Fabrication of polycrystalline diamond refractive X-ray lens by femtosecond laser processing T. V. Kononenko 1,2 • V. G. Ralchenko 1,2 • E. E. Ashkinazi 1,2 • M. Polikarpov 3 • P. Ershov 3 • S. Kuznetsov 4 • V. Yunkin 4 • I. Snigireva 5 • V. I. Konov 1,2 Received: 7 September 2015 / Accepted: 2 October 2015 / Published online: 16 February 2016 Ó Springer-Verlag Berlin Heidelberg 2016 Abstract X-ray planar compound refractive lenses were fabricated from a polycrystalline diamond plate grown by chemical vapor deposition, by precise through cutting with femtosecond laser pulses. The lens geometry and the sur- face morphology were investigated with optical and scan- ning electron microscopy, while the material structure modification was analyzed by Raman spectroscopy. The results of the preliminary lens test at 9.25-keV X-rays are presented. 1 Introduction A direct mechanical treatment of diamond is difficult due to its extreme hardness and chemical inertness, while laser cutting is an attractive approach for diverse microma- chining of this material. During the last decade in diamond processing technology, a special attention has been giving to use of ultrashort laser pulses ( \ 10 ps), which ensures low ablation threshold (even in IR and visible spectral range), negligible thermal diffusion, and reduced thickness ( \ 50 nm) of graphitized layer [1] on the ablated diamond surface. The positive effect of applying of ultrashort pulses to precise diamond processing was verified with regard to high-aspect-ratio drilling and cutting [2], micromachining of diamond tool tips [3, 4], 3D surface profiling [5, 6], and submicrometer-scale surface structuring [7]. Among various technical applications of diamond, it is a promising material for fabrication of X-ray compound refractive lenses (CRLs, [8]), as diamond CRLs are able to withstand extreme heat and radiation loads while still providing effective focusing [9]. The first attempts to fabricate diamond lenses using either combination of electron-beam lithography and reactive-ion etching [10] or transfer molding technique [9, 11] were successful just partially. The desired focusing performance was not achieved due to low quality of the lenses produced. Although the diamond lenses manufactured later by the molding technique [12] showed an improved quality and uniformity, their thickness was *30 lm that is much less than the typical size of the X-ray beams available. Besides, thin diamond films grown on the silicon mold typically consist of nanocrystals (*50 nm) or small microcrystals (1–2 lm) that result in a reduced thermal conductivity in comparison with coarse-grade polycrystalline diamond (18–20 W/cmK) [13, 14] and also causing a noticeable scattering of X-rays. A high-precision laser cutting of single-crystal diamond plates was proposed recently [15] as a promising alterna- tive approach to lens manufacturing avoiding the men- tioned drawbacks. The main challenge in this case is keeping the verticality and smoothness of the cut walls, and the complexity increases with the plate thickness. As the first attempt, two compound lenses were fabricated in a 300-lm-thick single-crystal diamond plate of small size & T. V. Kononenko taras.kononenko@nsc.gpi.ru 1 General Physics Institute of Russian Academy of Sciences, Vavilov str. 38, Moscow, Russian Federation 119991 2 National Research Nuclear University ‘‘MEPhI’’, Kashirskoye shosse 31, Moscow, Russian Federation 115409 3 Functional Nanomaterials, Immanuel Kant Baltic Federal University, Nevskogo 14a, Kaliningrad, Russian Federation 236000 4 Institute of Microelectronics Technology RAS, Chernogolovka, Moscow region, Russian Federation 142432 5 European Synchrotron Radiation Facility, 71 av des Martyrs, 38043 Grenoble, France 123 Appl. Phys. A (2016) 122:152 DOI 10.1007/s00339-016-9683-9