Comments on index nomenclature equivalencies for uniaxial materials (i.e. birefringent or two independent indices of refraction):

The following two expressions are equivalent:
1) ordinary ray, (n_o,n_w, or w),
2) E-field perpendicular to c axis (n^ )


The following two expressions are equivalent:
1) extraordinary ray (n_e, n_e, or e)
2) E-field parallel to c axis (n // )

---

(The c axis is also known as the optical axis.)

Luxpop returns the absolute refractive index (i.e. with respect to vacuum) , unless stated otherwise.