A New Technique for Nanoscale Imaging Using Lensless Technology
A new technique has been developed to examine tiny electronic and photonic components at the nanoscale, using lensless imaging. This method is especially useful for wavelengths shorter than ultraviolet, where traditional imaging methods are not as effective.
Known as ptychography, this form of lensless imaging involves scanning a laser-like beam across a sample and using a computer algorithm to create an image. However, ptychography struggles with samples that have regular, repeating patterns, as the scattered light remains unchanged during the scanning process, making it difficult for the algorithm to reconstruct an accurate image.
To tackle this challenge, researchers from JILA, including recent Ph.D. graduates Bin Wang and Nathan Brooks, developed a new method that utilizes short-wavelength light with a unique shape, such as a vortex or donut, to scan the repeating patterns. This results in more diverse diffraction patterns, enabling the researchers to reconstruct high-quality images of the sample. Their findings were recently published in the journal Optica and will also be featured in the Optica Magazine Optics and Photonics News in 2023.
This new imaging technique has significant implications for applications in nanoelectronics, photonics, and metamaterials. According to JILA Fellow Margaret Murnane, the ability to manipulate visible laser beams into different shapes has revolutionized visible super-resolution microscopy. Now, this new method allows for the same capabilities at shorter wavelengths.
To generate laser-like beams at shorter wavelengths, the JILA team used a process called high harmonic generation (HHG), which involves hitting atoms with an ultrafast laser pulse to produce extreme ultraviolet (EUV) light. By shaping the HHG beams into a vortex or donut shape, also known as an orbital angular momentum (OAM) beam, the researchers were able to alter the scattered light and obtain accurate images of the periodic sample.
Aside from its high-resolution capabilities, this new vortex-beam lensless imaging technique is also gentler on delicate samples compared to traditional scanning electron microscopy. This is crucial for imaging soft materials, plastics, and biological samples that are prone to damage.
Moreover, the vortex-beam method proved to be better at detecting defects in nanopatterns than scanning electron microscopy, which can damage fragile samples. This advancement opens up possibilities for imaging delicate live cells with high spatial resolution in the future, according to JILA Fellow Henry Kapteyn.
Overall, this new technique allows for high-resolution imaging of periodic structures without destroying them, making it valuable for scientists working with next-generation nanomaterials and devices. To learn more about this research, check out the publication titled "How 'Doughnut' Light Beams Unlock Microscopic Mysteries."