Refractive Lenses by 2 Photon 3D Lithography
Refractive X-ray lenses are used in many synchrotron radiation applications, e.g. as objectives for full-field microscopy or for the creation of nanoscale beams for scanning techniques. The low refractive power of all lens materials introduces the need for very small radii of curvature, which complicates fabrication. Refractive lenses made from silicon, beryllium, aluminum or SU-8 have been reported, all with their individual advantages.
In a collaboration with DESY in Hamburg, Germany, we have developed additive manufacturing processes based on 2 photon 3D lithography for fabrication of X-ray optical components that offers high quality and greatly enhanced flexibility in optics design compared to established techniques. An example of a refractive lens made by 2 photon polymerization is shown in figure 1. The lens consists of three parabolic refractive surfaces, each with an apex radius of 3 µm, which results in a focal length of 240 mm at 8.2 keV. The beam caustic is calculated from the illumination function determined by a ptychographic scan and shows small sidelobe intensity. Propagation of the wavefront to the exit of the lens confirms aberrations to be significantly smaller than typically found e.g. in Be lenses.
- M. Lyubomirskiy, F. Koch, K.A. Abrashitova, V.O. Bessonov, N. Kokareva, A. Petrov, F. Seiboth, F. Wittwer, M. Kahnt, M. Seyrich, A.A. Fedyanin, C. David, and C.G. Schroer. Ptychographic characterisation of polymer compound refractive lenses manufactured by additive technology, Optics Express 27 (2019) p. 8639-8650