Wavelength dependence of nanosecond and femtosecond optical breakdown in water: Theoretical analysis

This paper investigates the wavelength dependence of femtosecond and nanosecond optical breakdown in water with high wavelength resolution, temporally smooth laser pulses, and excellent focus quality. The experimental results are analyzed by comparing them to the predictions of a rate equation model considering photoionization based on the Keldysh theory, avalanche ionization based on the Drude model, as well as recombination and diffusion losses. Comparison of calculated breakdown thresholds I_rate(lambda) at different laser pulse durations tau with experimental I_th(lambda) results is done.