Theoretical study on how to improve the properties of x-ray lasers by designing targets - art. no. 043811

The target used in x-ray lasers (XRL) is designed as an one-dimensional pho tonic crystals (1D PC's) with 12 bilayers Of SiO2 and TiO2, at the center o f which a defect layer made of target material is embedded. The optical thi cknesses of the target layer and each layer of the others are one-half and one-quarter of the pumping laser wavelength, respectively, so that the pump ing laser is the localized mode of the 1D PC's. Compared with the common sl ab target, the pumping laser intensity in the target layer will be enhanced by about two orders. This is very important to the progress of x-ray laser s towards compactness, shorter wavelength, and higher-conversion efficiency . The gain coefficient will increase by a factor of five, hence, the target length in saturated XRL is reduced to one-fifth. X-ray laser intensity wil l increase by about four orders, and so does the conversion efficiency. The average ionization state increases with pumping laser intensity, therefore , x-ray lasers will shift towards shorter wavelength.