抽运激光在光靶中的局域及其对X射线激光特性的影响

新型X射线靶设计为:由SiO2和TiO2组成具有12个周期的一维光子晶体,在它的中间嵌入光靶材料层作为缺陷层,SiO2,TiO2和光靶层的光学厚度分别为λ4、λ4和λ2,λ为抽运激光波长.与普通平板光靶相比,当抽运光垂直照射到这种光靶时,靶层内部的光强将提高2个数量级,所以抽运激光的阈值强度将降低2个数量级,这有利于X射线激光的小型化.在同样的抽运激光照射下,X射线激光的强度将提高4个数量级,转换效率也将提高约4个数量级.由于平均电离度随抽运激光强度的提高而提高,所以采用这种光靶有利于使X射线激光向短波长推进. 关键词： X射线激光 光子晶体 光波局域

The designing of novel targets and their effects on X-ray lasers

The novel target used in X-ray lasers is designed as a one-dimensional photonic crystals (1D PCs) with 12 bilayers of SiO 2 and TiO 2, at the center of which a defect layer made of target material is embedded. The optical thickness of the target layer and each layer of the rest are a half and a quarter of the pumping laser wavelength, respectively. The pumping laser is, therefore, the localized mode of the 1D PCs. Compared with the common slab target, the pumping laser intensity in the target layer will be enhanced by about 2 orders. This is very important to the progress of X-ray lasers towards compactness, shorter wavelength and higher conversion efficiency. Gain coefficient will increase by a factor of 5, hence the target length in saturated XRL is reduced to one fifth. X-ray laser intensity will increase by about 4 orders, and so does the conversion efficiency. The average ionization state increases with pumping laser intensity, therefore, the wavelength of the X-ray laser will be shorter.