HIGH RESOLUTION OPTICAL EXPERIMENTAL TECHNIQUE FOR COMPUTING PULSED LASER-INDUCED CAVITATION BUBBLE DYNAMICS IN A SINGLE SHOT

The experiments conducted in this study consisted of a series of plasma generated cavitation bubbles in water, obtained by focusing a 532-nm Q-switched Nd:YAG nanosecond-pulsed laser. For the purpose of detection of such cavitation bubbles, a novel direct light transmission technique is used, referred to as spatial transmission modulation (STM), consisting of a nearly collimated beam of light passing through the sample at the point where the cavitation bubble is formed. The presence of the cavitation bubble modifies the direct light transmission, which is detected with a photodiode located at the opposite end. This is observed as an electrical signal response with an oscilloscope. A 1-megapixel high-speed video camera simultaneously records the cavitation event. The video was taken in an orthogonal direction with respect to the STM optical axis and was triggered simultaneously with an oscilloscope using the electronic synchronization signal from the pulsed laser. Data from the highspeed video was used to show that a computational spatial energetic analysis from the continuous laser probe beam is a valid method to directly obtain the cavitation bubble evolution from a single shot pulse.