克尔介质中超连续谱的产生与自聚焦的抑制

 从（3+1）维非线性薛定谔方程出发，理论上分析了超短脉冲频谱展宽与自聚焦的影响因素。分析得出：通过改变泵浦光的功率和光束口径，可以实现光谱的极大展宽并避免自聚焦成丝。数值模拟了小口径强泵浦光束在BK7玻璃中的传输过程并进行了实验验证。模拟结果显示在超连续谱产生的同时小尺度调制被完全抑制。实验结果表明：降低泵浦光功率，使光束不会因为全光束自聚焦而发生塌陷，同时还能控制除自聚焦外的其它非线性效应，进而改善近场光束质量。由于自相位调制是超短超强脉冲产生超连续谱的重要机制之一，需要维持传输过程中的泵浦光功率，由此最佳的入射光功率应选在全光束自聚焦功率阈值附近。

Supercontinuum generation and self-focusing in Kerr media

Supercontinuum generation and self-focusing effect of ultra-short pulse propagation in Kerr media were investigated according to (3+1) dimensions' nonlinear Schrdinger equation. Results indicate that spectral super-broadening without self-focus can be achieved by adjusting the pump power and the beam diameter. The process of a small diameter ultra-high power pump beam propagating in BK7 glass with or without small scale modulation was simulated. The experimental results indicate that the near-field beam quality improves when the pump power decreases. In this case, the pump beam doesn't collapse by whole beam self-focus and other nonlinear effects are restrained. In order to keep pump intensity in propagating, the best input power used for supercontinuum generation is near the whole beam