Quantitative Determination of Sources of the Electro-Optic Effect in LiNbO3and LiTaO3

Ultrafast zone-center coherent lattice dynamics in ferroelectric lithium tantalate

“…The excitation of coherent phonons basically obeys the Raman selection rule, that is, all excited coherent phonons are Raman active. There is a disagreement in the literature on the assignment of the long-wavelength optical phonons in LiTaO 3 [5][6][7][8][9][10], [15][16][17][18][19]. Our assignment is mainly based on the Raman results by Kaminow and Johnston [15], which are further supported by the first-principle calculations [20].…”

A theoretical model of the linear electro-optic effect

“…Kaminow derived a simple relation between an electro-optic coefficient measured at radio frequencies and the corresponding Raman-scattering efficiencies . Using the measured efficiencies, he calculated the electro-optic coefficients of LiNbOs and LiTaOs, which are in good agreement with experiment (Kaminow and Johnston 1967). With the macroscopic equations between polarisation, ion displacement and electric field, Kelly (1966) found an expression for the coefficient of zincblende crystals.…”

Determination of the Raman Polarisabilities of Optical Phonons in Lithium Niobate Uniaxial Single Crystal

“…Figure 2a described the angular behaviour of the areas under the 633cm -1 peak according to (1) while in figure 2b is presented the enhancement of the 369,5 cm -1 line of the 2 E symmetry type using (2). We have reported in table I, the calculated Raman polarisabilities for the above mentioned examples (figure 2) in comparison with the published results concerning the LiNbO 3 crystal It can be noticed that the early experiments 8 were performed under the radiation of the 488nm line of ion argon laser. As can be observed, our preliminary results are in good agreement with ref.…”

“…for any angular position of polarisers, the integrated intensities of the Raman spectrum can be clearly analysed. The determination of the relative phases as well as the theoretical derivation of Raman polarisabilities tensor are news features which reveals the advantage of this method over others comparative methods (8,9) . Rotating crystal has also the advantage of moving only the sample support instead of rotating simultaneously the polarisers.…”

“…The advantage of the studies focussed on diatomic substances dwell on the simple character of their structure. Meanwhile, only few attempts were devoted to solid substances with more than two atoms such as lithium niobate 8 (LiNbO 3 or LN) and lithium tantalate 8 (LiTaO 3 or LT) on the one hand and lithium meta gallate 9 (LiGaO 2 ) on the other hand. Both studies used the 992 cm -1 Raman line of benzene used as the reference.…”