Cladding Glass Development for Semiconductor Core Optical Fibers

Glass-clad optical fibers comprising a crystalline semiconductor core have garnered considerable recent attention for their potential utility as novel waveguides for applications in nonlinear optics, sensing, power delivery, and biomedicine. To date, cladding compositions have relied on commercially-available expedients and have not been tailored for the specific semiconductor core nor the application. In this work, more-optimum silicate and nonoxide glass compositions are developed for unary (Si, Ge), binary (InSb, GaAs), and ternary (GaAlSb) semiconductor cores based on two main design criteria: (1) matching the thermal expansion coefficient between semiconductor core and glass cladding and (2) matching the viscosity-temperature dependences such that the cladding glass draws into fiber at a temperature slightly above the melting point of the semiconductor. While this latter requirement is critical to the molten core fabrication method, which offers a practical approach to long fiber lengths at acceptable manufacturing speeds (>m/s), these compositions are more broadly applicable to other semiconductor fiber processing methods. Preliminary experimental results on silicon core optical fiber are provided and show a marked diminution in oxygen content relative to analogous fibers drawn using a pure silica cladding.