Effect of pulses from a high-power ytterbium fiber laser on a material with a nonuniform refractive index. I. Irradiation of yttrium oxide targets

The irradiation of Nd:Y$_2$O$_3$ targets with an absorption coefficient of 13–1.7 $\times$ 10$^3$ cm$^{-1}$ using laser pulses with a duration of 0.1–3.5 ms and peak power of 200–700 W at a power density of (0.2–1.3) $\times$ 10$^6$ W/cm$^2$ is studied. A relatively large spread of the delay times of laser plume, spike emission of the laser plume, cleavage of the front surface of the target, and greater ejection of substance from the crater in comparison with the effect of the CO$_2$-laser radiation with almost the same power are demonstrated. A numerical model of the effect of radiation on a target with a nonuniform refractive index is proposed to interpret the destruction of dielectric material (cleavage of the front surface) and the large spread of the delay times of the plume.