部分相干同步辐射照射下光栅分数塔尔博特效应

Fractional Talbot Effect of Phase Gratings Illuminated by Partially Coherent Synchrotron Radiation

基于高斯谢尔光束的相干模式分解理论和波动光学,建立了部分相干同步辐射硬X射线光束通过光学器件的传播模型。模拟了微聚焦X射线光束照射下光栅的分数塔尔博特效应,得到了聚焦光束的光强分布和相干特性变化,并分析了散焦光束入射下的光栅自成像。然后通过模拟准直光束入射下的光栅塔尔博特效应,得到了不同传播距离处自成像条纹的变化情况,分析了影响光栅自成像条纹形状的因素。通过光栅衍射条纹测量同步辐射相干度,发现对矩形相位光栅来说,应该对衍射图样进行傅里叶分解,求出各级傅里叶系数随传播距离的变化曲线,从而得到入射光束相干特性。

Propagation model of hard X-ray beams from partially coherent synchrotron source through different optical elements is proposed based on the coherent mode decomposition of Gaussian-Schell model and wave-front propagation.The fractional Talbot effect of phase gratings illuminated by focused partially coherent synchrotron radiation is simulated.Both the focusing beam′s intensity distribution and the coherence properties are obtained.And the self-imaging of gratings illuminated by defocused beam is analyzed.The influences of different factors on the shape of Talbot images at different fractional Talbot distances are analyzed through the comparison of the self-imaging fringes in the diffraction pattern of gratings illuminated by collimated beam.The diffraction images of rectangular phase gratings are submitted to a Fourier transform procedure,yielding the Fourier coefficients of different orders as a function of propagation distance,and the information on the lateral coherence of the beam is obtained.