birefringence from refractive index tensor
Birefringence is the difference in light speed in anisotropic material. When entering an anisotrpic media plane polarised light migrating along the propagation direction vprop is split into two orthogonally vibrating waves that moves at different speed, the slowest with nmax and the faster wave with nmax. The values of nmin and nmax can be calculated from the refractive index tensor containg the three pricipal refractive index of the mineral, nalpha, nbeta and ngamma and the ligth propagation direction (vprop) with repect to the crystal reference frame. The birefringence varies as function of the vprop and for each vprop coressponds to nmax-nmin.
|vprop||propagation direction vector3d|
|nMin||lowest refractive index for a given propagation direction|
|nMax||highest refractive index for a given propagation direction|
|n||difference between nMax and nMin|
|pMin||vector3d polarization direction with the lowest refractive index|
|pMax||vector3d polarization direction with the highest refractive index|