedded copper nanoparticles (DLC:Cu) were grown by simultaneous DC magnetron sputtering of the graphite and copper targets. X-ray photoelectron spectroscopy was used to define the composition of the samples. Atomic force microscopy studies of diamond, like carbon films containing different amount of copper, revealed wide range of the surface morphologies as well as sizes and shapes of the embedded copper nanoclusters. Raman scattering spectra of all the DLC:Cu films investigated were typical for diamond-like carbon (including samples containing more than 60 at.% of copper). sp3/sp2 carbon bond ratio in the films decreased with the increase of the Cu amount in the films. According to the optical absorbance measurements, the surface plasmon resonance related absorption peak of DLC:Cu films was only detected in the films containing 28.45 at.% Cu. For the diamond like carbon films containing more than 40 at.% Cu, a further increase of Cu amount in the nanocomposite resulted in minor changes of the absorbance spectra. Some correlation between the changes of the samples surface morphology as well as phase structure and optical absorbance spectra of the films was found. In all cases, reverse-saturable absorption of the DLC:Cu films was observed. For some DLC:Cu films damage of the sample occurred at higher light fluences that can be related to the heating that is caused by the surface plasmon resonance effect.
RESUMEN
We numerically and experimentally demonstrate a Yb-doped fiber ultrashort pulse generator based on self-phase modulation and alternating spectral filtering, operating at a wavelength of 1060 nm and providing a stable ultrashort pulse train. Pulses with energy up to 2.8 nJ were generated experimentally and were limited only by available pump power.