More are better, but the details matter: combinations of multiple Fresnel zone plates for improved resolution and efficiency in X-ray microscopy

Li, K.; Jacobsen, C.

doi:10.1107/S1600577518007208

Figure 2
The stacking of multiple thinner zone plates can lead to higher optical performance than can be obtained with a thicker single zone plate. On the left (a) is show the focusing efficiency (in terms of integrated energy fraction as a function of radius from the focal spot center) and, as an inset, the focused intensity profile for the three zone-plate design schemes and parameters outlined in Table 1

. This is for the case of zone plates separated by a very large distance of $[\Delta z]$ = 1000 µm relative to the focal length of f = 9074 µm for the first, upstream zone plate. The inset shows that the strategy of fixed diameter d gives a higher Rayleigh resolution (smaller radius for the first minimum of the intensity distribution) than the strategies of fixed outermost zone width dr_N or fixed zone number N. On the right (b) is shown the integrated energy fraction for a single t = 2000 nm-thick zone plate versus four t = 500 nm-thick zone plates separated by $[\Delta z]$ = 50 µm, and designed according to the fixed diameter d strategy. If multiple thinner zone plates can be aligned with sufficient accuracy, they can offer higher overall focusing efficiency (though in this case the separation between the zone plates is so small that they all have essentially the same numerical aperture, so there is no spatial resolution gain).

JOURNAL OF
SYNCHROTRON
RADIATION

ISSN: 1600-5775

Volume 25| Part 4| July 2018| Pages 1048-1059

https://doi.org/10.1107/S1600577518007208

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