Optical fiber integrated functional elements fabricated by two-photon polymerization

Optical fibers are one of the most extensively used and powerful devices in the fields of medicine, sensing, power delivery and communication due to their ultra-compact size and low optical loss. Over the last years, researchers have been trying to further enhance the capabilities of this technology by integrating functional structures onto the fibers. This has enabled various applications in micro-optics, such as sensing, imaging and optical trapping. However, the non-planar surface of the optical fibers as well as the small and delicate area of their tip makes the use of standard micro- and nanofabrication techniques extremely challenging. On the contrary, two-photon polymerization (2PP), owing to its high versatility, holds great promise for fabricating advanced functional elements on fibers. Here, we review recent progress on optical fiber integrated functional devices enabled by 2PP.