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≈ 168 C. For T > 300 C, a phase explosion sets in, and R_max increases rapidly with E_L.