Observation of water-shock-wave propagation emanated from the roughened optical fiber end surface by the pulse laser energy input

Abstract

Pressure enhancement of the generated shock waves in water has been found, when pulse laser energy is transmiued through an optical fiber whose end surface is intentionally roughened. More effective high-pressure shock generation can be possible by the aluminum coating on the roughened fiber surface. In case of the moderate laser energy of about 50 mJ input to the fiber, it is found that the phenomena are dependent on (1) the roughness, (2) the fiber diameter, and (3) the ambient medium. Shock wave generation can be detected successively by the laser input, but found to degrade down. Cavitation bubbles have also been observed after each shot. When the fiber end is in air, an intense and long-strechted flash can be observed. We have observed the phenomena by the pulse laser shadowgraphy.