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.