Phosphate glass optical fibres for CW and pulsed lasers

Phosphate glasses display high solubility of rare earth ions, high emission cross sections, and low non-linear refractive index. These features make them suitable candidates for the realization of compact high peak power pulsed optical lasers and amplifiers. The fabrication and characterization of rare earth doped double cladding phosphate optical fibres is reported. The optical fibres were drawn from preforms obtained by rod-in-tube techniques where cladding tubes were fabricated by rotational casting, thus assuring good interface quality and proper core-cladding geometries. Investigated rare earth dopants included Nd3+, Yb3+ and Er3+ ions. Laser action at 1054 nm was demonstrated by cladding pumping a 9 cm long Nd-doped fibre. Yb-doped fibres showed lasing at the wavelength of 1014 nm over a length of 25 mm. A net optical gain of 16 dB at the wavelength of 1554 nm was obtained by cladding pumping a 9 cm long Yb/Er optical fibre.