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) approximately equal to 168 degrees C. For T>300 degrees C, a phase explosion sets in, and R_(max) increases rapidly with E_(L).