On the nature of photoluminescence in Bismuth doped silica glass
Résumé
We report on the investigation of Bismuth-doped pure silica glass without other co-dopant by the
tech- nique of magnetic circular dichroism (MCD), which allows the direct probing of the ground state of
optical centres. Taking into account the results of conventional optical spectroscopy, we show that the
observed MCD bands belong to the centre responsible for the red photoluminescence in this material.
Measurements of the temperature and field dependences indicate that the MCD effect is caused by the
even-electron system. This, however, opposes the widespread opinion that Bi2+ ions are the origin of
red photoluminescence in Bismuth-doped silica glasses. On the other hand, the lasing centre responsible
for the near infrared photoluminescence does not exhibit any magnetic optical activity connected
to its ground state. As a consequence, we conclude that the ground state of lasing centre is a magnetic
singlet with the effective spin S = 0.