Research of Optical Breakdown Induced by Nanosecond Laser in Water and Gold Nanosphere Solutions

Optical breakdown induced by nanosecond laser in deionized water and gold nanosphere solutions with 24 nm diameter is investigated based on bright plasma imaging and light scattering detection technique. More than one laser-induced breakdown regions are generated along the direction of beam propagation as a function of incident laser energy, which is denoted as multi-point breakdown. And the stretching of bright plasma is asymmetry along optical axial direction, especially in low concentration of gold nanoshere solution. Weak breakdown occurs only when laser energy is low, and strong breakdown occurs only when laser pulses energy exceeds the given energy. Low concentration gold nanosphere can decrease the minimum energy which could induce optical breakdown by laser pulses. Increasing concentration of gold nanosphere can lead to the larger energy threshold of optical breakdown. In addition, it's easier to get submicron size bubble in gold nanosphere solutions than in deionized water, and the size of bubble induced in gold nanosphere solutions are more stable.