Fabrication of a Miniaturized Thin-Film Temperature Sensor on a Sapphire Fiber Tip

We report a miniature thin-film-based high-temperature sensor prototype with potential for batch fabrication. A thin Tantalum Pentoxide film was deposited on the tip of a polished sapphire fiber using electron-beam evaporation. Using low-coherence optical interferometry, the film was tested as a temperature sensor from 200°C to 1000°C, and its resolution was measured to be 1.4°C. In addition to its potential for low-cost batch production, the sensor´s ultra-miniature size of only 75 μm makes it ideal for embedded sensing applications in harsh environments.