Nonreciprocal light transmission in silicon by Raman-induced asymmetry of the permittivity tensor

We consider the effect of Raman-induced nonreciprocal light transmission in silicon and show that it can be understood as the consequence of the asymmetry of an effective permittivity tensor at the Stokes wavelength. This viewpoint enables the derivation of a necessary condition for this effect: the pumping electric field must have components along two different crystallographic axes which are oscillating out of phase with respect to each other.