Excitation powder dependent optical temperature behavior of Er^3+ doped transparent Sr_069La_031F_231 glass ceramics

The knowledge of the pump power for which the population of thermally coupled energy levels (TCL) changes with power increase is of valuable importance for optical temperature sensors. In this paper, novel Er³⁺ doped transparent Sr0.69La0.31F2.31 glass ceramics was fabricated successfully, and its structure is studied by XRD, TEM and HRTEM analyses. The ²H11/2/⁴S3/2, ⁴F9/2(1)/⁴F9/2(2), and ⁴I9/2(1)/⁴I9/2(2) levels of Er³⁺ are proved as TCL by analyzing the temperature dependent fluorescence intensity ratios. The spectrum split, thermal quenching ratio, population stability, and temperature sensitivity from three TCL are observed to be dependent on the pump power. A new fitting method has been developed to establish the relation between fluorescence intensity ratios and temperature. It is found that the combined use of ²H11/2/⁴S3/2 and ⁴F9/2(1)/⁴F9/2(2) as thermally coupled energy levels will get a more precise temperature reading from 62.7 K to 800 K with the help of low excitation power at 66.8 mW/mm².