The first ZnBr₂‐based upconversion glass fiber waveguide

Visible solid‐state lasers based on upconversion glass fiber waveguides are attractive because upconversion, the resonant conversion of near‐infrared (NIR) to visible light, permits high laser power in narrow bands and the fiber geometry guarantees a high exciting NIR radiation density along the entire absorption medium. The synthesis of the first upconversion fibers based on a heavier halide (ZnBr₂) is reported. A modified fiber preparation process that decreases the risk of attack by moisture is described and the losses along the fiber investigated.