Rapid aberration correction for diffractive X-ray optics by additive manufacturing

Abstract

Diffraction-limited hard X-ray optics are key components for high-resolution microscopy, in particular for upcoming synchrotron radiation sources with ultra-low emittance. Diffractive optics like multilayer Laue lenses (MLL) have the potential to reach unprecedented numerical apertures (NA) when used in a crossed geometry of two one-dimensionally focusing lenses. However, minuscule fluctuations in the manufacturing process and technical limitations for high NA X-ray lenses can prevent a diffraction-limited performance. We present a method to overcome these challenges with a tailor-made refractive phase plate. With at-wavelength metrology and a rapid prototyping approach we demonstrate aberration correction for a crossed pair of MLL, improving the Strehl ratio from 0.41(2) to 0.81(4) at a numerical aperture of 3.3 × 10−3. This highly adaptable aberration-correction scheme provides an important tool for diffraction-limited hard X-ray focusing.

Hard x-ray wavefront engineering for aberration correction and beam shaping

“…This work was recently published in Ref. 16. The optics were used in the Ptychographic Nano-Analytical Microscope (PtyNAMi) at beamline P06 of PETRA III at DESY in Hamburg, Germany.…”

“…More details about the focus can be found in Ref. 16. This aberration-correction scheme has a short implementation time.…”

“…A smoothed version of this phase error served as input for the production of a phase plate that was fabricated by 3D printing using a Nanoscribe Photonic Professional GT with the IP-S resist in dip-in lithography mode and a 25 × objective with NA = 0.8. 16 The phase plate was designed to compensate the phase error by refraction and was printed at the Paul Scherrer Institute. The thickness profile was determined for the chemical composition of the acrylic resin (C 14 H 18 O 7 ) with a cross-linked density ρ = 1.2 g cm −3 , leading to a Besides a high-resolution transmission image of the test object (left), the complex wavefield in the object plane is reconstructed (right).…”

“…This was illustrated by creating diffraction-limited hard X-ray nanobeams and correcting the aberrations of refractive 13,15 X-ray and Multilayer Laue Lenses (MLLs). 16 The method was analysed in detail, in particular in view of robustness against parameter variations. 19 It is well established by now with many applications 15 and will be illustrated using a recent example in Sec.…”

“…13,14 This phase error can then be compensated for by introducing an appropriate refractive phase plate made to measure. These phase plates can be fabricated by various techniques, e. g., laser ablation, 13 3D printing, 15,16 or focused ion beam milling and are used to correct various refractive and diffractive X-ray optics. Similar approaches to correcting the aberrations from reflective optics have been demonstrated using bimorph mirrors 17 and phase plates.…”