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Optical properties of phosphorus-related point defects in silica fiber preforms

  • Autori: Origlio, G.; Messina, F.; Cannas, M.; Boscaino, R.; Girard, S.; Boukenter, A.; Ouerdan, Y.
  • Anno di pubblicazione: 2009
  • Tipologia: Articolo in rivista (Articolo in rivista)
  • Parole Chiave: Silica; point defects; Phosphorus; absorption; photoluminescence
  • OA Link:


We report an experimental study on phosphorus-related point defects in amorphous silica, based on photoluminescence, absorption, and electron spin resonance measurements carried out on P-doped SiO2 fiber preforms. By photoluminescence measurements excited by laser or synchrotron light we detect an emission band peaked at 3.0 eV with a lifetime in the range of ms. The excitation spectrum of the 3.0 eV emission consists of two transitions peaked at 4.8 and 6.4 eV, the former giving rise also to a measurable absorption band. We attribute this optical activity to a P-related point defect embedded in SiO2, based on the spatial correlation between the emission intensity and the P doping level. A detailed spectroscopical investigation allows us to propose a scheme of the electronic levels of this P-related defect, in which the 4.8 and 6.4 eV excitation channels arise from transitions from the ground to two-excited singlet states, while the long-lived 3.0 eV emission is associated to a spin-forbidden transition from an excited triplet to the ground state. Finally, electron spin resonance measurements on X-irradiated samples lead us to propose a tentative microscopic model of the defect as a diamagnetic four-coordinated P impurity substitutional to a Si atom.