Methods of investigating the role of absorbing microinclusions in damage to transparent dielectrics by laser radiation. I. Passive methods

Methods are considered for investigating absorbing inclusions of dimensions $d_i\lesssim3\times10^{-5}$ cm in transparent dielectrics. A quantitative criterion is proposed for discriminating between inclusions in respect of their size determined by investigation of light scattering. An ultramicroscopic method of measuring the sizedistribution function of inclusions of diameter $d_i\sim10^{-6}-3\times10^{-5}$ cm in the bulk of a transparent dielectric was proposed, tested experimentally, and appled to the industrial glasses K8 and TF5 and to liquating Na-7-B-23 glass. It is shown that all these glasses contain inhomogeneities of $d_i\sim 10^{-6} -10^{-5}$ cm size, with a concentration of $\lesssim10^{11}$ cm$^{-3}$, whereas the concentration of inhomogeneities of $d_i\lesssim3\times10^{-5}$ cm size does not exceed $3\times10^6$ cm$^{-3}$. Plots are made of the size-distribution functions of the inclusions in these glasses.