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Communication Dans Un Congrès Année : 2012

New design for passive coherent coupling of fiber lasers

François Jeux
  • Fonction : Auteur
  • PersonId : 929318
Agnès Desfarges-Berthelemot
Vincent Kermène
Alain Barthélémy
David Sabourdy
  • Fonction : Auteur
Jean-Eucher Montagne
  • Fonction : Auteur

Résumé

Passive techniques for coherent coupling of lasers offer an appealing way for the generation of high brightness laser beam because of their simplicity and their all-optical operation. Many configurations have been investigated and it has been shown that coherent coupling becomes less efficient as the size of the laser array increases. This is the reason why research in that field focused on some way to overcome the threshold size of about 10 with good efficiency. In that context we proposed a new cavity design, combining optical nonlinearity, and the use of a specific spatial filter. The nonlinearity considered here, due to the contribution of the population inversion to the optical phase in the amplifiers is significantly larger than the non resonant Kerr non linearity of silica in fiber amplifiers. It is usually assumed that the nonlinear phase shift evolves linearly with the gain (Kramers-Krönig). We made experiments using an Ytterbium doped fiber amplifier which confirm an almost linear relationship whatever the pump level. We suggested transforming the phase deviations into power deviations so that the gain can vary from one channel to another. Therefore a gain-dependent phase introduced during amplification can compensate for the linear phase delay between the different laser fields. We proposed to use the set-up of phase-contrast microscopy due to Zernike. A phase plate inserted in the far field performs the phase to amplitude conversion. To assess the potential of the new scheme we have used some numerical simulations. Starting from noise our model reproduces the laser modes build-up until steady state giving the final laser frequencies and spatial pattern. Numerical results that will be reported show a gain in efficiency by comparison with previous passive coupling schemes. Preliminary experiments are under way to confirm the theoretical expectations.
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Dates et versions

hal-00725746 , version 1 (27-08-2012)

Identifiants

  • HAL Id : hal-00725746 , version 1

Citer

François Jeux, Agnès Desfarges-Berthelemot, Vincent Kermène, Alain Barthélémy, David Sabourdy, et al.. New design for passive coherent coupling of fiber lasers. SPIE Security + Defense, Sep 2012, Edimbourg, United Kingdom. Paper 8547-23. ⟨hal-00725746⟩

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