对高功率激光系统采用宽带激光消除菲涅耳衍射问题进行了研究，指出只有数百nm的宽带啁啾光脉冲才对近场衍射有一定的平滑作用，数nm的宽带啁啾光脉冲对近场衍射几乎没有平滑作用；同时，还对宽带啁啾光的B积分表征方式和最快增长频率问题进行了研究，并与原型装置上开展的窄带脉冲、宽带啁啾堆积脉冲的非线性实验结果进行了对比研究，指出以最大B积分或加权B积分反映非线性自聚焦更为准确。研究还表明，在数nm,ns情况下最快增长频率与窄带激光脉冲的差别不大。in high power laser system

High frequency spatial modulation induced by Fresnel diffraction of broadband nanosecond chirped laser pulse were studied. It shows that the hundreds-nm broadband pulse has some effects on Fresnel diffraction, while the tens-nm one has hardly any. Moreover, three B-integral expressions and the fast gain frequency of tens-nm broadband nanosecond chirped laser pulse were studied, and compared with the nonlinar experiments of narrowband pulse and chirped pulse stacking on Technical Intepration Lines facility. The results reveal that, the maximal B-integral or the weighted average B-integral can better reflect the nonlinear self-focusing phenomenon, and there are no distinct differences between the narrowband and the tens-nm broadband nanosecond laser pulses with respect to the fast gain frequency.