3D laser lithography technique in the fabrication of a coherent 2D kinoform X-ray lens

An analytical expression is obtained for the shape of a coherent kinoform X-ray lens surface, which is different from a parabola. A lens with a focal length of 1 m for monochromatic radiation with a photon energy of 12 keV is calculated. Two refractive lens materials—Rose’s alloy and silver—are selected. With a lens diameter of 200 μm, the diameter of the central diffraction maximum at the focus, calculated using the Huygens–Fresnel principle, is about 1 μm. The fraction of the light flux power incident on the lens in the central diffraction maximum of the focal spot is 14.6% for Rose’s alloy and 16.1% for silver. The capabilities of the femtosecond two-photon nanolithography developed at the Lebedev Physical Institute and Moscow Institute of Physics and Technology for producing efficient kinoform lenses for synchrotron radiation X-ray microscopy are demonstrated.