Optical activation of Er3+ in Al2O3 during pulsed laser deposition

Erbium doped Al2O3 thin films have been prepared by alternate pulsed laser deposition on substrates either at room temperature (RT) or heated up to 600 °C. The Er related photoluminescence intensity at 1.53 μm is enhanced by two orders of magnitude and the lifetime is increased by up to a factor of 6 when the films are deposited at temperatures ⩾400 °C compared to the film grown at RT. The full width at half maximum (FWHM) of their emission spectra is as wide as 60 nm, consistently with the amorphous nature of the Al2O3 host. The Er photoluminescence emission in the film deposited at RT can be enhanced by post-deposition annealing at high temperature (850 °C) to achieve similar peak photoluminescence intensity and lifetime values. However, its FWHM is only 40 nm. Analysis of the photoluminescence response after post-deposition annealing treatments suggest that the microstructure of the amorphous Al2O3 host grown at temperatures ⩾400 °C is different from that of films grown at RT, and seems to be more stable upon annealing.