Role of light intensification by cracks in optical breakdown on surfaces.

The intensity distribution of an initially plane light wave incident on planar and conical surface cracks is calculated numerically by using a wave propagation computer code. The results show that light intensity enhancements caused by interference of internal reflections at the crack and the surface are very sensitive to the light polarization, the beam angle of incidence, and the crack geometry (e.g.

Index-of-refraction change in optically pumped solid-state laser materials.

Degenerate four-wave mixing measurements were made on several Nd(3+)-doped laser materials by resonantly pumping the Nd(3+) ions. The dominant contribution to the signal under these conditions is associated with the difference in polarizabilities of the Nd(3+) ions in the metastable state versus the ground state. Absolute measurements of the signal strengths imply a laser-induced polarizability change of the order of 0.