As synchrotron light sources evolve toward the diffraction limit, the primary bottleneck in hard X-ray microscopy has shifted from source brilliance to wavefront transport and preservation. Nanometer-scale surface figure deviations manifest as irreversible phase aberrations, making the deterministic manufacturing of diffraction-limited nanofocusing optics the critical limiting factor.
In a new paper published in Light: Advanced Manufacturing , a team of scientists from the National Synchrotron Light Source II (NSLS-II) at Brookhaven National Laboratory (BNL) have established the first fully in-house, end-to-end pipeline in the United States that links atomic-scale fabrication and precision ex situ metrology to in situ X-ray beam validation.
The manufacturing pipeline begins with deterministic Ion Beam Figuring (IBF) and rhodium coating of elliptical Kirkpatrick—Baez (KB) mirrors. Guided by rigorous metrology combining stitching interferometry and nano-accuracy surface profiling, the team drove residual height errors down to approximately 0.4 nm root-mean-square. Utilizing these precise surface maps, they employed partially coherent wave-optics simulations to predict a focal spot of 77 by 36 nanometers. This forward prediction was rigorously validated in situ at the beamline using ptychography, which reconstructed a highly consistent 70.5 by 33.1 nanometer focal spot. To provide an independent, application-level benchmark, X-ray fluorescence imaging of a Siemens star test pattern successfully resolved features down to 30 nanometers.
To prove the pipeline's closed-loop consistency, the team numerically back-propagated the complex probe from the focal plane to the mirror pupils, demonstrating that the derived at-wavefront surface errors quantitatively mirrored the ex situ metrology residuals. The researchers summarize the significance of closing this loop:
“Ultimately, atomic-scale fabrication is necessary but not sufficient. The system-level bottleneck is the ability to carry a measured surface state through realistic wave-optics transport and recover it again from at-wavefront measurements in the real application configuration. By establishing this pipeline, we have created an integrated manufacturing framework that enables the deterministic delivery of atomic-scale optics for next-generation light sources.”
Light: Advanced Manufacturing
In-house pipeline from atomic-scale fabrication to at-wavefront validation of synchrotron X-ray nanofocusing mirrors