NR 6/2016 INŻYNIERIA MATERIAŁOWA MATERIALS ENGINEERING 341 Erbium/Ytterbium co-doped oxyfluoride glass-ceramics — promising candidate for fiber lasers and optical amplifiers at 1550 nm Michał Żelechower * , Elwira Czerska, Elżbieta Augustyn Silesian University of Technology, Institute of Materials Science, * michal.zelechower@polsl.pl The manufacturing of the erbium/ytterbium co-doped oxyfluoride glass-ceramics optical fiber was discussed on the background of literature review and own achievements. The role of erbium ions as NIR emitters as well as ytterbium ions in the process of stimulated emission has been explained and illustrated by several figures both from the literature and the author’s results. Glass-ceramics material advantage over glassy fibers was also considered and proved by several plots and images. The relations between the g-c materials and their optical features have been illustrated by results of SEM/TEM imaging, X-ray spectra, XRD and SAED patterns, thermal analysis (DTA/DSC) and a corresponding absorption/emission NIR spectra. Key words: fiber laser, rare earth ions, glass-ceramics, edfa, nanocrystals. Inżynieria Materiałowa 6 (214) (2016) 341÷349 DOI 10.15199/28.2016.6.11 © Copyright SIGMA-NOT MATERIALS ENGINEERING 1. INTRODUCTION A chance to establish the long distance waveguide communications appeared in early seventies due to super pure low-loss fused silica glass optical fibers (about 90% of SiO 2 ) fabrication. Since silica fiber attenuation is wavelength dependent (Fig. 1), the term “optical fiber communication window” has been introduced and currently the third window (1550 nm) is utilized for long distance cables with attenuation better than 0.3 dB/km. In traditional optical communication systems a signal regenera- tion was achieved in the form of optoelectronic repeaters located every 20÷50 km of the fiber cable (Fig. 2). They used three steps of signal regeneration: optical-to-electric conversion, amplification, and shaping and finally electric-to-optical conversion. Currently, several more sophisticated solutions (optical amplifiers without sig- nal conversion) have been invented (EDFA – Erbium Doped Fiber Amplifier, SOA – Semiconductor Optical Amplifier, RFA – Raman Fiber Amplifier) and of them the EDFA amplifiers seem to be most common. Their heart is silica (plus GeO 2 ) glass erbium doped opti- cal fiber (Fig. 3). Actually, the EDFA amplifier structure is much more complex and contains additionally WDM devices (Wavelength Division Multiplexer — Bragg gratings) but EDFA details are beyond of the scope of the paper and will be skipped. 2. THE ROLE OF RARE EARTH ELEMENTS Why erbium doped glass fiber? The reason is comprehensible: the wavelength of the 4 I 13/2 → 4 I 15/2 transition in erbium about 1550 nm (stimulated emission) matches the third minimum of silica fiber at- tenuation plot (third window). In the same way the 1 G 4 → 3 H 5 tran- sition wavelength in praseodymium (1310 nm) corresponds to the second window and the PDFA (Praseodymium Doped Fiber Ampli- fier) are commercially available for application in local waveguide networks. Actually, several RE ions emission can be utilized in opti- cal amplifiers provided for various bands (Fig. 4). Transition scheme in erbium ion Er 3+ is shown in Figure 5. Ma- terial containing erbium ions can be optically pumped by 800 nm sources (for instance HeNe tunable laser) or by 980 nm sources (InGaAs laser diode) demonstrating ground state absorption (GSA) Fig. 1. Fused silica fiber attenuation curve (a) – [1], and telecommunication windows (b) – [2] Rys. 1. Krzywa tłumienia krzemionkowych włókien światłowodowych (a) – [1] oraz okna telekomunikacji (b) – [2] a) b)