Hard X‐ray wavefront correction via refractive phase plates made by additive and subtractive fabrication techniques

Modern subtractive and additive manufacturing techniques present new avenues for X‐ray optics with complex shapes and patterns. Refractive phase plates acting as glasses for X‐ray optics have been fabricated, and spherical aberration in refractive X‐ray lenses made from beryllium has been successfully corrected. A diamond phase plate made by femtosecond laser ablation was found to improve the Strehl ratio of a lens stack with a numerical aperture (NA) of 0.88 × 10 −3 at 8.2 keV from 0.1 to 0.7. A polymer phase plate made by additive printing achieved an increase in the Strehl ratio of a lens stack at 35 keV with NA of 0.18 × 10 −3 from 0.15 to 0.89, demonstrating diffraction‐limited nanofocusing at high X‐ray energies.