International
Tables for Crystallography Volume D Physical properties of crystals Edited by A. Authier © International Union of Crystallography 2006 |
International Tables for Crystallography (2006). Vol. D. ch. 1.7, p. 187
Section 1.7.3.1.4.2. Propagation out of the principal planes
a
Laboratoire de Spectrométrie Physique, Université Joseph Fourier, 140 avenue de la Physique, BP 87, 38 402 Saint-Martin-d'Hères, France, and bLaboratoire de Photonique Quantique et Moléculaire, Ecole Normale Supérieure de Cachan, 61 Avenue du Président Wilson, 94235 Cachan, France |
It is impossible to define ordinary and extraordinary waves out of the principal planes of a biaxial crystal: according to (1.7.3.6) and (1.7.3.9), e+ and e− have a nonzero projection on the z axis. According to these relations, it appears that e+ and e− are not perpendicular, so relation (1.7.3.10) is never verified. The walk-off angles ρ+ and ρ− are nonzero, different, and can be calculated from the electric field vectors: or for a positive or a negative optic sign, respectively.