ABSTRACT
An optical crystal is an anisotopic dielectric and the dielectric tensor of such a crystal in a coordinate system that coincides with the principal axes of the crystal will have zero off-diagonal elements and is given by ε ¯ = ε 1 0 0 0 ε 2 0 0 0 ε 3 . https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315272351/41040b79-9956-496a-ac34-683fa4364729/content/eqn12_1.jpg"/>
