Wavefront Engineering and Polarization Dynamics in Biological Glass Fibers

Optical fibers are commonly used in different applications, such as data transmission and deep-tissue microscopy. Their small size and flexibility allow access to otherwise hard-to-reach areas. However, the fabrication process of these optical fibers, among other things, requires high temperatures and advanced processing methods, leading to substantial energy costs. A sustainable alternative can be found in nature. Specifically, sponges from the classes Hexactinellida and Demospongiae form endoskeletal structures comprising individual glass elements called spicules. In many cases, these spicules resemble microscopic fibers. Research has shown that long fiber-like spicules from Hexactinellid sponges exhibit a high-refractive-index core, surrounded by a lower refractive index cladding, thus forming an optical waveguide. Here, we demonstrate that sponge spicules from the Demospongiae class possess properties that can be utilized in fiber-based applications. In particular, we report the polarization dynamics and spatial wavefront shaping through needle-like spicules from the Tethya aurantium sponge. These biologically formed glass elements spark interest because they provide a sustainable and a cost-effective alternative to optical fibers’ fabrication.