  We report on the photodamage mechanism underlying the highly nonlinear
interaction of femtosecond pulses at 1030 nm with the central nervous system
tissue in living zebrafish (Danio rerio). Our study identifies two different
cavitation regimes. The damage is confined and well-controlled at low
repetition rates due to plasma-based ablation and sudden local temperature
rise. At high repetition rates, the damage becomes collateral due to
plasma-mediated photochemistry and is not influenced by the thermal
accumulation of consecutive laser pulses. Furthermore, we investigate and
quantify the role of fluorescence labels with linear and nonlinear absorption
pathways in optical breakdown. To verify our findings, we examined cell death
and cellular responses to tissue damage, including the recruitment of
fibroblasts and immune cells at different time points post-irradiation. These
findings contribute to advancing the emerging nonlinear optical microscopy
techniques and provide a strategy for inducing deep-tissue, precise, and
localized injuries using near-infrared femtosecond laser pulses
