Welding of ceramics is a key missing component in modern manufacturing. Current methods cannot join ceramics in proximity to temperature-sensitive materials like polymers and electronic components. We introduce an ultrafast pulsed laser welding approach that relies on focusing light on interfaces to ensure an optical interaction volume in ceramics to stimulate nonlinear absorption processes, causing localized melting rather than ablation. The key is the interplay between linear and nonlinear optical properties and laser energy–material coupling. The welded ceramic assemblies hold high vacuum and have shear strengths comparable to metal-to-ceramic diffusion bonds. Laser welding can make ceramics integral components in devices for harsh environments as well as in optoelectronic and/or electronic packages needing visible-radio frequency transparency.

Traditionally accepted design paradigms dictate that only optically isotropic (cubic) crystal structures with high equilibrium solubilities of optically active ions are suitable for polycrystalline laser gain media. The restriction of symmetry is due to light scattering caused by randomly oriented anisotropic crystals, whereas the solubility problem arises from the need for sufficient active dopants in the media. These criteria limit material choices and exclude materials that have superior thermo-mechanical properties than state-of-the-art laser materials. Alumina (Al2O3) is an ideal example; it has a higher fracture strength and thermal conductivity than today’s gain materials, which could lead to revolutionary laser performance. However, alumina has uniaxial optical proprieties, and the solubility of rare earths (REs) is two-to-three orders of magnitude lower than the dopant concentrations in typical RE-based gain media. We present new strategies to overcome these obstacles and demonstrate gain in a RE-doped alumina (Nd:Al2O3) for the first time. The key insight relies on tailoring the crystallite size to other important length scales—the wavelength of light and interatomic dopant distances, which minimize optical losses and allow successful Nd doping. The result is a laser gain medium with a thermo-mechanical figure of merit of Rs~19,500 Wm−1 a 24-fold and 19,500-fold improvements over the high-energy-laser leaders Nd:YAG (Rs~800 Wm−1) and Nd:Glass (Rs~1 Wm−1), respectively. Moreover, the emission bandwidth of Nd:Al2O3 is broad: ~13 THz. The successful demonstration of gain and high bandwidth in a medium with superior Rs can lead to the development of lasers with previously unobtainable high-peak powers, short pulses, tunability, and high-duty cycles.

This report presents a study of shock wave and cavitation bubble dynamics induced by nanosecond laser pulses in pressurized water. Three methods were used to obtain data from the irradiated sample: (1) pump-probe laser flash shadowgraphy, (2) pressure wave sensing by means of a fiber optic interferometer hydrophone, and (3) a novel technique based on the modulation of spatial transmittance by the cavitation bubble. The medium used in these experiments was distilled water in a chamber under different pressure conditions which included values found in human intraocular liquid. It could be shown that while external pressure does not affect either the shock wave propagation or the initial bubble growth rate, it does affect the first collapse time of the bubble and its maximum diameter.Keywords: bubble; shock wave; microsurgery; pressure; intraocular.Zusammenfassung : Die vorliegende Arbeit untersucht die Dynamik von Schockwellen und Kavitationsblasen, die mittels Nanosekunden-Laserpulsen in unter Druck gesetztem Wasser erzeugt wurden. Dabei wurden drei unterschiedliche Methoden verwendet: (1) Laserflash-Verfahren, (2) Druckwellenmessung mittels faseroptischem Interferometer und (3) eine neuartige Technik basierend auf der Modulation der r ä umlichen Transmission durch die Kavitationsblase. Die Untersuchungen wurden an destilliertem Wasser unter unterschiedlichen Dr ü cken -u.a. auch physiologische Werte, wie sie intraokular vorkommen -vorgenommen, die mittels einer speziellen Druckkammer erzeugt wurden. Es konnte gezeigt werden, dass weder die Ausbreitung der Schockwelle noch das anf ä ngliche Blasenwachstum durch den ä u ß eren Druck beeinflusst wird, die Kollapszeit der Blase und ihr maximaler Durchmesser jedoch sehr wohl.Schl ü sselw ö rter: Blase; Schockwelle; Mikrochirurgie; Druck; intraokular.