Upconversion luminescence of a calcium sodium aluminosilicate glass doped with erbium.

The visible and upconversion luminescence of an erbium doped calcium sodium aluminosilicate (CSAS) glass was investigated at room temperature and 77 K. Upconverted visible luminescence was observed upon excitation in the red (»exc=650 nm) and NIR (»exc=800 nm) regions of the spectrum. The intensity of the upconverted visible luminescence was relatively weak compared to that obtained upon direct excitation (»exc=488 nm) owing to efficient multiphonon relaxation, a result of the high phonon energies of the aluminosilicate host. A two-photon upconversion process was proposed via two independent pathways: excited state absorption (ESA) and energy transfer upconversion (ETU).