Energy Transfer and Avalanche Upconversion of Nd x Y 1− x VO 4 Nanocrystals

We explore Nd concentration and excitation power dependences of the avalanche upconversion of Nd x Y 1– x VO 4 ( x = 0–1) nanocrystals with uniform size and shape. The avalanche threshold power caused by the near-resonant energy transfer between 4 F 5/2 → 4 I 13/2 and 4 F 5/2 → 2 G 9/2 significantly decreases as the Nd 3+ concentration increases. The off-resonant energy transfer between 4 F 5/2 → 4 I 13/2 and 4 F 5/2 → 4 G 11/2 in the strong excitation regime leads to apparent broadening on the blue-side of the upconversion spectrum of NdVO 4 nanocrystals.