Energy transfer among rare earth ions induced by annealing process of TmEr codoped aluminum oxide thin films

ErTm codoped amorphous aluminum oxide (a-Al2O3) thin films have been prepared by pulsed laser deposition. Efficient photoluminescence (PL) in the region of 1400–1700 nm with two peaks centered at 1533 nm and 1620 nm were observed with pumping at the wavelength of 791 nm. The PL performance has been investigated as a function of annealing temperature, which was varied from 650 to 850 °C in air. Infrared emission was improved by annealing, and energy transfer processes occurred obviously for annealing temperatures between 800 and 850 °C. All possible energy transfer channels were investigated and our results suggest that the quasi-resonant energy transfer and cross relaxation between Tm3+ and Er3+ play an important role in the evolution of the luminescent response.