Ytterbium- and chromium-doped fibre laser: from chaotic self-pulsing to   passive Q-switching
  A spontaneously chaotic, self-pulsing ytterbium-doped fibre laser is partially stabilized into the passively Q-switched mode of operation using a chromium-doped saturable absorber fibre. This original all-fibre laser produces sustained and stable trains of smooth pulses at high repetition rate. 
Bernard Dussardier (LPMC), Jerome Maria (LPMC), P. Peterka
physics.optics