Upconversion emission from amorphous Y2O3:Tm3+, Yb3+ prepared by nanosecond pulsed laser irradiation

► Film of amorphous Y2O3:Tm3+, Yb3+ is prepared by ns pulsed laser irradiation. ► The film present strong blue upconversion emission. ► The relative intensity of the blue emission to the infrared one is an order of magnitude higher than that of the bulk material. ► The enhancement of the blue upconversion is attributed to the longer lifetime of the levels of the doped ions.