Femtosecond-laser-induced nanocavitation in water: Implications for optical breakdown threshold and cell surgery

We determined the bubble radius R(max) for femtosecond optical breakdown in water at 347, 520, and 1040 nm with an unprecedented accuracy (+/- 10 nm). At threshold, R(max) was smaller than the diffraction-limited focus radius and ranged from 190 nm to 320 nm. The increase of R(max) with laser energy E(L) is slowest at 347 nm, providing optimum control of cell surgery. Experimental results agree with a model of bubble formation in heated and thermoelastically stretched liquids. Theory predicts a threshold temperature T(th)approximate to 168 degrees C. For T > 300 degrees C, a phase explosion sets in, and R(max) increases rapidly with E(L).