Green up-conversion emission in LaAlO3 crystal doped with holmium ions

Anti-Stokes intense green emission was observed after direct excitation of the 5F5 level of Ho3+ in LaAlO3. Up-conversion was observed due to strong Excited State Absorption (ESA), in which two intermediate levels the 5I7 and the 5I6, were involved. Power dependence of the antistokes emission depends on excitation wavelengths. The mechanism of the ESA is discussed in details.