Novel fiber design for efficient Nd-doped fiber lasers in the 1-5 W power range

Summary form only given. Using the great variety of ionic dopants of the lanthanides the spectral range between 0.9 and 3 /spl mu/m can be covered. The beam parameter product of high-power diode laser (arrays) used as pump sources call for the development of fibers with an adapted design. The recently introduced double-clad fibers are well suited to fulfill this demand. The appearance of whispering gallery modes in these fibers limits the absorption efficiency to about 50% in centered active core fibers. An improvement can be obtained using decentered cores, periodical bending, or mode scrambling. For optimizing the fiber design in order to increase the output power and absorption efficiency we have invented another fiber design to avoid the problem encountered with the gallery modes. The fiber consists of an undoped core of large diameter and a doped glass cladding surrounded by a plastic coating.