  When illuminated by a laser, nano particles immersed in water can very
quickly and strongly heat up, leading to the nucleation of so called vapor
bubbles, which have huge application potential in e.g. solar light-harvesting,
catalysis, and for medical applications.Whilst the long-time behavior of such
bubbles has been well-studied, here, by employing ultra-high-speed imaging, we
reveal the nucleation and early life phase of these bubbles. After some delay
time after beginning of the illumination, a giant bubble explosively grows, up
to a maximal radius of 80 um, and collapses again within 200 us (bubble life
phase 1). The maximal bubble volume remarkably increases with decreasing laser
power P. To explain this behavior, we measure the delay time from the beginning
of the illumination up to nucleation,which drastically increases with
decreasing laser power, leading to less total dumped energy . This dumped
energy E shows a universal linear scaling relation. This finding supports that
the initial giant bubble is a pure vapor bubble. In contrast, the delay time
does depend on the gas concentration of the water, as gas pockets in the water
facilitate an earlier vapor bubble nucleation, which leads to smaller delay
times and lower bubble nucleation temperatures. After the collapse of the
initial giant bubbles, first much smaller oscillating bubbles form out of the
remaining gas nuclei (bubble life phase 2, up to typically 10 ms). Subsequently
the known vaporization dominated growth phase takes over and the bubble
stabilizes (life phase 3). In the final life phase 4 the bubble slowly grows by
gas expelling due to heating of the surrounding. Our findings on the explosive
growth and collapse during the early life phase of a vapor bubble have strong
bearings on possible applications of such bubbles, affecting their risk
assessment.
