Near‐Infrared Thermometer Based on Stark Energy Levels of Yb3+ in Garnet

A Yb3+‐doped Gd3Al2Ga3O12 garnet (GAGG) Boltzmann thermometer is prepared and studied in this work. Due to the Boltzmann distribution of the population of Stark sublevels of Yb3+, the photoluminescence peaks of Yb3+ in the wavelength range of 950–1000 and 1000–1050 nm exhibit opposite temperature dependencies, which makes the luminescence intensity ratio (LIR) of two Yb3+ peaks work as a luminescence thermometer with a relative sensitivity of 1.6% K−1 at 200 K. It is worth nothing that this LIR value still follows the Arrhenius model at temperatures as low as 200 K. In these results, it is suggested that Yb3+‐doped GAGG thermometer can achieve high sensitivity for accurate temperature measurements. In addition, the accurate position of various Stark sublevels of Yb3+ in GAGG is obtained for the first time. In this work, it is confirmed that the Yb3+‐doped GAGG thermometer exhibits potential applications in the fields of microelectronics and biology.