Sensitive Ho3+,Yb3+ co-doped mixed sesquioxide single crystal fibers thermometry based on upconversion luminescence

Abstract

Mixed sesquioxide crystals (R2O3, R = Lu, Y or Sc, where R is occupied by two different elements) have drawn an increasing attention due to their outstanding physical and chemical properties. In this work, we have grown Ho3+,Yb3+ co-doped mixed sesquioxide LuYO3 and LuScO3 single crystal fibers (SCFs) in centimeter-length by laser heated pedestal growth (LHPG) method for optical temperature sensing. Both mixed sesquioxide SCFs yield strong green emission (5F4,5S2→5I8) and weak red emission (5F5→5I8) under the excitation of 980 nm laser. Their upconversion (UC) levels are not thermally coupled levels (NTCL). Importantly, these mixed sesquioxide SCFs show a good temperature sensitivity in the temperature range of 298–748 K. Using UC fluorescence intensity ratio (FIR) method, the calculated maximum values of absolute sensitivity of Ho,Yb:LuYO3 and Ho,Yb:LuScO3 are 0.1603 (at 303 K) and 0.0886 K−1 (at 300 K), respectively. These features indicate that our grown mixed sesquioxides show a great potential for high-sensitivity temperature sensing applications. Furthermore, the presented mixed sesquioxide SCFs are excellent candidates for the high-integrated temperature sensor.