Image of the Week: Light Thread A microscope image of an optical step-index fiber that has been processed with a CO2 laser. The laser focus rotates around the fiber and writes a track into the surface. The fiber feeding generates the helical structure. Light that is guided in the fiber cladding disrupts the total internal reflection to the surrounding medium. [2025 #OPNPhotoContest Honorable Mention] Steffen Böhme, Fraunhofer IOF, Jena, Germany *Link in Bio