LITTLE KNOWN FACTS ABOUT BIREFRINGENT CRYSTAL.

各向异性透明晶体如方解石、石英等的折射率，是其固有的特性，称为永久双折射。All nonlinear crystals for nonlinear frequency conversion are birefringent. It's because they might have their nonlinearity only by remaining non-isotropic, Which also brings about birefringence.When these projections are then calculated a