Bistable chromatic switching in Yb3+ doped NdPO4 crystals

Pump-induced chromatic switching is reported for an 808 nm pumped Yb3+-doped NdPO4 crystal. This effect is based on the interplay between the Nd3+↔Yb3+ energy transfer processes and on the large pumpinduced thermal loading characteristic of this neodymium compound. For temperatures below 300 K, a noticeable hysteresis is observed in the relative Nd3+ and Yb3+ contributions to the emission spectra; this leads to a bistable chromatic switching. This optical bistability is related to a nonlinear pump-induced heating rate that produces abrupt changes in the local temperature.