Er³  Yb³-codoped Al₂O₃crystal fibres for high-temperature sensing

Single-crystal sapphire fibres codoped with approximately equal amounts of rare-earth (RE) Er 3+ and Yb 3+ ions have been fabricated by the laser heated pedestal growth technique. The crystal fibres are then investigated for high-temperature sensing applications. Due to the unique transitions from the 4f electronic configuration in RE ions together with the high dopant concentrations used, strong upconverted emission in the visible has been observed. In particular, emissions in the green and red spectral regions have been exploited in an intensity-based sensing scheme for thermometric measurements up to ∼ 1320 and 1420 K respectively.