Experimental investigation on the upconversion mechanism of 754Â nm NIR luminescence of Ho3+/Yb3+:Y2O3, Gd2O3 under 976Â nm diode laserexcitation

► We demonstrate that the NIR emission (754 nm) is associated with the 5F4/5S2→5I7 transition of Ho3+ ions without the contribution of the 5I4→5I8 transition for Ho3+/Yb3+ codoped Y2O3 and Gd2O3 bulk ceramics. ► Population saturation in the 5I7 energy level has been observed in Ho3+/Yb3+ codoped Y2O3, Gd2O3 bulk ceramics. ► We demonstrate the result, the NIR emission (754 nm) is associated with the 5F4/5S2→5I7 transition of Ho3+ ions, by the steady-state rate equations.