Wavelength Dependence of Nanosecond and Femtosecond Optical Breakdown in Water: Theoretical Analysis

摘要

We investigated, to the best of our knowledge for the first time, the wavelength dependence of femtosecond and nanosecond optical breakdown in water with high wavelength resolution, temporally smooth laser pulses, and excellent focus quality [1]. In this presentation, we analyze the experimental results 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 [2]. Since the formation of brightly luminescent plasmas during nanosecond optical breakdown is associated with a temperature rise of several thousand K, we added another term considering thermal ionization obtaining the generic equation dρ/dt=(dρ/dt){sub}(photo)+η{sub}(casc)ρ-η{sub}(diff)ρ-η{sub}(rec)ρ{sup}2+η{sub}(therm).