Figure 1

Schematic of the experimental setup for imaging experiments: CL, collimation lenses used to expand the beam waist from 1 to 25 mm; HWP, half wave plate used to adjust the polarization angle of the light exiting the laser; PBS, polarizing beam splitter used in combination with the half wave plate to adjust the downstream laser energy, $5\times 5$, phase grating responsible for generating the $5\times 5$ grid pattern of laser beams; FL, 125-mm focal length lens used to focus the laser into the center of the sphere.Reuse & Permissions

Figure 2

Time-resolved images of a light emission event with a ($5\times 5$)-mm field of view. This experiment was carried out at an ambient pressure of 30 MPa with a peak acoustic pressure of 35 MPa. The laser was fired 1 $\mu$s before the peak negative phase of the acoustics to nucleate the cloud and the first image began 20 ns before the peak positive phase of the acoustics. The image series spanned 75 ns with each frame having an exposure time of 5 ns with another 5 ns between frames. Frames 1–4 progress from left to right on the top row of the image series, followed in a similar fashion by frames 5–8 on the bottom row.Reuse & Permissions

Figure 3

Photomultiplier tube signal of a single event showing multiple peaks.Reuse & Permissions

Figure 4

Overlay plots of the evolution of events from 36 eight-cycle image sequences. This experiment was carried out at an ambient pressure of 17 MPa with a peak acoustic pressure of 22 MPa. Exposure times were set to 1 $\mu$s with each image starting 500 ns before the peak positive pressure of each listed cycle, with cycles lasting 38 $\mu$s. The laser was fired once at cycle 0, 1 $\mu$s before the peak negative phase of the acoustics. These images were made by stacking frames from 36 sets of images of events over 8 acoustic cycles on top of one another. This involved going pixel by pixel through each of the 36 frames per cycle and comparing the brightness of that pixel in each frame and then assigning the new pixel the brightest value observed in the 36 frames. This ensured that each image would show peak brightness as well as the spatial distribution of SL events from cycle to cycle without diminishing events that were not centrally located as simple averaging would have.Reuse & Permissions

Figure 5

Backlit image of a light emission event with a ($4\times 3$)-mm field of view. The image series spanned 435 ns with frame exposure times of 50 and 5 ns between each frame. Frames 1–3 show the final stages of the cloud collapse, frame 4 shows the light emission event, and frames 5–8 show the development of a shock wave from the collapse.Reuse & Permissions

Figure 6

Radius vs time plot showing the cloud, sonoluminescence (SL), and shock radius for a typical event. The uncertainties in the values presented are $\pm$10 $\mu$m.Reuse & Permissions

Figure 7

Integrated PMT signal vs pressure data from five experiments at each pressure from 6.9 to 27.6 MPa. Each data point represents the integration of the PMT signal from the nucleation of the first bubble cloud to the last observable event in the run.Reuse & Permissions