Ultrafast laser welding of ceramics.

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.

Evaluation of mechanical behavior of soft tissue by means of random laser emission.

We demonstrate the use of random laser emission for mechanical testing of bovine pericardium. An apparatus designed for tensile tests of soft and thin materials, incorporating optical and mechanical devices, allows for obtaining the mechanical behavior of the tissue samples. Using both, digital image correlation (DIC) and random laser emission analysis, the apparatus provides information regarding the response of the bovine pericardium under different stress levels. Our results show that changes in the spectral features of the random laser correlate well to the mechanical response obtained with conventional uniaxial tensile analysis coupled with DIC. Furthermore, parameters such as the shear and Young moduli are consistent with values reported previously and obtained with other techniques. Changes at the microstructural level of the tissue may thus be evaluated through spectral analysis of the random laser emission from biological samples.