Diffraction modulation evolution from a knife-edge for small-scale self-focusing
Small-scale self-focusing is mostly caused by spatial diffraction modulation. It is the major factor for degradation of the laser pulse quality and the maximum output power. We investigate diffraction modulation evolution from a knife-edge for small-scale self-focusing through numerical calculation and experiment. We find that the effect of diffraction modulation weakens and the effect of small-scale self-focusing strengthens with the decrease of the truncation parameter. As the truncation parameter decreased continually, the effect of small-scale self-focusing strengthens sequentially,the laser begins split. In addition, the position of new growth for small-scale self-focusing is increasingly far away from the diffraction modulation peak and the diffraction fringes are broadened with the increment of the propagation distance. Our experimental results are in good agreement with an approximate theoretical analysis.
diffraction modulation knife-edge small-scale self-focusing nonlinear effect