Ptychography, a powerful type of lensless imaging, uses a scanning beam to gather scattered light for image restoration, facing obstacles with routine samples.To study nanoscale patterns in tiny electronic or photonic elements, a new method based on lensless imaging enables for near-perfect high-resolution microscopy. And if millions of atoms all give off the EUV light synchronously, the waves produce an intense laser-like EUV beam.To image repeating patterns, the JILA scientists needed to discover a method to change the HHG beam so that the spread light altered as the EUV beam was scanned over the sample. The scientists coaxed the HHG beams to change from a disk into a vortex or donut shape, which is called an orbital angular momentum (OAM) beam, to attain this impact.
Scatter pattern produced by doughnut-shaped beams of light bouncing off of an object with a regularly duplicating structure. Credit: Wang, et al., 2023, “Optica” To study nanoscale patterns in small electronic or photonic elements, a brand-new method based on lensless imaging enables near-perfect high-resolution microscopy. Ptychography, a powerful type of lensless imaging, utilizes a scanning beam to gather scattered light for image reconstruction, dealing with difficulties with routine samples.To study nanoscale patterns in small electronic or photonic parts, a new method based upon lensless imaging permits near-perfect high-resolution microscopy. This is specifically essential at wavelengths much shorter than ultraviolet, which can image with higher spatial resolution than visible light but where image-forming optics are imperfect.The most powerful type of lensless imaging is called ptychography, which works by scanning a laser-like beam across a sample, collecting the spread light, and after that utilizing a computer system algorithm to reconstruct an image of the sample.While ptychography can picture many nanostructures, this unique microscopic lense has trouble examining samples with extremely regular, repeating patterns. This is since the spread light does not change as a routine sample is scanned, so the computer system algorithm gets puzzled and can not reconstruct an excellent image.Taking on this difficulty, recently graduated Ph.D. researchers Bin Wang and Nathan Brooks, working with JILA Fellows Margaret Murnane and Henry Kapteyn, established a novel approach that uses short-wavelength light with a special vortex or donut shape to scan these duplicating surfaces, leading to more diverse diffraction patterns. This permitted the researchers to catch high-fidelity image restorations utilizing this brand-new approach, which they recently published in the journal Optica. This outcome will also be highlighted in the Optica Magazine Optics and Photonics News in the annual highlights of Optics in 2023. This new imaging technique is particularly impactful for applications in metamaterials, photonics, and nanoelectronics. “The ability to structure (or change the shape of) visible laser beams into donut and other shapes has actually reinvented noticeable super-resolution microscopy,” explained Murnane. “It is very exciting to now have a path forward for bringing these powerful capabilities to shorter wavelengths.” Sculpting Vortex-Shaped High Harmonic BeamsTo create laser-like beams at brief wavelengths in a tabletop scale setup, the JILA team used a procedure called high harmonic generation (HHG). HHG happens when an ultrafast laser pulse hits an atom, plucking an electron away and then driving it back to its parent atom to recombine. Upon contact, the atoms convert their electrons kinetic energy into extreme ultraviolet (EUV) light. And if countless atoms all give off the EUV light synchronously, the waves produce a brilliant laser-like EUV beam.To image duplicating patterns, the JILA researchers required to discover a way to change the HHG beam so that the spread light changed as the EUV beam was scanned over the sample. The researchers coaxed the HHG beams to transform from a disk into a vortex or donut shape, which is called an orbital angular momentum (OAM) beam, to achieve this result. This various shape would be important to allow lensless imaging of regular samples.When the scientists brightened their microscopic lense with vortex-shaped HHG beams (see accompanying image), more elaborate scatter patterns were produced, which altered as the sample was scanned. These variations encoded information about the samples repeating motifs and enabled the algorithm to extract a precise image.Beyond this interesting outcome, this new vortex-beam lensless imaging also produced less damage to the fragile sample than that of a scanning electron microscope. As lots of soft products, plastic, and biological samples are vulnerable, having a gentle and accurate method to image them is key.Additionally, vortex-beam lensless imaging was better at finding problems in the nanopattern than scanning electron microscopy, which tends to melt delicate samples.Patterns, Patterns, Everywhere– and Now We Can See them BetterFor researchers making patterned products for next-generation nano, energy, photonic, and quantum devices, this advance enables high-resolution imaging of highly regular structures, without destroying them. As Kapteyn elaborated: “In the future, this may also make it possible to image fragile live cells at high spatial resolution.” For more on this research, see How “Doughnut” Light Beams Unlock Microscopic Mysteries.Reference: “High-fidelity ptychographic imaging of extremely regular structures enabled by vortex high harmonic beams” by Michael Tanksalvala, Henry C. Kapteyn, Bin Wang, Peter Johnsen, Yuka Esashi, Iona Binnie, Margaret M. Murnane, Nicholas W. Jenkins and Nathan J. Brooks, 19 September 2023, Optica.DOI: doi:10.1364/ OPTICA.498619.