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We extend the third perturbation theory to study the polarization control behavior of the intermediate state absorption in Nd~(3+)ions. The results show that coherent interference can occur between the single-photon and three-photon excitation pathways, and depends on the central frequency of the femtosecond laser field. Moreover,single-photon and three-photon absorptions have different polarization control efficiencies, and the relative weight of three-photon absorption in the whole excitation processes can increase with increasing the laser intensity.Therefore, the enhancement or suppression of the intermediate state absorption can be realized and manipulated by properly designing the intensity and central frequency of the polarization modulated femtosecond laser field.This research can not only enrich theoretical research methods for the up-conversion luminescence manipulation of rare-earth ions, but also can provide a clear physical picture for understanding and controlling multi-photon absorption in a multiple energy level system.  相似文献   
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经过与γ射线探伤比较,决定采用超声波探伤进行球形薄壳件检测。超声波对缺陷的检出能力与缺陷的取向密切相关,为实现对多种取向缺陷的检出,超声束需由多个方向射入工件。为此,要求在检测过程中探头可以进行多种方式运动,要实现这一点,就必须建立适当的扫查装置。  相似文献   
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