Photo-induced birefringence in semiconductors compared with optical fibers

We analyze the photon-induced birefringence in semiconductors based on pump-probe setups, within the semiconductor Bloch equations formalism and the Luttinger–Kohn model for the band structure. When the pump and probe pulses are well separated in time, the anisotropic momentum space filling of the photo-excited electrons is the only mechanism causing the induced birefringence. The birefringence ratio is then Br=34 for pump and probe having perpendicular vs. parallel linear polarizations. This ratio is Br=16 for opposite vs. identical circular polarization. When the pump and probe pulses overlap in time, these birefringence ratios become Br=13 for linear polarizations and Br=19 in case of circular polarizations. These predictions differ markedly from those for optical fibers.