ZrO2-SiO2 and Nb2O5-SiO2 mixture coatings as well as those of pure zirconia (ZrO2), niobia (Nb2O5), and silica (SiO2) deposited by ion-beam sputtering were investigated. Refractive-index dispersions, bandgaps, and volumetric fractions of materials in mixed coatings were analyzed from spectrophotometric data. Optical scattering, surface roughness, nanostructure, and optical resistance were also studied. Zirconia-silica mixtures experience the transition from crystalline to amorphous phase by increasing the content of SiO2. This also results in reduced surface roughness. All niobia and silica coatings and their mixtures were amorphous. The obtained laser-induced damage thresholds in the subpicosecond range also correlates with respect to the silica content in both zirconia- and niobia-silica mixtures.
A principal possibility to overcome fundamental (intrinsic) limit of pure optical materials laser light resistance is investigated by designing artificial materials with desired optical properties. We explore the suitability of high band-gap ultra-low refractive index material (n less than 1.38 at 550 nm) in the context of highly reflective coatings with enhanced optical resistance. The new generation all-silica (porous/nonporous) SiO2 thin film mirror with 99% reflectivity was prepared by glancing angle deposition (GLAD). Its damage performance was directly compared with state of the art hafnia/silica coating produced by Ion-Beam-Sputtering. Laser-Induced Damage Thresholds (LIDT) of both coatings were measured in nanosecond regime at 355 nm wavelength. Novel approach indicates the potential for coating to withstand laser fluence of at least 65 J/cm2 without reaching intrinsic threshold value. Reported concept can be expanded to virtually any design thus opening a new way of next generation thin film production well suited for high power laser applications.
A system for measurement of surface roughness based on total integrated scattering at 532 and 355 nm is built and demonstrated. Surfaces up to 25 mm × 25 mm are scanned in 6 min with a spatial resolution of 0.4 mm. Careful attention to reducing stray light and purging the measurement chamber with filtered air allow scattering resolution better than 10−5. Surface roughness measurements better than 1 nm RMS are demonstrated and confirmed by comparison measurements with an atomic-force microscope.
Nowadays, development of advanced devices or sensors often requires unique solutions that can be only solved with femtosecond laser micromachining. In this report we present the study of one of them: in order to create sensor for monitoring the health of metallic mould, conductive ceramic fiber ( Fig. 1-a) has be integrated into precut groove on the mould surface. Latter, the resistivity of the fiber has to be constantly monitored as it is directly linked to the wear level of the instrument [1]. Unfortunately, to get data about resistivity, electric wires should be attached to the ends of the ceramic fiber. This procedure is not straightforward: fiber has to be prepared in special way for sufficient and secure wire-to-fiber contact after the soldering. This preparation consists of creating micrometric notch in the fiber ( Fig. 1-b) for precise wire positioning and tight attachment.In this report we demonstrate that using femtosecond, high repetition rate Yb:KGW laser system it is possible to fulfil such task. Tested conductive ceramic samples had a diameter of ~250 μm [2]. We have used galvanometric scanners for beam deflection and long focusing f-theta lens together with various patterning algorithms in order to achieve required sizes of the notch. A simplified sketch of such processing is shown in Fig 1-c. For microfabrication of the notches we used following laser parameters: average power -2W at 1030 nm, pulse duration -300 fs and repetition rate -25 kHz. The cutting conditions for the good electric contact were selected and applied. In our experiments we achieved the steepness of the groove ~20°. We demonstrate that such microcutting procedure meets industrial requirements as it takes less than a second to process one ceramic fiber.Similar microcuting tests were also performed with picosecond laser pulses. We show that picosecond pulses can remelt conductive ceramics around processed region and amorphous slag appears that isolates ceramics from the conductive wire. Fig. 1 (a) Ceramic fibers and (b) the sketch of the notch made in fiber with targeted dimensions (units in micrometers).(c) Sketch of the notch cutting process at the both sides of the fiber with spiral algorithm.(d) Notch made in the ceramic fiber with patterning parameters.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.