Browsing by Subject "Laser materials processing"

Now showing 1 - 3 of 3
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    Direct laser interference patterning of diffraction gratings in Safrofilcon-A hydrogel: fabrication and hydration assessment
    (MDPI, 2021-02-24) Daniel Sola; Sola Martínez, Daniel; Milles, Stephan; Lasagni, Andrés F.; Física
    Refractive index modification by laser micro-structuration of diffractive optical devices in ophthalmic polymers has recently been applied for refractive correction in the fields of optics and ophthalmology. In this work, Safrofilcon-A hydrogel, used as soft contact lenses, was processed by direct laser interference patterning (DLIP) to fabricate linear periodic patterns on the surface of the samples. Periodic modulation of the surface was attained under two-beam interference by using a Q-switched laser source with emission at 263 nm and 4 ns pulse duration. Features of processed areas were studied as a function of both the interference spatial period and the laser fluence. Optical confocal microscopy used to evaluate the topography of the processed samples showed that both structured height and surface roughness increased with laser fluence. Static water contact angle (WCA) measurements were carried out with deionized water droplets on the structured areas to evaluate the hydration properties of DLIP structures. It was observed that the laser structured areas induced a delay in the hydration process. Finally, microstructural changes induced in the structured areas were assessed by confocal micro-Raman spectroscopy showing that at low laser fluences the polymer structure remained almost unaltered. In addition, Raman spectra of hydrated samples recovered the original shape of areas structured at low laser fluence.
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    Fabrication and characterization of diffraction gratings in ophthalmic polymers by using UV direct laser interference patterning
    (Elsevier B.V., 2019-05) Sola, Daniel; Alamri, Sabri; Lasagni, Andrés F.; Artal, Pablo; Física
    The fabrication of diffractive elements in ophthalmic polymers to induce refractive index changes which may be applied for refractive correction is of great interest in the fields of Optics and Ophthalmology. In this work, polyhydroxyethyl-methacrylate and silicone hydrogel polymers used as soft contact lenses were structured with linear periodic patterns by means of Direct Laser Interference Patterning (DLIP). As the laser source, a Q-Switched laser system emitting 10 ns pulses at a wavelength of 266 nm was used to generate the periodic modulation on the surface of the polymer materials. The experiments were carried out employing a two-beam interference setup, studying the features of the laser processed areas as a function of both the laser fluence and the interference period. The topography of the structured areas was investigated using optical confocal microscopy. Compositional and structural modifications on the materials were studied by means of micro-Raman spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). Finally, periodic patterns were characterized through diffractive techniques under illumination of a continuous-wave 632.8 nm He-Ne laser to determine the diffractive properties of the DLIP periodic patterns and the refractive index change induced by the laser processing.
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    The role of thermal accumulation on the fabrication of diffraction gratings in ophthalmic PHEMA by ultrashort laser direct writing
    (MDPI, 2020-12-11) Sola Martínez, Daniel; Vázquez de Aldana, Javier R.; Artal Soriano, Pablo; Física
    The fabrication of diffraction gratings by ultrashort direct laser writing in poly-hydroxyethyl-methacrylate (PHEMA) polymers used as soft contact lenses is reported. Diffraction gratings were inscribed by focusing laser radiation 100 µm underneath the surface of the samples. Low- and high-repetition rate Ti:sapphire lasers with 120 fs pulsewidth working at 1 kHz and 80 MHz respectively were used to assess the role of thermal accumulation on microstructural and optical characteristics. Periodic patterns were produced for different values of repetition rate, pulse energy, laser wavelength, distance between tracks, and scanning speed. Compositional and structural modifications of the processed areas were studied by micro-Raman spectroscopy showing that under certain parameters, thermal accumulation may result in local densification. Far-field diffraction patterns were recorded for the produced gratings to assess the refractive index change induced in the processed areas.