Study On Diffraction Properties Of Quasi-random-dot-array Binary Gabor Zone Plates

As more and more widespread application of X-ray, its focusing and monochromatization has great significance. Refractive index of a variety of materials on the X-ray approximate 1, the average refractive focusing elements can no longer use, and preparation of conventional mirror with grazing incidence angle and multilayer film reflector is very difficult having problem of can not being widely used, zone plates which focus based on diffraction theory become a priority because they can be produced simply. Gabor zone plates a sort of zone plates have the properties of just one focus, better than Fresnel zone plates, but its implementation has been a problem. Binary Gabor zone plates and quasi-random-dot-array binary Gabor zone plates mentioned in the article can, respectively, achieve Gabor zone plates and simplify its achievement, so the application of Gabor zone plates in X-ray is laided a solid foundation.This paper aimed to carry out research on quasi-random-dot-array binary Gabor zone plates. First of all, diffraction intensity in the optical axis and focal plane and the imaging function of zone plates were analyzed basing on scalar diffraction theory so as to a better understanding of the diffraction properties of zone plates. For the new proposed zone plates, we simulated their diffraction properties, the results show that Gabor zone plates can be well achieved with quasi-random-dot-array binary Gabor zone plates. Quasi-random-dot-array binary Gabor zone plates are composed of a large number of a certain shaped base elements, the choice of shape and size for base elements is a very important issue, in the case of requiring zone plates with high diffraction efficiency, the shapes of base elements excludes all the choices except triangle, square and hexagonal shapes, we choose hexagonal shape as the primitive shape by comparing diffraction properties of three kinds of zone plates and taking into account the ease of preparation of zone plates. Then compared the diffraction properties of zone plates under different primitive size to determine the optimal size of the base elements. For practical applications, the incident light has a certain bandwidth and there is departure from the recording surface to focal plane, the paper found relations about these two factors and the influence on the size of focusing spot.Having produced quasi-random-dot-array binary Gabor zone plate for visible light with the base elements of hexagonal shape, the size of zone plate is 50 rings, its most inner radius is 700μm and the side length of hexagon is 5μm. Experiments with 650 nm incident light in order to research the diffraction properties of zone plates, after comparing experimental results and theoretical simulation, the correctness of the design and production of quasi-random-dot-array binary Gabor zone plate was confirmed. It is a good reference to design and produce zone plates for the X-ray.