Effect of Optical Fiber Output Surface on Laser Induced Shock Wave and Its Application

Abstract

A high-pressure pulse is produced from an optical fiber output surface under the application of a pulsed laser. We found that enhancement of the absorption of laser energy due to the generation and growth of plasma takes place at the output surface, if the surface is intentionally roughened. The effect of roughness causes the pressure enhancement of the generated shock wave in water. We also found high pressure shock wave propagation in water from the fiber on which the output surface was roughened and rounded intentionally. These measures further enhance the shock wave generation. These enhancement phenomena due to the roughness and the round shape can be used as a controllable pressure pulse source for microsurgery in medicine. They have been observed by means of pulsed laser shadowgraphy. The shock wave propagation characteristics are found to depend upon various parameters such as the fiber diameter, the fiber material, the surface roughness, the surrounding medium, and the laser energy. As an example of the application of shock wave propagation, an experiment in cutting gelatin by means of the shock wave was carried out. The cross section of gelatin is strongly dependent on the pulse duration time width of the laser. When the duration time is 1.7 µs, the gelatin was cut most deeply.