带宽对强光束非线性成像的抑制效应
Suppression of nonlinear imaging in high-power laser by pulse bandwidth
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摘要: 宽频带激光驱动器中光束的传输与常规的窄带系统有很大区别。数值分析了宽带激光的成像这一非线性传输现象，并与窄带激光的成像特性进行了比较，发现宽带激光的热像位置和窄带激光基本相同，但宽带激光的热像强度比窄带激光低很多，说明宽带激光能很好地抑制非线性成像的形成。此外，通过改变脉冲啁啾和脉冲宽度两种方式分别揭示了带宽对非线性成像和光束匀滑的影响，发现不同带宽情形下热像的位置基本相同，均处于共轭位置处；热像的光强和热像处光束的调制对比度随着啁啾值的增大而降低，随脉冲宽度的增大而增大。由于受到群速度色散效应的作用，带宽能够阻碍热像的形成，并提高光束的匀滑度。Abstract: The formation of hot image in a broadband laser system is numerically studied. It is found that in a broadband system the hot image is, though the same in location, well restrained by the bandwidth and has a peak intensity much smaller when compared to that in a narrowband system. In addition, the quantitative description for the influences of bandwidth on the hot image and on the uniformity of the beam is presented by modifying the chirp and temporal width of pulse. The results show that the intensity of the hot image and the corresponding contrast are inversely proportional to the chirp and proportional to the temporal width of the incident pulse, indicating that a bandwidth can suppress the formation of a hot image and improve the uniformity. The physical reasons for such a suppressing
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Key words:
- nonlinear optics /
- high-power laser /
- broadband laser /
- nonlinear imaging /
- propagation /
- suppression
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