X-Ray Diffraction Study of the X-112° Y-Cut of a LiTaO₃ Crystal Modulated by Surface Acoustic Waves

The process of X-ray diffraction on the X-112° Y-cut of a LiTaO₃ crystal excited by surface acoustic waves (SAW) with a wavelength of Ʌ=4 μm was studied at a synchrotron radiation source in a scheme of a double-crystal X-ray diffractometer. The sinusoidal acoustic modulation of the crystal lattice leads to the appearance of diffraction satellites on the rocking curve; the number and intensity of satellites depend on the amplitude of the SAW. Analysis of X-ray diffraction spectra allowed us to determine the velocity (VSAW=3300 m/s) and amplitudes of the SAW. For the first time experimental investigations have demonstrated the presence of the power flow angle in the X-112° Y-cut of a LiTaO₃ crystal, i.e., a situation where the direction of acoustic energy propagation (PFV) does not coincide with the direction of the SAW wave vector KSAW. The measured power flow angle was PFA=0.41°. This PFA value is important for designing acoustoelectronic devices in order to reduce acoustic signal losses.