Optical temperature sensing of Yb,Er:GSAG single crystal in both upconversion and downconversion dual-mode luminescence

Fluorescence intensity ratio thermometry represents a novel non-contact approach for rapid and precise temperature measurements. In this study, a Yb,Er co-doped Gd3Sc2Al3O12 single crystal (Yb,Er:GSAG) was investigated, exploiting the dual-mode luminescence of upconversion and downconversion for optical temperature sensing applications. The crystal exhibited distinct luminescence behaviors when subjected to 266 nm, 355 nm, and 980 nm laser excitations, manifesting a dark blue appearance under 266 nm ultraviolet (UV) excitation and a green hue under 355 nm and 980 nm excitations. Specifically, under 355 nm excitation, the crystal demonstrated a predominantly pure green upconversion, with a green-to-red ratio of 38. For the first time, we propose an investigation into the temperature sensing behavior under dual-mode luminescence in the same crystal, utilizing the fluorescence intensity ratio of the 2H11/2 and 4S3/2 thermally coupled energy levels of Er3+. The obtained maximum relative sensitivities (SR) for the two fitted luminescence modes were found to be 101.80×10−4 K−1 at 300 K (980 nm excitation) and 126.39×10−4 K−1 at 300 K (355 nm excitation), respectively. The impressive SR values substantiate Yb,Er:GSAG crystal as highly promising candidates for optical temperature sensing applications. [Display omitted] •Yb,Er:GSAG single crystal grown by Cz method was employed for optical temperature sensing applications.•The optical temperature sensing behavior of Yb,Er:GSAG single crystal was exploited.•The maximum relative sensitivities SR were found to be 101.8×10−4 K−1 (980 nm excitation) and 126.4×10−4 K−1 (355 nm excitation) at 300 K, respectively.•The impressive SR values substantiate Yb,Er:GSAG crystals promising for optical temperature sensing applications.