Local thermionic mechanism for laser breakdown near the surface of a target

A phenomenological model is proposed for initiation of a laser plasma near the surface of an opaque target. The plasma formation criterion derived from the model agrees with the criterion established previously. It is shown that the plasma formation threshold depends on the characteristic defect size of the surface microrelief. A comparison of the critical defect sizes obtained from the proposed model shows that these agree with the experimental results with an error of less than ± 25%