Europhys. Lett., 71 (3), pp. 394–399 (2005) DOI: 10.1209/epl/i2005-10092-4 EUROPHYSICS LETTERS 1 August 2005 Self-absorption and radiation trapping in Er 3+ -doped TeO 2 -based glasses M. Mattarelli 1 ( * ), M. Montagna 1 , L. Zampedri 1 , A. Chiasera 2 , M. Ferrari 2 , G. C. Righini 3 , L. M. Fortes 4 , M. C. Gonc ¸alves 4 , L. F. Santos 4 and R. M. Almeida 4 1 Dipartimento di Fisica, Universit` a di Trento, GCSMFO Via Sommarive 14, I-38050 Povo, Trento, Italy 2 IFN-CNR, Istituto di Fotonica e Nanotecnologie, GCSMFO Via Sommarive 14, I-38050 Povo, Trento, Italy 3 IFAC-CNR, Istituto di Fisica Applicata “Nello Carrara” Via Panciatichi 64, I-50127 Firenze, Italy 4 Departamento de Engenharia de Materiais, Instituto Superior T´ ecnico A. Rovisco Pais, 1049-001 Lisboa, Portugal received 13 January 2005; accepted in final form 1 June 2005 published online 6 July 2005 PACS. 42.70.Hj – Laser materials. PACS. 78.55.-m – Photoluminescence, properties and materials. PACS. 78.40.-q – Absorption and reflection spectra: visible and ultraviolet. Abstract. – The 1.5 µm fluorescence shape and lifetime of Er 3+ -activated tellurite glasses have been investigated. The measures on bulk system have been compared with those obtained on powders, showing that the self-absorption effect broadens the emission spectrum and lengthens the lifetime. It has been demonstrated that the bandwidth and lifetime measurements depend on the absorption coefficient α(λ) and on the distance d between the focused exciting laser beam and the exit face of a bulk glass sample. The actual emission spectrum has been reconstructed from the α(λ) · d knowledge. Lifetime lengthening cannot be determined from α(λ) · d and, to obtain actual lifetime for highly Er 3+ -doped glasses, measurements on powders are required. The design of erbium-doped broadband amplifiers requires the measurement of the 4 I 13/2 → 4 I 15/2 effective transition bandwidth and lifetime. This paper discusses the measurement of these parameters in the presence of self-absorption and indicates an experimental procedure to obtain their actual value. A series of glasses with nominal molar composition 60TeO 2 –20ZnO–20ZnCl 2 –xErCl 3 , where x = 1, 3, 5, 10 (sample label: T1, T3, T5, and T10, respectively) were prepared as described in [1]. Figure 1 shows the normalized absorption spectra of T1 and T10 samples, measured by a double-beam spectrometer with a resolution of 2 nm in the region of the 4 I 13/2 → 4 I 15/2 transition of the Er 3+ ion. The normalized absorption spectra of T3 and T5 samples are very ( * ) E-mail: mattarel@science.unitn.it c  EDP Sciences Article published by EDP Sciences and available at http://www.edpsciences.org/epl or http://dx.doi.org/10.1209/epl/i2005-10092-4