Eigenfrequencies and Eigenvectors of Polaritons with Application to LiNbO3 I. Long Optical Phonons
Open Access
- 1 April 1971
- journal article
- research article
- Published by Walter de Gruyter GmbH in Zeitschrift für Naturforschung A
- Vol. 26 (4) , 653-660
- https://doi.org/10.1515/zna-1971-0405
Abstract
The properties of polaritons in uniaxial crystals with an arbitrary number of atoms in the unit cell are discussed in the harmonic approximation. For LiNbO3 , which seems to become a very important substance for applications in tunable Raman lasers, the complete set of eigenfrequencies and eigenvectors (normal coordinates, electric field, electric polarisation) is calculated numerically. In the limiting case k→∞ (long optical phonons), which is treated in detail in this first paper, an example for each possible type of extraordinary phonon branches is discussed, namely a (T→L) -a (L→T)-, a (T→T)-and a (L→L) -branch of each type. The results are comparable with experimental data only for the frequencies of the 45°-phonons, measured by Barker and Loudon. The agreement is very satisfactory.Keywords
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