While printing lenses is nothing new, the field is continually providing in-depth nanoscale applications to optical tools. Researchers at the Max Planck Institute for Intelligent Systems in Stuttgart are taking this to the next level with their new line of polymer lenses for x-ray microscopes. Thanks to the in-depth resolution of modern additive manufacturing, they’ve given these lenses nano-scale features.
X-ray microscopy is a means of studying microscopic features in all sorts of equipment. It can be crucial in, for example, studying defect in microchips and CPU’s. It’s the best means of getting a good grasp of the structural faults of crucial devices. However, XRM requires very high power, intricate lenses so the researchers have been workshopping a method to produce them far cheaper. Due to their nanoscale geometries, they can be expensive, costing upwards of thousands of Euros. Their new production method provides a far more economical alternative.
The researchers used femtosecond two-photon 3D nanoprinting to fabricate this new diffractive X-ray optic. Aside from being being cheap, the method is also very quick, producing each lens in under a minute with extremely favorable X-ray optical properties. It can also employ multiple stacks of lenses for processing simultaneously.
Producing X-Ray Microscope Lenses
“We used a femtosecond pulsed infrared (IR) laser, and a photoresist that can polymerize by absorbing multiple infrared photons simultaneously to write structures smaller than the wavelength of light“, said Umut T. Sanli, Ph.D. student from the Micro/Nano Optics group of the Modern Magnetic Systems Department. “This way, we achieved an extremely challenging X-ray lens geometry with nanometer-size features and very high focusing efficiencies.“. The 3D‐printed kinoforms resulting from direct soft X‐ray imaging and ptychography demonstrated superior performance, displaying efficiencies of up to 20%.
It was also important to pick the materials with caution because of how much radiation damage the lenses incur. The team used two-photon polymerisation to create the lenses out of plastic. They considered a whole bunch of different materials (including beryllium and diamond). The polymer lenses are safe to manufacture and once manufacturers optimise them, the fabrication is straightforward.
The researchers applied the method for more efficiency by combining several of the lenses in series. By integrating various optics, they effectively control and manipulate the X-ray wavefront. With several lenses and other wavefront shaping elements positioned one after the other, they optimise these integrated X-ray optics for even the very hard X-ray energy range.
The researchers have filed a patent for the new method. The full paper detailing their research is available here.
Images courtesy of the Planck Institute.