Phosphate double cladding optical fibers for short cavity pulsed lasers

Phosphate glasses are interesting materials for the fabrication of double cladding optical fibers suitable for pulsed lasers in the near infrared wavelength region. The fabrication of Nd, Yb and Yb/Er doped phosphate glasses will be reported together with the characterization of their thermal and optical properties. Suitable passive glasses for 1st and 2nd cladding were manufactured with the aim of obtaining the designed numerical apertures while maintaining well-matched physical properties for stress-free configurations. Preform fabrication by means of rotational casting will be discussed and compared to traditional rod in tube technique in particular regarding the interfaces between core and 1st cladding and between 1st and 2nd cladding. Double cladding optical fibers will be presented and characterized in terms of attenuation loss via cutback method. The demonstration of laser emission will follow by employing fiber pigtailed laser diodes for the excitation of the rare earth ions