Topo‐Chemical Tailoring of Tellurium Quantum Dot Precipitation from Supercooled Polyphosphates for Broadband Optical Amplification

The generation of optically active precipitates and quantum dots in glasses suitable for fiber application is a challenging task, in particular, for glasses which exhibit superbroad near‐infrared (NIR) photoemission. The latter can be achieved through dopants of heavy metal and post‐transition elements, but their stabilization in the desired chemical state requires unconventional approaches of synthesis. Here, atomic clusters of tellurium and metallic tellurium quantum dots in polyphosphate matrices are considered. Starting from the understanding of glass structure where the length and the degree of crosslinking of phosphate chains can be adjusted through composition, generation and stabilization of tellurium precipitates with ultra‐broadband infrared photoluminescence are demonstrated. Increased network crosslinking and, hence, increased molecular rigidity of the host enables finely distributed precipitates of optically active tellurium species. This demonstrates a generalist approach as to how the precipitation of metallic nanostructures can be tailored through network topology. In the present situation, the size of metallic tellurium inclusions can be limited to sub‐nanometric scale, enabling a luminescence bandwidth of about 260 nm across the telecommunication bands, and an emission lifetime of several tens of μs. In a demonstration experiment, it is shown that this strategy of structural control can be transferred to application in optical fiber.