Raman Scattering Of Light On Overtone States Of Transverse And Longitudinal Polar Optical Modes In A Single Crystal Of Lithium Tantalate

Raman scattering spectra in single crystals of lithium tantalate at 180-degree scattering geometry in a wide spectral frequency range (50 divided by 2800 cm(-1)) were studied. Raman peaks were found in 1300 divided by 2000 cm(-1) region with frequencies exceeding doubled frequencies of LiTaO3 crystal lattice fundamental vibrations of A(1) and E-type. The conditions for the manifestation of bound polar phonons in lithium tantalate Raman spectra were analyzed. The spectral intensity of Raman scattering in the overtone region of the spectrum of lithium tantalate was calculated taking into account the presence of a biphonon, and a satisfactory agreement between theory and experiment was obtained.