Research Of Multilayer Blazed Grating With Ultra High Groove Density By Synchrotron Radiation Soft X-Ray

With the rapid development of synchrotron radiation in China,it is urgent to develop various optical devices.Gratings are important dispersive elements in UVU and soft X-ray bands.The quality of grating is closely interrelated to the light flow and energy resolution of the beamline.Multilayer blazed grating is a kind of layered grating based on blazed grating which multilayer film is coated.It is expected that Multilayer blazed grating can improve the plane grating monochromator.It theoretically can improve the energy coverage,improve the energy resolution and reduce the size of the monochromator.At-wavelength metrology is an important tool for the characterization of grating performance.There is no soft X-ray measurement beamline station at SSRF.In order to test the diffraction efficiency of multilayer blazed grating and study the diffraction performance of multilayer blazed grating,the following work has been carried out:(1)The scalar theory is only applicable to the case that the incident light is directly incident to the grating and incident light wave is far less than the grating constant.It is no longer applicable to the multilayer blazed grating in soft X-ray band.The classical differential theory is used to calculate the diffraction efficiency of the multilayer blazed grating.The differential algorithm is a vector algorithm,which is a strict solution of Maxwell’s equations in Fourier space.The diffraction characteristics of W/Si multilayer blazed grating are analyzed theoretically by calculation.Compared with conventional grating,the diffraction efficiency of multilayer blazed grating depends on the incident angle due to the effect of multilayer film.(2)Based on the existing beamline and scanning transmission X-ray microscopic experimental chamber,a miniaturized grating efficiency detection device is developed,which is convenient to install and disassemble.The device includes grating adjustment,detector adjustment,data acquisition and other systems.The diffraction efficiency of the multilayer blazed grating can be detected quickly.The Shadow software is used to trace the light beam,which proves the feasibility of the experimental scheme.(3)The multilayer blazed grating samples were tested.The results show that the diffraction efficiency of the multilayer blazed grating is consistent with the diffraction law of theoretical simulation.And the diffraction efficiency of +1 order is 0.52% under the incident light with the photon energy of 502 e V.In order to analyze the factors affecting the diffraction efficiency of the grating,the section and surface structure of the grating were measured by scanning transmission electron microscopy and atomic force microscope,and the influence of structural defects on the diffraction efficiency of the grating was analyzed.