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.