A novel design for a high brightness diode pumped fiber laser source

Lasing action is reported in a new type of fiber design, The fiber consists of an undoped core and a doped glass cladding surrounded by a plastic coating. The refractive indices obey the relation n(clad)>n(core)much greater than n(coat). The refractive index/doping concentration distribution recommends to the designation M-profile fiber (MPF). The brightness and the output power of the MPF laser may at least be as high as that of a double clad fiber (DCF) laser. For the first properly working MPF laser the near and far field intensity distributions are reported along with measurements concerning the pump light distribution in the fiber, the output power, lasing spectrum and polarisation of the emitted radiation.