Propagation of a high‐intensity laser pulse with small‐scale intensity modulation

For laser beams of large aperture with power far above the critical power for self‐focusing, nonlinear propagation instabilities lead to the growth of small‐scale variations in intensity and phase. We report measurements of the growth rate for interference fringes in unpumped ED‐2 laser glass as a function of fringe spacing and intensity. Calculations based on the simplest form of linearized small‐scale instability theory agree approximately with the measured rates, and a more complete linearized treatment predicts the growth rates within experimental error.