Low temperature optical sensor based on non-thermally coupled level of Ho3+ and defect level of Zn2+ in Yb3+:Y2Ti2O7 phosphor

Abstract

In this paper, non-contact optical low temperature sensing behavior is explored between non-thermally coupled level of Ho3+ and the defect level of Zn2+ ion on doping in Yb3+:Y2Ti2O7 phosphor for the first time. The Ho3+/Zn2+ co-doped phosphor prepared by solid state reaction method demonstrates a temperature dependent behavior of emission intensity below the room temperature (25 °C). Under 450 nm (diode laser) excitation, the fluorescence at 552 nm (Green) and 754 nm (NIR) from Ho3+ ions and at 713 nm (NIR) from defect level of Zn2+ ions has been observed and studied at different temperatures in between 300K-100K. An enhancement in the emission intensity of defect band along with Ho3+ ions emission bands is observed on lowering the temperature. The ratio of emission intensity of peaks from Ho3+ level and defect level is considered for temperature sensing by polynomial fitting in FIR technique. The emission intensity of defect band increases with a larger rate than Ho3+ ions emission bands which increase the temperature sensor sensitivity. This paper opens a new field to use defect emission as a low temperature sensor. Thus, the present phosphor may be used as a low temperature sensing device.