On the nature of photoluminescence in Bismuth-doped silica glass

Oleksii V Laguta,Igor M Razdobreev,Mohamed Bouazaoui,Vladimir B Arion,Hicham El Hamzaoui

doi:10.1038/s41598-017-03464-8

Abstract

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 responsi- ble 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.

Highlights

Bismuth-doped glasses are the subject of great research interest due to their potential applications for the development of new fiber amplifiers and tunable laser sources
Because the identification of the nature of this near infrared (NIR) PL is crucial for further development of efficient light sources, research efforts have been devoted to the elucidation of the nature of active NIR-luminescent centre and a number of hypotheses have been proposed to explain the origin of NIR PL in Bismuth-doped materials
The second very interesting and somewhat unexpected result is that the ground state (GS) of centre responsible for the red PL in this glass is not just a magnetic multiplet corresponding to the half-integer effective spin, but it is split in a zero magnetic field

Summary

Introduction

Bismuth-doped glasses are the subject of great research interest due to their potential applications for the development of new fiber amplifiers and tunable laser sources. Recently[12], we used magnetic circular polarization of luminescence (MCPL) to investigate Bismuth-doped silica glass without other co-dopant This technique enables the study of excited states (ES). The absence of the electron paramagnetic resonance (EPR) signal in Bismuth-doped silica glass is likely to contradict this assumption In this regard, the goal of the present paper was to clarify the spin multiplicity of the GS of both centres, the lasing one (responsible for the NIR PL) and the red PL emitting centre, by the magnetic circular dichroism (MCD). The third, diamagnetic -term, is due to the excited state degeneracy and it is temperature independent Due to these MCD term properties, this technique allows to investigate the nature of the GS of paramagnetic centre by measuring the temperature and magnetic field dependences of the MCD signal. This means that the Bi2+ ions are absent in this material

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