Upconversion dynamics in Er3+-doped YAG

Green, blue, violet and ultraviolet upconversion luminescence is reported at room temperature in a YAG: 10.5%Er3+ crystal pumped by one-colour (647 nm) and two-colour (647+618 nm) laser excitation. The upconversion mechanism was studied by means of time-resolved luminescence spectroscopy and the energy flow pathways are described. Based on the results it appears that energy transfer upconversion is the dominant contribution to the upconverted luminescence upon 647 nm excitation, and excited state absorption is the dominating mechanism upon 647+618 nm excitation.