Multifunctional single-crystal tellurium core multimaterial fiber via thermal drawing and laser recrystallization

In the field of multimaterial optical fibers, the demand for high-performance single-crystal core glass-clad multimaterial optical fibers is increasing. However, the applications of single-crystal fibers are restricted by the complex fabrication processes and the slow growth of single-crystal materials. Here, a two-step method is demonstrated to achieve single-crystal tellurium (Te) core fibers with high crystal quality over the length of the fiber. This method starts with the thermal drawing of a fiber preform into polycrystalline Te core multimaterial fibers (precursor fibers) that are long and mechanically stable. A 532-nm continuous laser is then employed to recrystallize the Te core in the precursor fiber into a single crystal state along the entire length of the fiber. Experimental studies of these single-crystal fibers demonstrate that the single-crystal Te core fibers possess high transmittance (>90% at 2–10 μm) and high thermoelectric performance (ZT values from 0.03 to 0.13 at 300 K temperature). They are superior to previous reports and our previous work. This method works for fabricating various single-crystal fibers and has important applications in the field of optical fibers, functional fibers, and their integrated devices.