Advances in 3D-printed compound refractive lenses for x-ray focusing and wavefront engineering

Photopolymerization-based 3D printing is emerging as a promising approach for fabricating refractive x-ray optics, offering fast production, low cost, and high design flexibility. Unlike traditional manufacturing methods, 3D printing enables the fabrication of complex lens geometries with precise structural control, thereby opening up new possibilities for x-ray focusing and wavefront engineering in various synchrotron applications. In this work, we report recent progress in evaluating 3D-printed compound refractive lenses (CRLs) fabricated by two-photon polymerization. A systematic characterization strategy was implemented using at-wavelength metrology at Advanced Photon Source (APS) beamlines to provide direct feedback on lens performance. First, the refractive index of printed materials was precisely determined at the target X-ray energy, providing essential input for future lens design. Wavefront properties were then characterized using a coded mask wavefront sensing technique to extract residual phase error profiles and assess lens shape accuracy. Finally, the focusing performance of CRL stacks was evaluated, revealing direction-dependent aberrations and highlighting key factors that influence the optical quality of printed lenses.