Luminescence of Ni2+ and Cr3+ centres in MgSiO3 enstatite crystals

Emission and excitation spectra and luminescence decay curves of enstatite MgSiO3 single crystals nominally doped with Ni and Cr have been measured at temperatures down to 10 K. For all the crystals under investigation, the emission band peaking at about 1520 nm is assigned to the T-3(2) --> (3)A(2) transition of octahedral Ni2+ centres, whilst the luminescence around 800 nm is assigned to the T-4(2) --> (4)A(2) transition of octahedral Cr3+ centres. Chemical analysis has confirmed the presence of Ni impurities in the nominally Cr doped crystals, and Cr impurities in the nominally Ni doped crystals. The peak stimulated emission cross section of the 1520 nm emission of Ni2+ is 3 x 10(-20) cm(2).