Pump-Polarization Dependence of the Bipolarization Emission in Ytterbium Lasers

Ytterbium lasers are widely used for femtosecond pulse generation, in particular for dual-comb spectroscopy. Indeed, in the case of quasi-isotropic active media such as Yb:YAG or Yb:CaF2, two eigenstates with orthogonal polarizations can oscillate simultaneously, corresponding to two frequency combs with adjustable repetition rates [1]. In order to balance the powers of the two modes, one may wonder if the use of a polarized pump could create a gain dichroism, as it has already been demonstrated in neodymium lasers. To this aim, we have performed experimental studies on Yb-doped solid-state lasers, that were supported by a two-mode rate-equation model taking into account the pump-induced gain anisotropy.