Abstract

For many applications in telecommunication, sensing, and spectroscopy reliable all-solid-state laser light sources are desirable. Using the great variety of ionic dopands of the lanthanides the spectral range between 0.9 and 3 µm 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 fibers¹ 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.² 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. The refractive indices obey the relation n_clad> n_core≫n_coat The refractive index/doping profile of this fiber recommends to the designation M-profile fiber (MPF). Its design and the construction data are plotted in Fig. 1.

© 1996 Optical Society of America