Abstract

Intensity-dependent changes in the refractive index of optical materials associated with the propagation of intense laser beams cause self-focusing and beam breakup and a resultant loss of focusable energy. For long amplifier chains, such as used in Nd-glass fusion lasers, beam degradation originates in many transmissive elements. These include the lasing medium, lenses, windows, polarizer substrates, Faraday rotators, and nonlinear crystals. The beam degradation is proportional to n₂/n(n − 1) for lenses, to n₂/n for laser rods, windows, and rotators oriented normal to the beam, and to n₂/n² for laser disks at Brewster’s angle, where n and n₂ are, respectively, the linear and nonlinear refractive indices. In all cases low n₂ values are desirable. Accurate data on n₂ is required for optimum staging of components in high-power laser systems.

© 1976 Optical Society of America