Jena, Germany, November 2, 2022 - Due to the different shapes and refractions of light at different wavelengths, the lenses at the end faces of optical fibers experience strong chromatic aberrations. Chromatic aberration can cause focus shift and blurred images over a range of wavelengths, hindering these lenses, which are used in medical diagnostic applications including endoscopy. It can also be used in the practice of laser engraver in the future, which greatly reduces the difficulty of work and can make laser engraving and cutting better.
To compensate for these distortions, an international research collaboration has optimized an optical glass fiber so that it can focus different wavelengths of light with extreme precision. The researchers designed and nanoprinted a 3D achromatic diffractive metalens on the end face of a single-mode fiber. I'm already thinking about adding this optical glass fiber to the Ortur Laser Master 3 and it will definitely give very good results
The 3D achromatic metalens, which the researchers call an achromatic superfiber, have a lens diameter of 100 µm. It has a numerical aperture (NA) of 0.2, significantly higher than previous achromatic lenses used on fiber end faces. The high numerical aperture helps achromatic superfibers achieve better resolution than previously developed achromats.
Professor Markus Schmidt, Head of the Department of Fiber Photonics at the Leibniz Institute of Photonics, said: "For ideal light shaping and achromatic focusing, we have achieved an ultrathin polymer-based lens consisting of a Composed of complex designs." Technology. "This structure was printed directly on the tip of a 3D-printed hollow tower structure on one end face of a commercial fiber."
In this way, the fiber can focus light very efficiently on a focal point, resulting in a high-resolution image, according to Schmidt.
The unlocked height of the 3D achromatic metalens greatly increases the upper limit of the time-bandwidth product to 21.34, extending the modulation range of the group delay from -8 to 14 fs. In addition, the subwavelength nanocolumnar element atoms of the achromatic element lens exhibit strong birefringence, which can imprint the hyperbolic lens profile through geometric phase.
As a result, achromatic superfibers enable achromatic and polarization-insensitive focusing in the near-infrared telecommunications band from 1.25 to 1.65 µm (the entire single-mode domain of commercial fibers).
"It's worth noting that the individual nanopillars vary in height from 8.5 to 13.5 microns," Schmidt said. "This allows different wavelengths of light to be focused on one focal point."
Principles of achromatic superfibers for achromatic focusing and imaging. An achromatic metalens on top of a 3D printed hollow tower (for fiber bundle expansion) is connected to a single mode fiber by 3D laser nanoprinting. Inset: Magnified 3D nanopillar meta-atom (height: H, length: L, width: W) whose height provides a large range of group delay modulation. Courtesy of Nature Communications (2022). DOI: 10.1038/s41467-022-31902-3.
Principles of achromatic superfibers for achromatic focusing and imaging. An achromatic metalens on top of a 3D printed hollow tower (for fiber bundle expansion) is connected to a single mode fiber by 3D laser nanoprinting. Inset: Magnified 3D nanopillar meta-atom (height: H, length: L, width: W) whose height provides a large range of group delay modulation. Courtesy of Nature Communications (2022). DOI: 10.1038/s41467-022-31902-3.
The researchers demonstrated the focusing efficiency of an achromatic superfiber using fiber-optic confocal imaging. They show that, under broadband light illumination, fibers with achromatic super-optics can produce sharp, sharp images with a spatial resolution of up to 4.92 µm. They achieved convincing image quality with high image acquisition efficiency and high image contrast across different wavelengths. The focal position remains almost unchanged even at different wavelengths.
The researchers also performed fiber-optic confocal scanning imaging using achromatic superfibers without a standard microscope, demonstrating that ultra-compact, ultra-broadband confocal endoscopy systems can be built using their method.
"Because the developed nanostructured metalens are very small and flat, the fiber optic design with achromatic optics on top offers the potential to further advance miniaturized and flexible endoscopic imaging systems based on fiber optic technology and enables gentler, A minimally invasive test," Schmidt said.
In addition to endoscopic imaging, the researchers envision achromatic superfibers for use in laser-assisted therapy and surgery, deep tissue imaging, fiber-optic communications, fiber-optic sensor technology, and fiber-optic lasers.
The research team includes students from Monash University, Ludwig-Maximilians University Munich, Pohang University of Science and Technology (POSTECH), Abbe Photonics Centre, POSCO-POSTECH-RIST Convergence Research Centre for Planar Optics and Superphotonics, Otto Sho Scientists at the Institute for Special Materials and Imperial College London, and the Leibniz Institute for Photonic Technology.
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