We report on the fabrication of laser-induced periodic surface structures in Cr films upon high repetition rate fs laser irradiation (up to 1 MHz, 500 fs, 1030 nm), employing beam scanning. Highly regular large-area () gratings with a relative diffraction efficiency of 42% can be produced within less than 6 min. The ripple period at moderate and high fluences is 0.9 μm, with a small period of 0.5 μm appearing at lower energies. The role of the irradiation parameters on the characteristics of the laser-induced periodic surface structures (LIPSS) is studied and discussed in the frame of the models presently used. We have identified the polarization vector orientation with respect to the scan direction as a key parameter for the fabrication of high-quality, large-area LIPSS, which, for perpendicular orientation, allows the coherent extension of the sub-wavelength structure over macroscopic distances. The processing strategy is robust in terms of broad parameter windows and applicable to other materials featuring LIPSS.
A simple route for the fabrication of dichroic optical structures based on Ag nanoparticles deposited onto SiO2 nanocolumns is presented. The strict control of the optical response is achieved after infrared laser treatment of the supported nanoparticles with a commercial nanosecond pulsed laser. Preliminary examples of the utilization of the laser-treated AgNPs/SiO2 nanocolumn system for optical recoding and encryption are shown.
1 May 2017 in International Journal of Hydrogen Energy
The two-way shape memory effect (TWSME), has been studied in a near-equiatomic NiTi commercial alloy. Two bending training methods have been applied on NiTi wires. One is based on the martensite deformation and the other on thermal cycling under constant bending curvature. The efficiency of each method has been evaluated with better results of TWSME in the martensite deformation method. Finite element simulation has been performed on wires, in the pure bending mode, in order to calculate the maximum tensile strain in the transversal section of the wire. These simulations have allowed us to compare our results with the TWSME data obtained in prior studies under the tensile mode.
27 September 2011 in International Journal of Applied Ceramic Technology