Optical image formation with a Fresnel zone plate using vacuum-ultraviolet radiation*

A self-supporting Fresnel zone plate with empty transparent zones has been used to focus vacuum-ultraviolet (vuv) radiation with wavelengths as short as 565 Å. The radiation was produced by two broad-band sources, (i) the molecular continuum of a helium gas-discharge lamp, which extends from 600 to 1100 Å with a broad peak at 810 Å, and (ii) the synchrotron continuum of an electron storage ring filtered by a Sn filter, which extends from 520 to 750 Å with a broad peak at 565 Å. The zone plate was used as a simple converging lens to form an optical image of an object mesh on a sodium salicylate film, where it was photographically recorded. Magnifications of 20× and linear resolutions within an order of magnitude of the theoretical resolution limit of the zone plate were obtained. Applications of this device as a vuv microscope are discussed.