Room temperature infrared-laser-induced upconversion in Nd3+ doped Ta2O5 waveguides

The room temperature infrared to visible upconversion properties of Nd3+ doped Ta2O5 rib waveguides deposited on a silica substrate have been investigated in the 720-900 nm excitation range. Two possible upconversion mechanisms exist at different excitation wavelengths. The main one is due to energy transfer upconversion and results in the population of the 4G7/2 level. Radiative relaxations from this level to the 4I9/2, 4I11/2 and 4I13/2 multiplets produce visible emission bands in the green, orange and red regions. Excited state absorption from the 4F3/2 to the 2P1/2 state can also occur, giving rise to a blue emission band (2P1/2 → 4I9/2). A rate equation analyses supports the proposed mechanisms.