PHILOSOPHICAL MAGAZINE B, 2002, VOL. 82, NO. 5, 573±585 A comparative study of the spectroscopic properties at 1.5 l m of erbium-activated ¯uoride and tellurite glasses R. Rolli y, M. Montagna, A. Chiasera Dipartimento di Fisica and Istituto Nazionale per la Fisica della Materia, UniversitaÁ di Trento, Via Sommarive 14, 38050 Povo, Trento, Italy G. C. Righini, S. Pelli Dipartimento di Optoelettronica e Fotonica, Istituto di Ricerca sulle Onde Elettromagnetiche, Consiglio Nazionale delle Ricerche, Via Panciatichi 64, 50127 Firenze, Italy A. Jha Department of Materials, University of Leeds, Leeds LS2 9JT, UK V. K. Tikhomirov, S. A. Tikhomirova Mechanical Materials Manufacturing Engineering and Management, Wolfson Building, University of Nottingham, Nottingham NG7 2RD, UK A. Monteil, S. Chaussedent Laboratoire ProperieÂte s Optiques des MateÂriaux et Applications, Unite Mixte de Recherche associeÂe au CNRS 6136, Universite d’Angers, 2 boulevard Lavoisier, 49045 Angers, France and M. Ferrari Consiglio Nazionale delle Ricerche, Centro di Fisica degli Stati Aggregati, Via Sommarive 14, 38050 Povo, Trento, Italy A bstract A comparative study of the spectroscopic properties at 1.5 mm of erbium- doped ¯uoride and tellurite glasses has been performed. Emission in the third telecommunications window has been observed upon excitation at 514.5 nm and the lifetime of the 4 I 13=2 level has been measured. Infrared-to-visible upconversion emission upon continuous-wave laser excitation at 976 nm has been detected in the di Œ erent hosts. The upconversion results in green and red emissions, whose intensity has a quadratic dependence on the excitation power. Lifetime measurements have been performed in order to clarify the contributions of excited-state absorption and energy transfer to the upconversion process. } 1. I ntroduction Fluoride and tellurite glasses are very attractive materials for photonics applica- tions, such as optical ampli®ers, frequency upconverters and lasers (Wang et al. Philosophical Magazine B ISSN 1364±2812 print/ISSN 1463±6417 online # 2002 Taylor & Francis Ltd http://www.tandf.co.uk/journals DOI: 10.1080/1364281011008522 6 y Email: rolli@science.unitn.it