Fabrication of mid-infrared planar waveguides from compatible fluorozirconate glass pairs, via hot spin-casting

As there is a current demand for mid-infrared (IR) optical components an investigation was conducted to assess the possibility of producing planar, fluorozirconate glass waveguides. A series of ZBLANP [ZrF4–BaF2–LaF3–AlF3–NaF–PbF2] glasses was constructed by increasing substitution of BaF2 by PbF2. Glass samples were cast from the liquid for optical assessment purposes. The refractive index of these glasses was measured to an accuracy of ±0.3% using the minimum deviation technique. The refractive index was measured at 632.8 and 3390 nm. A pair of glasses was selected for production of a mid-IR planar waveguide to achieve the necessary numerical aperture (NA) for guiding at 3–5 μm. Using a hot spin-casting technique, combined with photolithography, a basic ridge guide of cross-section 50×50 μm was fabricated and the ends were polished and were examined using optical microscopy for roughness and shape. Optical guiding was demonstrated within the guide at 632.8 nm.