Cover story: Wu GX, Zhu RZ, Lu YQ et al. Optical scanning endoscope via a single multimode optical fiber. Opto-Electron Sci 3, 230041 (2024).

Endoscopes are widely employed visual instruments in biomedicine, allowing in-depth, non-invasive, and rapid imaging of objects that cannot be directly accessed from the surface.  Diverse specialized endoscopes have greatly propelled the advancement of modern medicine. Among various endoscopic imaging techniques, optical fiber endoscopy is highly competitive due to its high flexibility, compact structure, excellent resolution, and resistance to electromagnetic interference. Regarding most imaging applications for relatively large structures, the well-developed optical fiber bundle endoscopes and single-mode fiber scanning endoscopes already meet demands effectively. Nevertheless, clinical medicine inherently requires continuous progress in the miniaturization of endoscopes to further alleviate the discomfort of patients, reduce lesions of tissues and expand application scenarios, such as implementing in neuroscience and ophthalmic surgery.

Over the past decade, multimode optical fiber scanning endoscopes have attracted widespread research interest due to their potential to significantly reduce the footprint and enhance imaging capabilities. Multimode optical fibers support the transmission of numerous guided modes, offering a large number of degrees of freedom for manipulating the optical field. By utilizing digitally programmable spatial light modulators, we can counteract the modal scrambling properties of multimode optical fibers and customize focal spots for all-optical scanning imaging. Given the ultrathin footprint and submicron imaging resolution, multimode optical fiber scanning endoscopes are certain to substantially drive the progress of diverse application fields spanning biology, medicine, and industry.