A detailed study of the optical spectroscopy of Er3+ in Ca3Ga2Ge3O12 crysta
ls is reported. Several site selective techniques were employed (absorption
, luminescence, excitation and up-conversion). The combined use of these te
chniques allowed the separation and classification of the observed spectral
lines. Six different Er3+ optical centres are observed. The energy level a
nalysis was performed using a parametric Hamiltonian for the 4f(11) electro
nic configuration of Er3+ in a D-2 symmetry site. A set of parameters was o
btained by fitting calculated to experimental energy levels for each identi
fied centre. Differences among centres were analysed and related to the dif
ferent charge compensating mechanisms.