SIMPLE METHOD FOR LASER CHIRP DIAGNOSIS - APPLICATION TO THE MEASUREMENT OF THE YLF NONLINEAR KERR COEFFICIENT

We present a simple method for diagnosis, visualizing and measuring of the frequency chirp of a laser pulse. This method relies on the use o f a streak-camera to temporally resolve a spatial interference pattern produced by the pulse. Analysis of the streak-camera data gives direc tly the functional form of the chirp including its sign and its higher order nonlinear components which can provide information on the physi cal process causing it, namely the self-phase modulation that the puls e undergoes in the laser medium in the course of its amplification. By studying the temporal profile of the laser coherence we have been abl e to measure the gain bandwidth and the third-order nonlinear coeffici ent for the YLF:Nd+3 laser medium: X'3' = ( 1.6 +/- 0.6) X 10(-19)m(2) W(-1).