Yb/Er-doped optical fibers for pulsed laser and optical amplifier applications

Compact laser sources require active materials able to provide high gain per unit length: phosphate glasses match these requirements thanks to the high solubility they offer for rare earth ions together with high emission cross sections and chemical stability. The scope of this study is the design, fabrication and characterization of Yb/Er double cladding optical fibers suitable for the development of compact lasers and optical amplifiers. The core and cladding glass compositions were fabricated and characterized in terms of thermal, mechanical and optical properties. Optical damage threshold for pump photons was also measured in order to validate the ability of the glass to withstand high intensity sources. Preforms were fabricated by rod-in-tube technique, with the cladding tubes being obtained by rotational casting. Various types of optical fiber configurations were drawn and characterized. They showed good quality of interfaces between its components and an attenuation loss of 2 dB/m was measured by cut-back method. Optical amplification was demonstrated both by core and cladding pumping thus demonstrating its suitability to fabricate compact optical devices.