Development of a novel light source for speckle-free flash photography

Temporally high-resolution short-time photography in the range of 100 ps exposure time is possible by stroboscopic illumination with ultra-short laser pulses, but the coherent emission often leads to image artifacts such as laser speckle, which disturb the photographic images. In a future project, therefore, a novel light source will be developed that is suitable for speckle-free short-term photography. This source will be used to visualize cavitation bubble dynamics in free liquid and during the production of nanoparticles.

The production of high-purity nanoparticles by laser ablation in a liquid environment is a growing research and industrial sector, as nanoparticles are increasingly entering the biomedical field, but their high-purity production in large numbers is still problematic. The exact process of nanoparticle production during laser ablation of the target structure is not yet fully understood, especially the role of cavitation bubble dynamics including the distinct bubble collapse is largely unclear.

Within the scope of current research activities a special detection technique has been developed, which allows the study of the dynamics of a laser-induced cavitation bubble in a single shot procedure. By back reflection of a probe laser at the bubble walls and its interferometric interference, this method achieves a previously unattained temporal and spatial resolution in the range of 70 nm and 160 ps. This method, including the speckle-free short-term photography to be developed, will be applied to better understand the laser-induced production of nanoparticles.