Consider an anisotropic medium described by relative electric permittivity
Therefore, the propagation of the electromagnetic field is described by the curl-curl equation
where Φ , p , and q are shown in Table 6.
| Φ | p | q |
| E | 1 | ε ˜ |
| E | ε–1 ˜ |
 1 |
Table 6:  Definitions of Φ , p , and q for full- vector wave analysis