1 Erratum to: Appl Phys B (2012) 106:409–417 DOI 10.1007/s00340-011-4691-0

Unfortunately there has been an error in the references.

Ref. 21 has to be as follows:

21. P. Koopmann, R. Peters, K. Petermann, G. Huber, Crystal growth, spectroscopy, and highly efficient laser operation of thulium-doped Lu2O3 around 2 μm, Appl. Phys. B 102, 19–24 (2011)

The citation of ref. 21 in paragraph “3.4 Cathodoluminescence” has to be deleted.