Noninvasive optical temperature sensing behavior of Ho3+ and Ho3+/Er3+ doped tellurite glasses through up and down-converted emissions

Optical temperature sensing behavior of Ho3+ and Ho3+/Er3+ doped tellurite glasses are investigated in terms of fluorescence intensity ratio (FIR) method in the range of 298–558 K. Thermal studies reveal that proposed glasses are stable up to approximately 613 K. Optical thermometry investigations are carried out through temperature dependent up- and down-converted photoluminescence (PL) emissions. Richness of the up-converted PL spectrum provides versatility, therefore along with the down-conversion spectrum FIRs of four different emission band pairs are calculated and evaluated. Each pair demonstrates varying sensitivity values in the detectable temperature range. Pump power is altered in up-conversion regime from 0.45 to 0.90 W to investigate the rate of change of emission intensities. Reliability of the FIRs is confirmed after several heating-cooling cycles. Judd-Ofelt analysis is also adopted to estimate radiative properties and temperature sensing capabilities of the proposed glasses. The highest possible absolute and relative sensitivities are determined as 0.0172 K−1 and 2.48 % K−1, respectively indicating the potential of Ho3+/Er3+ doped tellurite glasses for their use in noninvasive optical temperature sensing applications.